EP1558535A1 - Crystallisable glass and the use thereof for producing extremely solid and break-resistant glass-ceramics having an easily polished surface - Google Patents

Crystallisable glass and the use thereof for producing extremely solid and break-resistant glass-ceramics having an easily polished surface

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Publication number
EP1558535A1
EP1558535A1 EP03757685A EP03757685A EP1558535A1 EP 1558535 A1 EP1558535 A1 EP 1558535A1 EP 03757685 A EP03757685 A EP 03757685A EP 03757685 A EP03757685 A EP 03757685A EP 1558535 A1 EP1558535 A1 EP 1558535A1
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EP
European Patent Office
Prior art keywords
glass
weight
temperature
ceramics
production
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Application number
EP03757685A
Other languages
German (de)
French (fr)
Inventor
Dirk Sprenger
Thilo Zachau
Rainer Liebald
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Schott AG
Original Assignee
Schott AG
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Publication date
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Publication of EP1558535A1 publication Critical patent/EP1558535A1/en
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Classifications

    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C3/00—Glass compositions
    • C03C3/04—Glass compositions containing silica
    • C03C3/062—Glass compositions containing silica with less than 40% silica by weight
    • C03C3/064—Glass compositions containing silica with less than 40% silica by weight containing boron
    • C03C3/068—Glass compositions containing silica with less than 40% silica by weight containing boron containing rare earths
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C10/00—Devitrified glass ceramics, i.e. glass ceramics having a crystalline phase dispersed in a glassy phase and constituting at least 50% by weight of the total composition
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C10/00—Devitrified glass ceramics, i.e. glass ceramics having a crystalline phase dispersed in a glassy phase and constituting at least 50% by weight of the total composition
    • C03C10/0036—Devitrified glass ceramics, i.e. glass ceramics having a crystalline phase dispersed in a glassy phase and constituting at least 50% by weight of the total composition containing SiO2, Al2O3 and a divalent metal oxide as main constituents
    • C03C10/0045—Devitrified glass ceramics, i.e. glass ceramics having a crystalline phase dispersed in a glassy phase and constituting at least 50% by weight of the total composition containing SiO2, Al2O3 and a divalent metal oxide as main constituents containing SiO2, Al2O3 and MgO as main constituents
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C10/00—Devitrified glass ceramics, i.e. glass ceramics having a crystalline phase dispersed in a glassy phase and constituting at least 50% by weight of the total composition
    • C03C10/0054—Devitrified glass ceramics, i.e. glass ceramics having a crystalline phase dispersed in a glassy phase and constituting at least 50% by weight of the total composition containing PbO, SnO2, B2O3
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C3/00—Glass compositions
    • C03C3/04—Glass compositions containing silica
    • C03C3/062—Glass compositions containing silica with less than 40% silica by weight

Definitions

  • the invention relates to a highly rigid, unbreakable, crystallizable glass of the magnesium-containing aluminosilicate type, a glass ceramic produced therefrom, which has a surface that can be polished well, and the use thereof in magnetic storage disks and mirror systems or as a substrate therefor.
  • Magnetic storage disks and magneto-optical storage materials as well as purely optical storage materials and mirror materials are subject to high demands in terms of breaking strength, high specific rigidity and high surface quality.
  • the growing demands placed on storage density and access speed, for example on hard drives, increase the mechanical loads that act on the substrate materials:
  • the speed of the storage disk In order to significantly reduce the access time, the speed of the storage disk must be increased to more than 15,000 rpm and the distance from Read head and disk surface can be lowered further.
  • support materials are required which have a high breaking strength (Klc and bending strength) and a very high modulus of elasticity or a very high specific stiffness and thus a low flutter amplitude.
  • the material has a very low surface roughness of Ra ⁇ 0.5 nm with a ripple of ⁇ 10 nm (ISO 1305 or DIN 4768).
  • the substrate or carrier material when producing a magnetic coating, the substrate or carrier material must have thermal loads in the range of withstand approx. 400 - 450 ° C and, due to high temperature changes, such as occur in sputtering processes, they are resistant to temperature changes.
  • the thermal expansion of the storage materials and mirrors should be adapted to that of the receiving device (spindle and spacers). These are currently made of steel, so that a thermal expansion coefficient of ⁇ 20 - 3oo of approx. 12 ppm / K is optimal, although smaller values can also be tolerated.
  • Aluminum alloys, glasses and glass ceramics are currently used as substrates for magnetic storage disks. Although glasses have a higher modulus of elasticity, they have the disadvantage of a low Klc value. This can only be improved to a limited extent by thermal or chemical hardening.
  • Glass ceramics also called vitroceramics, are polycrystalline solids which are produced by targeted devitrification, ie by crystallization from special glasses suitable for this purpose. This crystallization or ceramization is achieved by heating the glass bodies or, if appropriate, also by irradiation. there However, the glass-ceramic materials still contain a residual portion of a glass phase matrix in which the crystals are embedded.
  • glass ceramics in their glassy preliminary stage can be shaped into any shape using the usual glass-technical shaping processes and have many desired properties, such as resistance to temperature changes, low expansion coefficients and good electrical insulation, they are suitable for the production of a variety of objects, such as hobs , Dishes, high-voltage insulators, laboratory objects, bone replacements, or also for sealing environmentally harmful waste such as burnt nuclear fuel rods.
  • a well-studied system for the formation of glass or glass ceramics is the three-substance system Si0 2 -Al 2 0 3 -MgO (MAS system). Within this three-substance system there are various compositional areas in which differently specific crystalline phases exist or are stable or develop.
  • EP-A-0 289 903 describes a glass / ceramic-coated substrate which contains a composition of the above-mentioned three-substance system with a 42-68% weight fraction of SiO 2 .
  • JA-91045027 B (Nishigaki, J. et al.), JA-91131546 A (Tanabe, N. et al.), JA-92106806 A (Okubo, F. et al.)
  • EP 55 237 7 (Kawamura et al. ) describe different glass or glass ceramic compositions. However, these compositions contain no crystalline magnesium-aluminum-silicate phases or a lower SiO 2 content than 33% by weight.
  • EP-A-1 067 101, EP-A-1 067 102 and EP-A-0 941 973 describe yttrium-containing MAS glass ceramics as substrates for storage media. It states that the addition of 0.8-10 mol% yttrium oxide to a basic glass batch consisting of 35-65 mol% Si0 2 , 5-25 mol% A1 2 0 3 , 10-40 mol% MgO and 5-12 mol% Ti0 2 means that this glass can be melted more easily, has good mechanical properties and, after thermal treatment, the resulting glass ceramic has a modulus of elasticity of> 130 GPa.
  • the nucleating agent used is Ti0 2 , which continues to reduce the loss of glass parenz compensated within certain limits.
  • Y 2 0 3 serves as an additive to lower the processing temperature. However, a Y 2 0 3 content of> 10 mol% is undesirable because it increases the tendency of the glass to crystallize too much.
  • the usual glass ceramics usually contain enstatite, forsterite and cordierite as the main crystal phases. Spinel and sapphirine phases are also described as secondary phases.
  • the lower limit of the Si0 2 content is 35% by weight, with Si0 2 lower limits of 40 or 42-44% by weight being common. So far it has been assumed that below this Si0 2 concentration no technologically processable glasses can be produced.
  • JP-A-2000-327365 describes 25% by weight Si0 2 as the lower limit for alkali-containing glasses and 30% by weight in JP-A-11079785 for alkali-free glasses.
  • the aim of the invention is to provide new glasses which have a low SiO 2 content but which can nevertheless be processed using glass technology and which can be converted into glass ceramics which have a high modulus of elasticity.
  • Another object of the invention is to provide such a glass ceramic which can be polished to the desired surface roughness and which can be used as a substrate for magnetic storage disks or mirror systems.
  • glasses and glass ceramics can be produced which contain a small proportion of network-forming SiO 2 below the previously specified range of> 30% by weight and which are also suitable for Technical processing is suitable if Y 2 0 3 / Nb 2 0 5 and / or Ln 2 0 3 is added to this glass. It was also surprisingly found that such a glass is not only highly rigid and unbreakable, but also stable against the formation of crystalline phases prior to the targeted nucleation or ceramization, that is to say it can be cooled to relax. Such a glass ceramic can also be polished to the desired surface roughness of Ra ⁇ 0.5 nm.
  • the glass according to the invention or the glass ceramic obtained therefrom is formed from the three-substance system "Si0 2 -MgO-Al 2 0 3 " and additionally contains a proportion of B 2 0 3 .
  • the minimum amount of SiO 2 is 5% by weight, in particular 10% by weight, with 15% by weight being particularly preferred.
  • the upper limit is usually 33% by weight or 30% by weight, with 28% by weight and in particular 25% by weight being preferred.
  • the minimum amount of MgO is 5% by weight, preferably 8% by weight, 10% by weight being particularly preferred.
  • the upper limit of MgO is 25% by weight, with 20% by weight being preferred.
  • the A1 2 0 3 content is at least 25% by weight, preferably at least 30% by weight.
  • the maximum Al 2 0 3 content is 40% by weight and preferably 38% by weight.
  • Boron oxide does not necessarily have to be present, but the content of B 2 0 3 is often at least 1% by weight, usually at least 2% by weight and preferably at least 3% by weight, and the upper limit of B 2 0 3 is that The composition according to the invention at a maximum of 15% by weight, usually at a maximum of 12% by weight and preferably at a maximum of 10 or at most 9% by weight.
  • the oxides of the group Y 2 0 3 , Ln 2 0 3 and Nb 2 0 3 in the composition according to the invention are at least 0.1% by weight, usually at least 3% by weight and preferably at least 12% by weight.
  • the upper limit of these oxides is 30% by weight, preferably 28% by weight, an upper limit of 25% by weight is particularly preferred.
  • the amounts of the individual oxides are usually 0.1-30% by weight, preferably 10-30% by weight for Y 2 O 3 and 0-20% by weight or 0-20% by weight for Ln 2 0 3 .
  • Ln includes the lanthanoids, in particular La, Ce, Pr, Nd, Eu, Yb, Ho and Er.
  • composition according to the invention can contain, as further components, customary refining and fluxing agents, such as Sb 2 0 3 , As 2 0 3 , Sn0 2 , in the proportions customary for these purposes.
  • customary refining and fluxing agents such as Sb 2 0 3 , As 2 0 3 , Sn0 2 , in the proportions customary for these purposes.
  • Her upper limit is preferably max for Sb 2 0 3 or As 2 0 3 . 5% and preferably max. 2%.
  • the composition contains at least 2% by weight, preferably at least 4% by weight of TiO 2 and a maximum amount of preferably at most 12% by weight and in particular at most 10% by weight. If these are contained at all, the minimum amount for the other mentioned oxides Zr0 2 and ZnO is usually 1 or 2% by weight and the maximum amount is 5 or 8% by weight.
  • the glass according to the invention or the glass ceramic according to the invention is preferably essentially free of alkali oxides such as Li 2 0, Na 2 0 and K 2 0 and contains these only as impurities introduced with the remaining batch components.
  • Essentially alkali-free means an amount of at most 2% by weight, with at most 0.5% by weight being customary.
  • the glass or glass ceramic according to the invention can contain up to 10% by weight, usually ⁇ 5% by weight, of transition metal oxides without the resulting properties, such as rigidity, breaking strength and crystallization behavior, changing significantly.
  • transition metal oxides contained in the glass according to the invention or in the glass ceramic comprise the oxides of the elements Fe, Co, Ni, Cr, Mn, Mo, V, Pt, Pd, Rh, Ru and W and are in particular Mn0 2 , Fe 2 0 3 , NiO, CoO, Cr 2 0 3 , V 2 0 5 , M0O 3 and / or W0 3 .
  • the sum of the components SrO, BaO and CaO is at least 1% by weight, preferably at least 2% by weight and usually at most 5% by weight and in particular at most 4% by weight. If present, the proportion of the oxides Ti0 2 and Zr0 2 in an embodiment preferred according to the invention is at least 1% by weight, preferably at least 2% by weight and preferably at most 13% by weight, in particular at most 10% by weight.
  • the glass according to the invention or the glass ceramic according to the invention has a high modulus of elasticity of at least> 110 GPa.
  • the modulus of elasticity is usually above 120 Gpa.
  • glass ceramics with E-moduli above 150 Gpa, in some cases even> 200 Gpa can be produced.
  • the crystallites are embedded in a glassy matrix and more usually, but not necessarily, have a size of ⁇ 100 nm to approximately 3 ⁇ m.
  • crystallite sizes in the range of 50-500 nm are particularly preferred.
  • a glass ceramic is obtained from a glass composition according to the invention by crystallization and contains spinel, sapphirine and / or cordierite as the main crystal phases.
  • the desired properties of the glass ceramic are obtained when the crystals usually associated with high moduli of elasticity are obtained. tall phase entstatite, high or deep quartz and high quartz mixed crystals can be avoided, which is possible in particular with the composition according to the invention.
  • the glass ceramics obtained according to the invention can have crystals with a pyrochlore structure A 2 B 2 0 7 , in which A 3+ is a lantanoid and / or yttrium and B 4+ is Zr, Ti, Sn, and / or Ru.
  • they can contain pyrosilicates of the general formula A 2 Si 2 0 7 , in which A 3+ is a lantanoid, Y and / or Sc.
  • these are preferably Y 2 Si 2 0 7 (yttrium pyrosilicate, yttrialite) or Y 2 Ti 2 0 7 (yttropyrochloro).
  • the order in which the crystal phases are precipitated has a decisive influence on the modulus of elasticity. It has been shown that after the primary separation of small spinel crystallites and possibly small sapphirin crystallites, in particular those of the Mg 2 Al 4 SiO ⁇ 0 type , the subsequent secondary crystal phases of the sapphirin and cordierite type take place around the primary crystallites, in particular like a coating the primary crystallites. According to the invention, it was found that the SiO 2 content and the crystal structure of the secondary phase are dependent on the silicon and yttrium content of the base glass, a low SiO 2 content of the base glass promoting the formation of sapphirine.
  • the crystallite size of the primary crystals or the nuclei can be controlled in a targeted manner by the selection and content of the nucleating agents (Ti0 2 , Zr0 2 , P 2 0 5 ).
  • the size of the crystallites of the secondary phases can be controlled kinetically or thermodynamically (exploitation of diffusion and epitaxial phenomena).
  • Pyrochlores, pyrosilicates, xenotites and / or rutile are contained as tertiary crystal phases.
  • the residual glass phase fraction and thus also the modulus of elasticity of the resulting glass ceramic can be influenced by their elimination.
  • a glassy layer is formed with the glass according to the invention during the ceramization on the surface of the glass ceramic body, the thickness of which is significantly greater than the amount of residual glass remaining between the crystallites.
  • This glassy layer means that semi-finished products for storage substrates have a very low surface roughness. Since this glass phase is easier to polish than the deposited crystals, the post-processing effort is reduced considerably.
  • the glass according to the invention or the glass ceramic according to the invention also has very good mechanical properties, such as a high flexural strength (determined as a 3-point flexural strength according to DIN EN 843-1) of > 150 MPa, in particular> 180 MPa and a K 1C (determined according to AG Evans, EA Charles, J. Amer. Ceram. Soc. 59 (1976) 371) of> 1.3 MPam 1/2 .
  • a high flexural strength determined as a 3-point flexural strength according to DIN EN 843-1
  • a K 1C determined according to AG Evans, EA Charles, J. Amer. Ceram. Soc. 59 (1976) 371 of> 1.3 MPam 1/2 .
  • the glasses according to the invention are converted into the corresponding glass ceramic by thermal treatment at temperatures above Tg.
  • the transition temperature and the formation of crystal phases is determined by methods known per se, such as, for example, by means of a holding curve determined by means of differential thermal analysis (DTA).
  • DTA differential thermal analysis
  • the glasses are usually heated at a temperature of about 5-50 ° C. above Tg, preferably 10-30 ° C. above Tg, until sufficient primary crystallites have formed.
  • the usual glass transition temperature of these glasses is 700 - 850 ° C.
  • the holding time for the formation of the primary crystallites or crystal nuclei depends on the desired properties and is usually at least 0.5 hours, preferably at least 1 hour, with at least 1.5 hours being particularly preferred.
  • the maximum duration is usually considered to be 3 days, with 2 days and in particular 1 day being preferred as the maximum duration for the formation of the primary crystal nuclei. In most cases, a duration of 2-12 hours is sufficient.
  • the mixture is then heated to a higher temperature at which the main crystal phases separate.
  • This temperature is usually at least 20 ° C., preferably at least 50 ° C., above the formation temperature of the primary crystallites.
  • main crystal phases secondary crystals
  • further crystal phases such as, for example, pyrochlores, pyrosilicates, xenotimes and / or Rutile and mixtures thereof, to be separated from the residual glass phase remaining between the primary and / or secondary crystals.
  • the glass ceramic according to the invention shows a coefficient of thermal expansion (CTE) 020-600 of 4 - 9 x 10 ⁇ 6 K -1 (determined according to DIN-ISO 7991).
  • the glass according to the invention is particularly suitable for the production of magnetic storage disks, magneto-optical storage devices, mirror carriers or substrates therefor.
  • FIG. 1 shows the results of the differential thermal analysis of a glass according to the invention (so-called DTA curve of exemplary embodiment No. 1).
  • the turning point of the drop in the DTA curve to this minimum characterizes the transformation temperature of the glass Tg (in FIG. 1: approx. 780 ° C.).
  • the flat maximum in the marked temperature interval 1 reflects the temperature range of nucleation or the excretion of primary crystal phases.
  • the range of the elimination of nuclei which cannot be characterized by structural analysis or very small spinel crystallites (crystallite volume ⁇ 150 nm 3 ).
  • the marked temperature range 2 contains a clear peak. This indicates the exothermic crystallization reaction of secondary crystal phases on primary seeds.
  • a sharp dip in Fig. 1: approx. 1415 ° C, labeled Fp, indicates the melting point of the glass ceramic.
  • the nuclei or primary crystallites are preferably formed at a temperature of the lower two thirds of the temperature interval 1, it being preferred to choose a temperature within the lower half. A temperature in the lower third of this marked area 1 is even more preferred.
  • the mixture is heated to a higher temperature at which the main crystal phases of the glass ceramic separate or primary crystallites show considerable size growth.
  • a temperature is usually in the marked temperature interval 2 and at least 20 K, preferably at least 50 K above the nucleation temperature. tur, whereby a temperature range of + 50 K around the peak maximum in region 2 (marked in FIG. 1) is aimed for. The glass ceramic is left at this temperature until the precipitated crystallites have reached a sufficient size.
  • the material is then heated to a further higher temperature, usually from temperature intervals 3 and 4.
  • the glass ceramic is kept at this temperature in order to crystallize out the tertiary crystal phases with a sufficient crystallite size.
  • the holding times at the respective temperatures for the formation of primary, secondary or tertiary crystalline phases depend on their growth rate and are usually at least 15 minutes, preferably at least 30 minutes, with a holding time between 60 and 180 minutes, in particular between 90 and 120 minutes, being particularly preferred is.
  • the upper limit of the holding times is usually a maximum of 60 hours, preferably a maximum of 12 hours.
  • the heating up to a temperature just below Tg takes place relatively quickly, ie with 5-15 K min "1 , in particular with about 10 K min " 1 .
  • the temperature for the precipitation of primary crystal phases or nuclei is then heated more slowly, at about 3 to 8 K min "1 , usually at about 5 K min " 1 .
  • the heating rate can also be 0.5-3 K min "1.
  • the higher temperatures at which Crystallizing secondary or tertiary crystal phases can be achieved with very different heating rates in the range 0.5-200 K min "1. These heating rates are determined depending on the growth rates of the respective crystal phases in the respective matrix material.
  • the respective glass batch was melted in a Pt / Rh crucible at 1600-1700 ° C. in batches of 100 g to 3 kg and cast into plates (0.5-3 cm thick). These glass plates were slowly cooled to room temperature at temperatures Tg + 20 K.
  • the glasses were thermally treated according to the procedure given above, as indicated in the table below. Crystallites from the different crystal phases separated out. The crystallization was carried out in one-stage or multi-stage tempering programs. For example, the specification 800 ° C / 2h, 950 ° C / lh, 1050 ° C / lh means that the glass undergoes a thermal treatment at 800 ° C for 2 hours, then at 950 ° C for one hour and finally for 1 hour at 1050 ° C.
  • the glasses and glass ceramics shown were extensively characterized.
  • the modulus of elasticity and the bending strength were determined from bending tests, the K iC value was calculated by measuring radial crack lengths using the VICKERS method.
  • the density was determined by means of the buoyancy method and the coefficient of thermal expansion by means of dilatometric measurements.
  • the crystal phases were analyzed by means of X-ray diffractometry. Crystal structure and texture were derived from scanning electron microscope images. Atomic force microscopic examinations (AFM) are carried out according to standard polishing, which provide a surface topography. The averaging of the measured values leads to the specified values of the surface roughness.
  • Ra means the arithmetic mean and rq (or rms) the geometric mean of the measured values.
  • PV denotes the distance from peak to valley of the maxima / minima along a measurement section.

Abstract

The invention relates to crystallisable aluminosilicate magnesium-containing glass which is used for producing extremely solid and break-resistant glass-ceramics having an easily polished surface. The inventive crystallisable glass contains 5-33 mass % of SiO2, 25-40 mass % of Al2O3, 5-25 mass % of MgO, 0-15 mass % of B2O3, 0.1-30 mass % of Y2O3, Ln2O3, As2O3 and /or Nb2O5 and 0.1-10 mass % of P2O5.

Description

Kristallisierbares Glas und seine Verwendung zur Herstellung einer hochsteifen, bruchfesten Glaskeramik mit gut polierbarer Oberfläche Crystallizable glass and its use for the production of a highly rigid, break-resistant glass ceramic with a surface that is easy to polish
Die Erfindung betrifft ein hochsteifes, bruchfestes, kristallisierbares Glas vom magnesiumhaltigen Alumosilikattyp, eine daraus hergestellte Glaskeramik, die eine gut polierbare Oberfläche aufweist, sowie deren Verwendung in Magnet- Speicherplatten und Spiegelsystemen bzw. als Substrat dafür.The invention relates to a highly rigid, unbreakable, crystallizable glass of the magnesium-containing aluminosilicate type, a glass ceramic produced therefrom, which has a surface that can be polished well, and the use thereof in magnetic storage disks and mirror systems or as a substrate therefor.
An Magnetspeicherplatten und an magneto-optische Speichermaterialien sowie an rein optische Speichermaterialien und Spiegelmaterialien werden hohe Anforderungen bezüglich Bruchfestigkeit, hoher spezifischer Steifigkeit und hoher Oberflächengüte gestellt. Die wachsenden Anforderungen, die hinsichtlich Speicherdichte und Zugriffsgeschwindigkeit z.B. an Festplattenlaufwerke gestellt werden, erhöhen die mechanischen Belastungen, die auf die Substratmaterialien einwirken: Um die Zugriffszeit deutlich zu verringern, muss sowohl die Drehzahl der Speicherplatte auf mehr als 15 000 rpm erhöht und der Abstand von Lesekopf und Plattenoberfläche weiter abgesenkt werden. Um dies zu ermöglichen werden Trägermaterialien benötigt, die eine hohe Bruchfestigkeit (Klc und Biegebruchfestigkeit) und einen sehr hohen E-Modul bzw. eine sehr hohe spezifische Steifigkeit und damit eine geringe Flutteramplitude aufweisen. Darüber hinaus ist es absolut notwendig, dass das Material eine sehr geringe Oberflächenrauhigkeit von Ra < 0,5 nm bei einer Welligkeit von < 10 nm (ISO 1305 bzw. DIN 4768) aufweist. Außerdem muss bei der Herstellung einer magnetischen Beschichtung das Substratoder Trägermaterial thermischen Belastungen im Bereich von ca. 400 - 450°C widerstehen und aufgrund hoher Temperaturänderungen, wie sie zum Beispiel bei Sputterprozessen auftreten, beständig gegen Temperaturwechsel sein. Schließlich soll die thermische Ausdehnung der Speichermaterialien und Spiegel an die der Aufnahmevorrichtung (Spindel und Distanzstücke) angepasst werden. Diese werden zur Zeit aus Stahl gefertigt, so dass ein thermischer Ausdehnungskoeffizient von α20-3oo von ca. 12 ppm/K optimal ist, wobei jedoch auch kleinere Werte tolerierbar sind.Magnetic storage disks and magneto-optical storage materials as well as purely optical storage materials and mirror materials are subject to high demands in terms of breaking strength, high specific rigidity and high surface quality. The growing demands placed on storage density and access speed, for example on hard drives, increase the mechanical loads that act on the substrate materials: In order to significantly reduce the access time, the speed of the storage disk must be increased to more than 15,000 rpm and the distance from Read head and disk surface can be lowered further. In order to make this possible, support materials are required which have a high breaking strength (Klc and bending strength) and a very high modulus of elasticity or a very high specific stiffness and thus a low flutter amplitude. In addition, it is absolutely necessary that the material has a very low surface roughness of Ra <0.5 nm with a ripple of < 10 nm (ISO 1305 or DIN 4768). In addition, when producing a magnetic coating, the substrate or carrier material must have thermal loads in the range of withstand approx. 400 - 450 ° C and, due to high temperature changes, such as occur in sputtering processes, they are resistant to temperature changes. Finally, the thermal expansion of the storage materials and mirrors should be adapted to that of the receiving device (spindle and spacers). These are currently made of steel, so that a thermal expansion coefficient of α 20 - 3oo of approx. 12 ppm / K is optimal, although smaller values can also be tolerated.
Derzeit werden als Substrate für Magnetspeicherplatten Aluminiumlegierungen, Gläser und Glaskeramiken verwendet. Obwohl Gläser einen höheren E-Modul aufweisen, haben sie den Nachteil eines geringen Klc-Wertes. Dieser läßt sich durch thermisches oder chemisches Härten auch nur begrenzt verbessern.Aluminum alloys, glasses and glass ceramics are currently used as substrates for magnetic storage disks. Although glasses have a higher modulus of elasticity, they have the disadvantage of a low Klc value. This can only be improved to a limited extent by thermal or chemical hardening.
Glaskeramiken sind aufgrund ihres heterogenen Gefüges von in einer Glasmatrix eingebetteten Mikrokristallen weniger gut polierbar als Glas selbst oder Aluminium. Die geforderten Oberflächenrauhigkeiten von Ra < 0,5 nm werden daher von Glaskeramiken bislang selten erreicht. Ursache dafür sind oberflächennahe Kristallite, die im Allgemeinen härter sind als die sie umgebende Glasphase. Während der Polierschritte wird somit mehr Material vom Glas abgetragen als von den Kristalliten, wodurch eine rauhe Oberfläche entsteht. Für eine Vielzahl von Anwendungen sind solche Materialien daher nicht geeignet .Due to their heterogeneous structure of microcrystals embedded in a glass matrix, glass ceramics are less easy to polish than glass itself or aluminum. The required surface roughness of Ra <0.5 nm has therefore rarely been achieved by glass ceramics. This is due to near-surface crystallites, which are generally harder than the surrounding glass phase. During the polishing steps, more material is removed from the glass than from the crystallites, which creates a rough surface. Such materials are therefore unsuitable for a large number of applications.
Glaskeramiken, auch Vitrokeramiken genannt, sind polykristalline Festkörper, welche durch eine gezielte Entglasung, d.h. durch eine Kristallisation aus besonderen hierfür ge- eignenten Gläsern hergestellt werden. Diese Kristallisierung bzw. Keramisierung wird durch eine Erwärmung der Glaskörper oder gegebenenfalls auch durch Bestrahlen erreicht. Dabei enthalten die glaskeramischen Werkstoffe jedoch noch einen Restanteil an einer Glasphasenmatrix, in der die Kristalle eingelagert sind. Da sich Glaskeramiken in ihrer glasigen Vorstufe mit den üblichen glastechnischen Formgebungsverfahren zu jeder beliebigen Gestalt formen lassen und viele gewünschte Eigenschaften, wie Beständigkeit gegenüber Temperaturwechsel, geringen Ausdehnungskoeffizienten und gute elektrische Isolation, aufweisen, sind sie zur Herstellung von vielfältigen Gegenständen geeignet, wie beispielsweise von Kochfeldern, Geschirr, Hochspannungsisolatoren, Laborgegenständen, von Knochenersatz, oder auch zum Versiegeln umweltschädlicher Abfälle wie beispielsweise verbrannte Kernbrennstäbe.Glass ceramics, also called vitroceramics, are polycrystalline solids which are produced by targeted devitrification, ie by crystallization from special glasses suitable for this purpose. This crystallization or ceramization is achieved by heating the glass bodies or, if appropriate, also by irradiation. there However, the glass-ceramic materials still contain a residual portion of a glass phase matrix in which the crystals are embedded. Since glass ceramics in their glassy preliminary stage can be shaped into any shape using the usual glass-technical shaping processes and have many desired properties, such as resistance to temperature changes, low expansion coefficients and good electrical insulation, they are suitable for the production of a variety of objects, such as hobs , Dishes, high-voltage insulators, laboratory objects, bone replacements, or also for sealing environmentally harmful waste such as burnt nuclear fuel rods.
Ein gut untersuchtes System zur Ausbildung von Glas bzw. Glaskeramiken ist das DreistoffSystem Si02-Al203-MgO (MAS-System) . Innerhalb dieses DreistoffSystems existieren verschiedene Zusammensetzungsbereiche, in denen unterschiedlich spezifische kristalline Phasen existieren bzw. stabil sind oder sich ausbilden. Bislang beschränkten sich die Beschreibungen von Glaskeramiken in der Literatur auf diejenigen Bereiche des MAS-Systems, in denen die Kristallphasen Quarz (Si02) , Tridymit (Si02) , Enstatit (MgO-Si02), Cordierit (2 MgO-2 Al203-5 Si02) , Forsterit (MgO-Si02), Mullit (3 Al203-2 Si02) sowie gegebenenfalls Spinell (MgO-Al203) als die jeweils thermodynamisch stabilsten Phasen auftreten und somit auch als Hauptkristallphase ausgeschrieben werden konnten.A well-studied system for the formation of glass or glass ceramics is the three-substance system Si0 2 -Al 2 0 3 -MgO (MAS system). Within this three-substance system there are various compositional areas in which differently specific crystalline phases exist or are stable or develop. So far, the descriptions of glass ceramics in the literature have been limited to those areas of the MAS system in which the crystal phases quartz (Si0 2 ), tridymite (Si0 2 ), enstatite (MgO-Si0 2 ), cordierite (2 MgO-2 Al 2 0 3 -5 Si0 2 ), forsterite (MgO-Si0 2 ), mullite (3 Al 2 0 3 -2 Si0 2 ) and optionally spinel (MgO-Al 2 0 3 ) occur as the most thermodynamically stable phases and thus also as Main crystal phase could be advertised.
Der relativ eng umrissene Bereich, in dem stabile Gläser bekannt sind, ist bereits vielfach in der Literatur beschrieben, wie beispielsweise in P.W. McMillen: "Glass Ceramics", Academic Press, London, NY, San Francisco, 2. Ausgabe (1979), Seite 18 ff. Darin ist auch beschrieben, dass für die Umwandlung von Gläsern des MAS-Systems in Glaskeramiken Ti02, Zr02 sowie P205 als Keimbildner in Frage kommen.The relatively narrow range in which stable glasses are known has already been described many times in the literature, for example in PW McMillen: "Glass Ceramics", Academic Press, London, NY, San Francisco, 2nd Edition (1979), page 18 ff. It also describes that for the conversion of glasses of the MAS system into glass ceramics Ti0 2 , Zr0 2 and P 2 0 5 can be considered as nucleating agents.
In der US-A-2, 920, 971 (Stookey et al . ) sind Alumosilikatglä- ser beschrieben, die Titanoxid und Magnesiumoxid enthalten. Dabei wird durch eine thermische Nachbehandlung als kristalline Magnesium-Aluminium-Silikat-Phase Cordierit ausgeschieden.US Pat. No. 2,920,971 (Stookey et al.) Describes aluminosilicate glasses which contain titanium oxide and magnesium oxide. A thermal post-treatment eliminates cordierite as a crystalline magnesium-aluminum-silicate phase.
In der EP-A-0 289 903 wird ein glas-/keramikbeschichtetes Substrat beschrieben, welches eine Zusammensetzung des oben genannten DreistoffSystems mit einem 42 - 68 %igen Gewichtsanteil an Si02 enthält.EP-A-0 289 903 describes a glass / ceramic-coated substrate which contains a composition of the above-mentioned three-substance system with a 42-68% weight fraction of SiO 2 .
JA-91045027 B (Nishigaki, J. et al . ) , JA-91131546 A (Tanabe, N. et al.), JA-92106806 A (Okubo, F. et al . ) EP 55 237 7 (Kawamura et al . ) beschreiben unterschiedliche glas- bzw. glaskeramische Zusammensetzungen. Diese Zusammensetzungen enthalten jedoch keine kristallinen Magnesium-Aluminium-Silikat-Phasen oder einen geringeren Si02-Anteil als 33 Gew.-%.JA-91045027 B (Nishigaki, J. et al.), JA-91131546 A (Tanabe, N. et al.), JA-92106806 A (Okubo, F. et al.) EP 55 237 7 (Kawamura et al. ) describe different glass or glass ceramic compositions. However, these compositions contain no crystalline magnesium-aluminum-silicate phases or a lower SiO 2 content than 33% by weight.
In der EP-A-1 067 101, der EP-A-1 067 102 und der EP-A- 0 941 973 werden Yttrium-haltige MAS-Glaskeramiken als Substrate für Speichermedien beschrieben. Darin wird festgestellt, dass die Zugabe von 0,8 - 10 Mol-% Yttriumoxid zu einem Grundglasgemenge bestehend aus 35-65 Mol-% Si02, 5-25 Mol-% A1203, 10-40 Mol-% MgO und 5-12 Mol-% Ti02 dazu führt, dass dieses Glas leichter geschmolzen werden kann, gute mechanische Eigenschaften aufweist und nach einer thermischen Behandlung die entstandene Glaskeramik ein E-Modul von > 130 GPa aufweist. Diese Keramiken enthalten als Kristallphasen Hochquarzmischkristalle mit wechselnden Zusammensetzungen, z.B. MgO:Al203:Si02 = 2:2:5; 1:1:3; 1:1:4 bzw. Mischungen, sowie Enstatit (MgO-Al203 bzw. MgO-0,5 Al203-Si02). Als Keimbildner dient Ti02, das weiterhin den Verlust an Glastrans- parenz in gewissen Grenzen kompensiert. Y203 dient als Zusatz, um die Verarbeitungstemperatur zu senken. Ein Y203-Ge- halt von > 10 Mol-% ist dabei jedoch unerwünscht, weil er die Kristallisationsneigung des Glases zu sehr erhöht.EP-A-1 067 101, EP-A-1 067 102 and EP-A-0 941 973 describe yttrium-containing MAS glass ceramics as substrates for storage media. It states that the addition of 0.8-10 mol% yttrium oxide to a basic glass batch consisting of 35-65 mol% Si0 2 , 5-25 mol% A1 2 0 3 , 10-40 mol% MgO and 5-12 mol% Ti0 2 means that this glass can be melted more easily, has good mechanical properties and, after thermal treatment, the resulting glass ceramic has a modulus of elasticity of> 130 GPa. These ceramics contain high quartz mixed crystals with changing compositions, for example MgO: Al 2 0 3 : Si0 2 = 2: 2: 5; 1: 1: 3; 1: 1: 4 or mixtures, as well as enstatite (MgO-Al 2 0 3 or MgO-0.5 Al 2 0 3 -Si0 2 ). The nucleating agent used is Ti0 2 , which continues to reduce the loss of glass parenz compensated within certain limits. Y 2 0 3 serves as an additive to lower the processing temperature. However, a Y 2 0 3 content of> 10 mol% is undesirable because it increases the tendency of the glass to crystallize too much.
Die bislang üblichen Glaskeramiken enthalten als Hauptkristallphasen üblicherweise Enstatit, Forsterit und Cordierit . Als Nebenphasen werden auch Spinell- und Sapphirinphasen beschrieben. Dabei liegt die Untergrenze des Si02-Gehaltes bei 35 Gew.-%, wobei Si02-Untergrenzen von 40 bzw. 42-44 Gew.-% üblich sind. Bislang wurde davon ausgegangen, dass unterhalb dieser Si02-Konzentration keine technologisch verarbeitbaren Gläser herstellbar sind.The usual glass ceramics usually contain enstatite, forsterite and cordierite as the main crystal phases. Spinel and sapphirine phases are also described as secondary phases. The lower limit of the Si0 2 content is 35% by weight, with Si0 2 lower limits of 40 or 42-44% by weight being common. So far it has been assumed that below this Si0 2 concentration no technologically processable glasses can be produced.
In der JP-A-2000-327365 werden als Untergrenze für alkali- haltige Gläser 25 Gew.-% Si02 und in der JP-A-11079785 für alkalifreie Gläser 30 Gew.-% beschrieben.JP-A-2000-327365 describes 25% by weight Si0 2 as the lower limit for alkali-containing glasses and 30% by weight in JP-A-11079785 for alkali-free glasses.
Die Erfindung hat zum Ziel, neue Gläser bereitzustellen, die einen geringen Si02-Gehalt haben, dabei dennoch glastechnologisch verarbeitbar sind und die sich in Glaskeramiken umwandeln lassen, die einen hohen E-Modul aufweisen.The aim of the invention is to provide new glasses which have a low SiO 2 content but which can nevertheless be processed using glass technology and which can be converted into glass ceramics which have a high modulus of elasticity.
Die Erfindung hat weiterhin zum Ziel, eine derartige Glaskeramik bereitzustellen, die auf die gewünschte Oberflächenrauhigkeit polierbar ist und die als Substrat für Magnetspeicherplatten oder Spiegelsysteme verwendbar ist.Another object of the invention is to provide such a glass ceramic which can be polished to the desired surface roughness and which can be used as a substrate for magnetic storage disks or mirror systems.
Dieses Ziel wird durch das in den Ansprüchen definierte Glas sowie der daraus erhältlichen Glaskeramik und deren Verwendung erreicht .This goal is achieved by the glass defined in the claims and the glass ceramics obtainable therefrom and their use.
Überraschenderweise wurde gefunden, dass Gläser und Glaskeramiken herstellbar sind, welche einen geringen Anteil an netzwerkbildenden Si02 unterhalb des zuvor angegebenen Bereiches von > 30 Gew.-% enthalten und die sich auch für die technische Verarbeitung eignen, wenn diesem Glas Y203/ Nb205 und/oder Ln203 zugesetzt wird. Dabei wurde auch überraschenderweise gefunden, dass ein derartiges Glas nicht nur hochsteif und bruchfest ist, sondern auch vor der gezielten Keimbildung bzw. Keramisierung gegenüber der Ausbildung kristalliner Phasen stabil, also zur Entspannung kühlbar ist. Eine derartige Glaskeramik ist außerdem auf die gewünschte Oberflächenrauhigkeit von Ra < 0,5 nm polierbar.Surprisingly, it was found that glasses and glass ceramics can be produced which contain a small proportion of network-forming SiO 2 below the previously specified range of> 30% by weight and which are also suitable for Technical processing is suitable if Y 2 0 3 / Nb 2 0 5 and / or Ln 2 0 3 is added to this glass. It was also surprisingly found that such a glass is not only highly rigid and unbreakable, but also stable against the formation of crystalline phases prior to the targeted nucleation or ceramization, that is to say it can be cooled to relax. Such a glass ceramic can also be polished to the desired surface roughness of Ra <0.5 nm.
Das erfindungsgemäße Glas bzw. die daraus erhaltene Glaskeramik wird aus dem DreistoffSystem "Si02-MgO-Al203" gebildet und enthält zusätzlich einen Anteil an B203. Dabei beträgt die Mindestmenge an Si02 5 Gew.-%, insbesondere 10 Gew.-%, wobei 15 Gew.-% besonders bevorzugt sind. Die Obergrenze beträgt üblicherweise 33 Gew.-% bzw. 30 Gew. -%, wobei 28 Gew.- % und insbesondere 25 Gew.-% bevorzugt sind.The glass according to the invention or the glass ceramic obtained therefrom is formed from the three-substance system "Si0 2 -MgO-Al 2 0 3 " and additionally contains a proportion of B 2 0 3 . The minimum amount of SiO 2 is 5% by weight, in particular 10% by weight, with 15% by weight being particularly preferred. The upper limit is usually 33% by weight or 30% by weight, with 28% by weight and in particular 25% by weight being preferred.
Die Mindestmenge an MgO beträgt 5 Gew.-%, vorzugsweise 8 Gew.-%, wobei 10 Gew.-% besonders bevorzugt sind. Die Obergrenze von MgO liegt bei 25 Gew.-%, wobei 20 Gew.-% bevorzugt sind. Der Gehalt an A1203 beträgt mindestens 25 Gew.-%, vorzugsweise mindestens 30 Gew.-%. Der maximale Gehalt an Al203 beträgt 40 Gew.-% und vorzugsweise 38 Gew.-%. Boroxid muss nicht notwendigerweise vorhanden sein, jedoch beträgt der Gehalt an B203 vielfach mindestens 1 Gew.-%, üblicherweise mindestens 2 Gew.-% und vorzugsweise mindestens 3 Gew.-% und die Obergrenze von B203 liegt in der erfindungsgemäßen Zusammensetzung bei maximal 15 Gew.-%, üblicherweise bei maximal 12 Gew.-% und vorzugsweise bei maximal 10 bzw. maximal 9 Gew.-%.The minimum amount of MgO is 5% by weight, preferably 8% by weight, 10% by weight being particularly preferred. The upper limit of MgO is 25% by weight, with 20% by weight being preferred. The A1 2 0 3 content is at least 25% by weight, preferably at least 30% by weight. The maximum Al 2 0 3 content is 40% by weight and preferably 38% by weight. Boron oxide does not necessarily have to be present, but the content of B 2 0 3 is often at least 1% by weight, usually at least 2% by weight and preferably at least 3% by weight, and the upper limit of B 2 0 3 is that The composition according to the invention at a maximum of 15% by weight, usually at a maximum of 12% by weight and preferably at a maximum of 10 or at most 9% by weight.
Die Oxide der Gruppe Y203, Ln203 und Nb203 betragen in der erfindungsgemäßen Zusammensetzung mindestens 0,1 Gew.-%, üblicherweise mindestens 3 Gew.-% und vorzugsweise mindestens 12 Gew.-%. Die Obergrenze dieser Oxide beträgt 30 Gew.-%, vorzugsweise 28 Gew.-%, wobei eine Obergrenze von 25 Gew.-% besonders bevorzugt ist. Dabei betragen die Mengen der einzelnen Oxide üblicherweise 0,1-30 Gew.-%, vorzugsweise 10-30 Gew.-% für Y203 und 0-20 Gew.-% bzw. 0-20 Gew.-% für Ln203. Ln umfasst dabei die Lanthanoiden, insbesondere La, Ce, Pr, Nd, Eu, Yb, Ho und Er. Die erfindungsgemäße Zusammensetzung kann als weitere Komponenten übliche Läuterungs- und Fluss- mittel, wie Sb203, As203, Sn02, in den für diese Zwecke üblichen Anteilen enthalten. Dabei beträgt ihre Obergrenze vorzugsweise jeweils für Sb203 bzw. As203 max. 5 % und vorzugsweise max. 2 %.The oxides of the group Y 2 0 3 , Ln 2 0 3 and Nb 2 0 3 in the composition according to the invention are at least 0.1% by weight, usually at least 3% by weight and preferably at least 12% by weight. The upper limit of these oxides is 30% by weight, preferably 28% by weight, an upper limit of 25% by weight is particularly preferred. The amounts of the individual oxides are usually 0.1-30% by weight, preferably 10-30% by weight for Y 2 O 3 and 0-20% by weight or 0-20% by weight for Ln 2 0 3 . Ln includes the lanthanoids, in particular La, Ce, Pr, Nd, Eu, Yb, Ho and Er. The composition according to the invention can contain, as further components, customary refining and fluxing agents, such as Sb 2 0 3 , As 2 0 3 , Sn0 2 , in the proportions customary for these purposes. Her upper limit is preferably max for Sb 2 0 3 or As 2 0 3 . 5% and preferably max. 2%.
In einer bevorzugten Ausführungsform enthält das erfindungs- gemäße Glas bzw. die Glaskeramik 0 - 12 Gew.-% Ti02, 0 - 10 Gew.-% Zr02, 0 - 5 Gew.-% CaO, 0 - 5 Gew.-% SrO, 0 - 5 Gew.- % BaO, 0 - 20 Gew.-% ZnO. In einer erfindungsgemäß bevorzugten Ausführungsform enthält die Zusammensetzung mindestens 2 Gew.-%, vorzugsweise mindestens 4 Gew.-% Ti02 und eine maximale Menge von vorzugsweise höchstens 12 Gew.-% und insbesondere höchstens 10 Gew.-%. Sofern diese überhaupt enthalten sind, beträgt die Mindestmenge für die übrigen genannten Oxide Zr02 und ZnO üblicherweise jeweils 1 oder 2 Gew.-% und die Höchstmenge jeweils 5 oder 8 Gew.-%.12 wt .-% Ti0 2, 0 - - 10 wt .-% Zr0 2, 0 - 5 wt .-% CaO, 0 - In a preferred embodiment of invention the proper glass or the glass ceramics containing 0 5 wt .-% SrO, 0-5% by weight BaO, 0-20% by weight ZnO. In a preferred embodiment according to the invention, the composition contains at least 2% by weight, preferably at least 4% by weight of TiO 2 and a maximum amount of preferably at most 12% by weight and in particular at most 10% by weight. If these are contained at all, the minimum amount for the other mentioned oxides Zr0 2 and ZnO is usually 1 or 2% by weight and the maximum amount is 5 or 8% by weight.
Das erfindungsgemäße Glas oder die erfindungsgemäße Glaskeramik ist vorzugsweise im wesentlichen frei von Alkalioxiden wie Li20, Na20 und K20 und enthält diese nur als mit den restlichen Gemengekomponenten eingeschleppte Verunreinigungen. Dabei bedeutet "im wesentlichen alkalifrei" eine Menge von höchstens 2 Gew.-%, wobei höchstens 0,5 Gew.-% üblich sind.The glass according to the invention or the glass ceramic according to the invention is preferably essentially free of alkali oxides such as Li 2 0, Na 2 0 and K 2 0 and contains these only as impurities introduced with the remaining batch components. "Essentially alkali-free" means an amount of at most 2% by weight, with at most 0.5% by weight being customary.
Es hat sich gezeigt, dass das erfindungsgemäße Glas bzw. die Glaskeramik bis zu 10 Gew.-%, üblicherweise < 5 Gew.-% an Übergangsmetalloxiden aufweisen kann, ohne dass sich dabei resultierende Eigenschaften, wie Steifigkeit, Bruchfestigkeit und Kristallisationsverhalten signifikant ändern. Übli- ehe, im erfindungsgemäßen Glas bzw. in der Glaskeramik enthaltene Übergangsmetalloxide umfassen die Oxide der Elemente Fe, Co, Ni, Cr, Mn, Mo, V, Pt, Pd, Rh, Ru und W und sind insbesondere Mn02, Fe203, NiO, CoO, Cr203, V205, M0O3 und/oder W03.It has been shown that the glass or glass ceramic according to the invention can contain up to 10% by weight, usually <5% by weight, of transition metal oxides without the resulting properties, such as rigidity, breaking strength and crystallization behavior, changing significantly. customary Before transition metal oxides contained in the glass according to the invention or in the glass ceramic comprise the oxides of the elements Fe, Co, Ni, Cr, Mn, Mo, V, Pt, Pd, Rh, Ru and W and are in particular Mn0 2 , Fe 2 0 3 , NiO, CoO, Cr 2 0 3 , V 2 0 5 , M0O 3 and / or W0 3 .
In einer erfindungsgemäß bevorzugten Ausführungsform beträgt die Summe der Komponenten SrO, BaO und CaO mindestens 1 Gew.-%, vorzugsweise mindestens 2 Gew.-% und üblicherweise höchstens 5 Gew.-% und insbesondere höchstens 4 Gew.-%. Sofern vorhanden, beträgt der Anteil der Oxide Ti02 und Zr02 in einer erfindungsgemäß bevorzugten Ausführungsform mindestens 1 Gew.-%, vorzugsweise mindestens 2 Gew.-% und vorzugsweise höchstens 13 Gew.-%, insbesondere höchstens 10 Gew.-%.In a preferred embodiment according to the invention, the sum of the components SrO, BaO and CaO is at least 1% by weight, preferably at least 2% by weight and usually at most 5% by weight and in particular at most 4% by weight. If present, the proportion of the oxides Ti0 2 and Zr0 2 in an embodiment preferred according to the invention is at least 1% by weight, preferably at least 2% by weight and preferably at most 13% by weight, in particular at most 10% by weight.
Das erfindungsgemäße Glas bzw. die erfindungsgemäße Glaskeramik weist einen hohen Elastizitätsmodul von mindestens > 110 GPa auf. Üblicherweise liegt der E-Modul oberhalb 120 Gpa. In Abhängigkeit vom Keramisierungsprogramm sind Glaskeramiken mit E-Moduli oberhalb 150 Gpa, in einigen Fällen sogar > 200 Gpa, darstellbar. (Bestimmung des E-Moduls nach DIN EN 843-2, Punkt 4, Verfahren A: statisches Biegeverfahren) .The glass according to the invention or the glass ceramic according to the invention has a high modulus of elasticity of at least> 110 GPa. The modulus of elasticity is usually above 120 Gpa. Depending on the ceramization program, glass ceramics with E-moduli above 150 Gpa, in some cases even> 200 Gpa, can be produced. (Determination of the modulus of elasticity according to DIN EN 843-2, point 4, method A: static bending method).
In der erfindungsgemäßen Glaskeramik sind die Kristallite in einer glasigen Matrix eingelagert und weisen üblicher-, aber nicht notwendigerweise, eine Größe von < 100 nm bis ca. 3 μm auf. Für eine gute Polierbarkeit der Glaskeramiken sind Kri- stallitgrößen im Bereich 50-500 nm besonders bevorzugt. Es wurde gefunden, dass aus einer erfindungsgemäßen Glaszusammensetzung durch Kristallisation eine Glaskeramik erhalten wird, die als Hauptkristallphasen Spinell, Sapphirin und/oder Cordierit enthält. Dabei wurde nämlich überraschenderweise auch gefunden, dass die gewünschten Eigenschaften der Glaskeramik gerade dann erhalten werden, wenn die üblicherweise mit hohen E-Moduli in Verbindung gebrachten Kris- tallphasen Enstatit, Hoch- oder Tiefquarz sowie Hochquarz- mischkristalle vermieden werden, was insbesondere mit der erfindungsgemäßen Zusammensetzung möglich ist. Weiterhin können die erfindungsgemäß erhaltenen Glaskeramiken Kristalle mit einer Pyrochlorstruktur A2B207 aufweisen, worin A3+ ein Lantanoid und/oder Yttrium und B4+ Zr, Ti, Sn, und/oder Ru bedeuten. Darüber hinaus können sie Pyrosilikate der allgemeinen Formel A2Si207, worin A3+ ein Lantanoid, Y und/ oder Sc bedeutet, enthalten. Vorzugsweise sind dies jedoch Y2Si207 (Yttriumpyrosilikat, Yttrialit) bzw. Y2Ti207 (Yttropyro- chlor) .In the glass ceramic according to the invention, the crystallites are embedded in a glassy matrix and more usually, but not necessarily, have a size of <100 nm to approximately 3 μm. For good polishability of the glass ceramics, crystallite sizes in the range of 50-500 nm are particularly preferred. It has been found that a glass ceramic is obtained from a glass composition according to the invention by crystallization and contains spinel, sapphirine and / or cordierite as the main crystal phases. Surprisingly, it was also found that the desired properties of the glass ceramic are obtained when the crystals usually associated with high moduli of elasticity are obtained. tall phase entstatite, high or deep quartz and high quartz mixed crystals can be avoided, which is possible in particular with the composition according to the invention. Furthermore, the glass ceramics obtained according to the invention can have crystals with a pyrochlore structure A 2 B 2 0 7 , in which A 3+ is a lantanoid and / or yttrium and B 4+ is Zr, Ti, Sn, and / or Ru. In addition, they can contain pyrosilicates of the general formula A 2 Si 2 0 7 , in which A 3+ is a lantanoid, Y and / or Sc. However, these are preferably Y 2 Si 2 0 7 (yttrium pyrosilicate, yttrialite) or Y 2 Ti 2 0 7 (yttropyrochloro).
Es wurde erfindungsgemäß auch gefunden, dass die Reihenfolge der Ausscheidung der Kristallphasen einen entscheidenden Einfluss auf den E-Modul ausübt. Dabei hat es sich gezeigt, dass nach der Primärausscheidung kleiner Spinellkristallite sowie gegebenenfalls kleiner Sapphirinkristallite, insbesondere solcher vom Typ Mg2Al4SiOι0, die nachfolgende sekundäre Kristallphasen vom Sapphirin- und Cordierittyp um die Pri- märkristallite herum erfolgt, insbesondere wie ein Überzug über die Primärkristallite. Erfindungsgemäß wurde gefunden dass der Si0 -Gehalt und die Kristallstruktur der sekundär ausgeschiedenen Phase abhängig vom Silizium- und Yttriumgehalt des Grundglases sind, wobei ein niedriger Si02-Gehalt des Grundglases die Bildung von Sapphirin fördert. Durch Auswahl und Gehalt der Keimbildner (Ti02, Zr02, P205) ist die Kristallitgröße der Primärkristalle oder der Keime gezielt steuerbar. Die Größe der Kristallite der sekundären Phasen kann kinetisch oder thermodynamisch kontrolliert werden (Ausnutzung von Diffusions- und Epitaxiephänomenen) . Als tertiäre Kristallphasen sind Pyrochlore, Pyrosilikate, Xeno- ti e und/oder Rutil enthalten. Über deren Ausscheidung kann der Restglasphasenanteil und damit auch der E-Modul der resultierenden Glaskeramik beeinflusst werden. Erfindungsgemäß wurde auch gefunden, dass Ti02 in der erfindungsgemäßen Glaskeramik nicht allein als Keimbildner fungiert, sondern auch in die Kristallphasen mit hohem E-Modul eingebaut wird. Überraschenderweise ist auch gefunden worden, dass Läutermittelzugaben wie Sn02 und As203 bei der erfindungsgemäßen Vorgehensweise in Spinell- bzw. Pyrochlorphasen eingebunden werden. Auf diese Weise lassen sich erfindungsgemäß der Restglasphasenanteil noch weiter reduzieren und gleichzeitig Kristallite mit hohem E-Modul gezielt ausscheiden.It has also been found according to the invention that the order in which the crystal phases are precipitated has a decisive influence on the modulus of elasticity. It has been shown that after the primary separation of small spinel crystallites and possibly small sapphirin crystallites, in particular those of the Mg 2 Al 4 SiOι 0 type , the subsequent secondary crystal phases of the sapphirin and cordierite type take place around the primary crystallites, in particular like a coating the primary crystallites. According to the invention, it was found that the SiO 2 content and the crystal structure of the secondary phase are dependent on the silicon and yttrium content of the base glass, a low SiO 2 content of the base glass promoting the formation of sapphirine. The crystallite size of the primary crystals or the nuclei can be controlled in a targeted manner by the selection and content of the nucleating agents (Ti0 2 , Zr0 2 , P 2 0 5 ). The size of the crystallites of the secondary phases can be controlled kinetically or thermodynamically (exploitation of diffusion and epitaxial phenomena). Pyrochlores, pyrosilicates, xenotites and / or rutile are contained as tertiary crystal phases. The residual glass phase fraction and thus also the modulus of elasticity of the resulting glass ceramic can be influenced by their elimination. According to the invention, it was also found that Ti0 2 in the invention Glass ceramics not only act as nucleating agents, but are also incorporated into the crystal phases with a high modulus of elasticity. Surprisingly, it has also been found that refining agents such as Sn0 2 and As 2 0 3 are incorporated into spinel or pyrochlore phases in the procedure according to the invention. In this way, according to the invention, the residual glass phase fraction can be reduced even further and, at the same time, crystallites with a high modulus of elasticity can be eliminated in a targeted manner.
Da die dargestellten Schmelzen praktisch alkalifrei sind, ist auch die Korrosion von der auf das Speichersubstrat aufgebrachten magnetischen bzw. magneto-optischen bzw. optischen Schicht in Folge von Alkalidiffusion nicht möglich.Since the melts shown are practically alkali-free, the corrosion of the magnetic or magneto-optical or optical layer applied to the storage substrate as a result of alkali diffusion is also not possible.
Erfindungsgemäß wurde auch gefunden, dass sich mit dem erindungsgemäßen Glas während der Keramisierung an der Oberfläche des Glaskeramikkδrpers eine glasige Schicht ausbildet, deren Dicke deutlich größere Ausmaße aufweist als die zwischen den Kristalliten verbleibende Restglasmenge. Diese glasige Schicht bewirkt, dass Halbzeuge für Speichersubstrate eine sehr geringe Oberflächenrauhigkeit aufweisen. Da diese Glasphase besser polierbar ist als die ausgeschiedenen Kristalle, reduziert sich der Nachbearbeitungsaufwand erheblich.It has also been found according to the invention that a glassy layer is formed with the glass according to the invention during the ceramization on the surface of the glass ceramic body, the thickness of which is significantly greater than the amount of residual glass remaining between the crystallites. This glassy layer means that semi-finished products for storage substrates have a very low surface roughness. Since this glass phase is easier to polish than the deposited crystals, the post-processing effort is reduced considerably.
Das erfindungsgemäße Glas bzw. die erfindungsgemäße Glaskeramik weist außerdem sehr gute mechanische Eigenschaften, wie eine hohe Biegebruchfestigkeit (bestimmt als 3 -Punkt- Biegefestigkeit nach DIN EN 843-1) von > 150 MPa, insbesondere > 180 MPa und einem K1C (bestimmt nach A.G. Evans, E.A. Charles, J. Amer. Ceram. Soc. 59 (1976) 371) von > 1,3 MPam1/2, auf .The glass according to the invention or the glass ceramic according to the invention also has very good mechanical properties, such as a high flexural strength (determined as a 3-point flexural strength according to DIN EN 843-1) of > 150 MPa, in particular> 180 MPa and a K 1C (determined according to AG Evans, EA Charles, J. Amer. Ceram. Soc. 59 (1976) 371) of> 1.3 MPam 1/2 .
Die erfindungsgemäßen Gläser werden durch eine thermische Behandlung bei Temperaturen oberhalb Tg in die entsprechende Glaskeramik überführt. Dabei wird die Umwandlungstemperatur und die Ausbildung von Kristallphasen mittels an sich bekannter Methoden, wie z.B. durch eine mittels Differential- thermoanalyse (DTA) ermittelte Haltekurve, bestimmt.The glasses according to the invention are converted into the corresponding glass ceramic by thermal treatment at temperatures above Tg. The transition temperature and the formation of crystal phases is determined by methods known per se, such as, for example, by means of a holding curve determined by means of differential thermal analysis (DTA).
Zur Umwandlung des Glases in eine Glaskeramik wird so lange auf die Umwandlungstemperatur erwärmt, bis kristalline Phasen ausgeschieden werden. Die Gläser werden üblicherweise bei einer Temperatur von ca. 5 - 50°C oberhalb Tg, vorzugsweise 10 - 30°C oberhalb Tg solange erwärmt bis sich ausreichend primäre Kristallite gebildet haben. Die übliche Glasübergangstemperatur dieser Gläser beträgt 700 - 850°C.To convert the glass into a glass ceramic, heat to the transition temperature until crystalline phases are separated. The glasses are usually heated at a temperature of about 5-50 ° C. above Tg, preferably 10-30 ° C. above Tg, until sufficient primary crystallites have formed. The usual glass transition temperature of these glasses is 700 - 850 ° C.
Die Haltedauer zur Ausbildung der Primärkristallite bzw. Kristallkeime hängt von den gewünschten Eigenschaften ab und beträgt üblicherweise mindestens 0,5 Stunden, vorzugsweise mindestens 1 Stunde, wobei mindestens 1,5 Stunden besonders bevorzugt sind. Als maximale Dauer werden üblicherweise 3 Tage angesehen, wobei 2 Tage und insbesondere 1 Tag als maximale Dauer zur Ausbildung der Primärkristallkeime bevorzugt sind. In den meisten Fällen ist eine Dauer von 2-12 Stunden ausreichend. Anschliessend wird auf eine höhere Temperatur erwärmt, bei der sich die Hauptkristallphasen abscheiden.The holding time for the formation of the primary crystallites or crystal nuclei depends on the desired properties and is usually at least 0.5 hours, preferably at least 1 hour, with at least 1.5 hours being particularly preferred. The maximum duration is usually considered to be 3 days, with 2 days and in particular 1 day being preferred as the maximum duration for the formation of the primary crystal nuclei. In most cases, a duration of 2-12 hours is sufficient. The mixture is then heated to a higher temperature at which the main crystal phases separate.
Diese Temperatur liegt üblicherweise mindestens 20°C , vorzugsweise mindestens 50°C, oberhalb der Bildungstemperatur der Primärkristallite. In besonderen Fällen hat es sich als zweckmässig erwiesen, nach Ausscheidung der Hauptkristallphasen (Sekundärkristalle) , insbesondere Spinell, Sapphirin und/oder Cordierit, noch einmal auf weitere höhere Temperaturen zu erwärmen und so weitere Kristallphasen, wie z.B. Pyrochlore, Pyrosilikate, Xenotime und/ oder Rutil sowie Mischungen davon, aus der zwischen den Primär- und/oder Sekundärkristallen verbliebenen Restglasphase auszuscheiden. Die erfindungsgemäße Glaskeramik zeigt einen Wärmeausdehnungskoeffizienten (WAK) 020-600 von 4 - 9 x 10~6K-1 (bestimmt nach DIN-ISO 7991) .This temperature is usually at least 20 ° C., preferably at least 50 ° C., above the formation temperature of the primary crystallites. In special cases, it has proven to be expedient, after the main crystal phases (secondary crystals), in particular spinel, sapphirin and / or cordierite, to be excreted again to further higher temperatures, and so further crystal phases, such as, for example, pyrochlores, pyrosilicates, xenotimes and / or Rutile and mixtures thereof, to be separated from the residual glass phase remaining between the primary and / or secondary crystals. The glass ceramic according to the invention shows a coefficient of thermal expansion (CTE) 020-600 of 4 - 9 x 10 ~ 6 K -1 (determined according to DIN-ISO 7991).
Das erfindungsgemäße Glas ist besonders zur Herstellung von Magnetspeicherplatten, magneto-optischen Speichern, Spiegelträgern bzw. Substraten hierfür geeignet.The glass according to the invention is particularly suitable for the production of magnetic storage disks, magneto-optical storage devices, mirror carriers or substrates therefor.
Die Erfindung soll an den folgenden Beispielen näher erläutert werden.The invention is illustrated by the following examples.
Figur 1 gibt die Ergebnisse der differenzialthermoanalyti- schen Untersuchung eines erfindungsgemäßen Glases wider (sog. DTA-Kurve des Ausführungs-Beispiels Nr. 1) .FIG. 1 shows the results of the differential thermal analysis of a glass according to the invention (so-called DTA curve of exemplary embodiment No. 1).
Zur Festlegung des Temperatur- eit-Programmes zur erfindungsgemäßen Überführung des Grundglases in eine Glaskeramik werden die Ausbildungstemperaturen der einzelnen Kristall- phasen abgeschätzt. Dies erfolgt mit Hilfe der Differenzial- thermoanalyse . In deren Ergebnis erhält man Kurven (s.v.w. Fig. 1) in denen sich exotherme Reaktionen als Peak (Maximum) bzw. endotherme Reaktionen als Dip (Minimum) bezüglich einer Kurvennormalen (Strich-Punkt-Linie) äußern. Kristallisationsreaktionen verlaufen im allgemeinen exotherm; Gefügeoder Aggregatszustandsänderungen üblicherweise endotherm.In order to determine the temperature / time program for converting the basic glass into a glass ceramic according to the invention, the formation temperatures of the individual crystal phases are estimated. This is done with the help of differential thermal analysis. In the result, one obtains curves (see Fig. 1) in which exothermic reactions are expressed as peaks (maximum) or endothermic reactions as dip (minimum) with respect to a curve normal (dash-dot line). Crystallization reactions are generally exothermic; Structural or aggregate state changes are usually endothermic.
Für die erfindungsgemäßen Gläser wird ein erstes Minimum im Temperaturbereich > 700°C, häufig auch oberhalb 740°C, erreicht. Der Wendepunkt des Abfalles der DTA-Kurve zu diesem Minimum kennzeichnet die Transformationstemperatur des Glases Tg (in Fig. 1: ca. 780°C) .A first minimum in the temperature range> 700 ° C., often also above 740 ° C., is reached for the glasses according to the invention. The turning point of the drop in the DTA curve to this minimum characterizes the transformation temperature of the glass Tg (in FIG. 1: approx. 780 ° C.).
Das flache Maximum im markierten Temperaturintervall 1 widerspiegelt den Temperaturbereich der Keimbildung bzw. der Ausscheidung primärer Kristallphasen. Im Falle der erfindungsgemäßen Gläser/Glaskeramiken erfolgt in diesem Tempera- turbereich die Ausscheidung kristallstrukturanalytisch nicht näher charakterisierbarer Keime bzw. sehr kleiner Spinell- kristallite (Kristallitvolumen < 150 nm3) .The flat maximum in the marked temperature interval 1 reflects the temperature range of nucleation or the excretion of primary crystal phases. In the case of the glasses / glass ceramics according to the invention, the range of the elimination of nuclei which cannot be characterized by structural analysis or very small spinel crystallites (crystallite volume <150 nm 3 ).
Der markierte Temperaturbereich 2 beinhaltet einen deutlichen Peak. Dieser weist auf die exotherme Kristallisationsreaktion sekundärer Kristallphasen an primären Keimen hin.The marked temperature range 2 contains a clear peak. This indicates the exothermic crystallization reaction of secondary crystal phases on primary seeds.
Im Temperaturbereich 3 sind ebenfalls exotherme Reaktionen durch diverse Peaks deutlich, die auf die Kristallisation tertiärer Kristallphasen zurückgeführt werden.In temperature range 3, exothermic reactions due to various peaks are also evident, which are attributed to the crystallization of tertiary crystal phases.
Im Peak- bzw. Dip-freien Temperaturintervall 4 erfolgt eine Reifung, ein Wachstum oder ggf. eine intrinsische Umkristal- lisation ausgeschiedener Phasen. Derartige Prozesse sind jedoch auch im gesamten Temperaturbereich > Tg möglich, also auch in den Temperaturintervallen 1, 2 und 3.In the peak or dip-free temperature interval 4, ripening, growth or, if appropriate, intrinsic recrystallization of excreted phases takes place. However, such processes are also possible in the entire temperature range> Tg, i.e. also in temperature intervals 1, 2 and 3.
Ein scharfer Dip (in Fig. 1: ca. 1415°C) , mit Fp beschriftet, kennzeichnet den Schmelzpunkt der Glaskeramik.A sharp dip (in Fig. 1: approx. 1415 ° C), labeled Fp, indicates the melting point of the glass ceramic.
Zur Herstellung der erfindungsgemäßen Glaskeramiken werden die Keime bzw. Primärkristallite vorzugsweise bei einer Temperatur der unteren zwei Drittel des Temperaturintervalls 1 gebildet, wobei es bevorzugt ist, eine Temperatur innerhalb der unteren Hälfte zu wählen. Noch mehr bevorzugt wird eine Temperatur im unteren Drittel dieses markierten Bereiches 1. Nach Ablauf einer genügend langen Haltezeit bzw. nach der Bildung einer genügend großen Anzahl primärer Kristallite bzw. Keime wird auf eine höhere Temperatur erwärmt, bei der sich die Hauptkristallphasen der Glaskeramik ausscheiden bzw. primäre Kristallite ein erhebliches Größenwachstum zeigen. Eine derartige Temperatur liegt dabei üblicherweise im markierten Temperaturintervall 2 und mindestens 20 K, vorzugsweise mindestens 50 K oberhalb der Keimbildungstempera- tur, wobei ein Temperaturbereich von + 50 K um das Peakmaxi- um im (in Fig. 1 markierten) Bereich 2 angestrebt wird. Bei dieser Temperatur wird die Glaskeramik belassen, bis die ausgeschiedenen Kristallite eine ausreichende Größe erreicht haben.To produce the glass ceramics according to the invention, the nuclei or primary crystallites are preferably formed at a temperature of the lower two thirds of the temperature interval 1, it being preferred to choose a temperature within the lower half. A temperature in the lower third of this marked area 1 is even more preferred. After a sufficiently long holding time or after the formation of a sufficient number of primary crystallites or nuclei, the mixture is heated to a higher temperature at which the main crystal phases of the glass ceramic separate or primary crystallites show considerable size growth. Such a temperature is usually in the marked temperature interval 2 and at least 20 K, preferably at least 50 K above the nucleation temperature. tur, whereby a temperature range of + 50 K around the peak maximum in region 2 (marked in FIG. 1) is aimed for. The glass ceramic is left at this temperature until the precipitated crystallites have reached a sufficient size.
Anschließend wird das Material auf eine weitere höhere Temperatur, üblicherweise aus den Temperaturintervallen 3 und 4, erwärmt. Zur Auskristallisation der tertiären Kristallphasen mit ausreichender Kristallitgröße wird die Glaskeramik auf dieser Temperatur gehalten.The material is then heated to a further higher temperature, usually from temperature intervals 3 and 4. The glass ceramic is kept at this temperature in order to crystallize out the tertiary crystal phases with a sufficient crystallite size.
Die Haltezeiten bei den jeweiligen Temperaturen zur Ausbildung primärer, sekundärer oder tertiärer kristalliner Phasen richtet sich nach deren Wachstumsgeschwindigkeit und beträgt üblicherweise mindestens 15 Minuten, vorzugsweise mindestens 30 Minuten, wobei eine Haltedauer zwischen 60 und 180 Minuten, insbesondere zwischen 90 und 120 Minuten, besonders bevorzugt ist. Die Obergrenze der Haltezeiten liegt üblicherweise bei maximal 60 Stunden, vorzugsweise bei maximal 12 Stunden. In einer Vielzahl der Fälle ist es auch möglich, nach Ausbildung und Reifung primärer Kristallphasen bzw. Keime auf eine einzige höhere Temperatur, z.B. innerhalb des Temperaturintervalls 4 der Fig. 1, zu erwärmen, um dort sekundäre und tertiäre Kristallphasen gleichzeitig aus- bzw. umzukristallisieren.The holding times at the respective temperatures for the formation of primary, secondary or tertiary crystalline phases depend on their growth rate and are usually at least 15 minutes, preferably at least 30 minutes, with a holding time between 60 and 180 minutes, in particular between 90 and 120 minutes, being particularly preferred is. The upper limit of the holding times is usually a maximum of 60 hours, preferably a maximum of 12 hours. In a large number of cases it is also possible, after the formation and maturation of primary crystal phases or nuclei to a single higher temperature, e.g. 1 within the temperature interval 4, in order to crystallize or recrystallize secondary and tertiary crystal phases at the same time.
Bei der Keramisierung des Ausgangsglases erfolgt erfindungs- gemäß die Aufheizung bis zu einer Temperatur kurz unterhalb Tg relativ rasch, d.h. mit 5 - 15 K min"1, insbesondere mit ca. 10 K min"1. Auf die Temperatur zur Ausscheidung primärer Kristallphasen bzw. Keime wird dann langsamer, mit ca. 3 - 8 K min"1, üblicherweise mit ca. 5 K min"1 erwärmt. In einer Vielzahl der Fälle kann die Aufheizgeschwindigkeit auch 0,5 - 3 K min"1 betragen. Die höheren Temperaturen, bei denen sekundäre oder tertiäre Kristallphasen auskristallisieren, können mit sehr unterschiedlichen Heizraten im Bereich 0,5 - 200 K min"1 erreicht werden. Die Festlegung dieser Heizraten erfolgt in Abhängigkeit von den Wachstumsgeschwindigkeiten der jeweiligen Kristallphasen im jeweiligen Matrix-Material.According to the invention, when the starting glass is ceramized, the heating up to a temperature just below Tg takes place relatively quickly, ie with 5-15 K min "1 , in particular with about 10 K min " 1 . The temperature for the precipitation of primary crystal phases or nuclei is then heated more slowly, at about 3 to 8 K min "1 , usually at about 5 K min " 1 . In a large number of cases, the heating rate can also be 0.5-3 K min "1. The higher temperatures at which Crystallizing secondary or tertiary crystal phases can be achieved with very different heating rates in the range 0.5-200 K min "1. These heating rates are determined depending on the growth rates of the respective crystal phases in the respective matrix material.
Die im Folgenden angegebenen Gläser wurden wie folgt dargestellt:The glasses listed below were shown as follows:
In einen Pt/Rh-Tiegel wurden bei 1600 - 1700°C in Chargen von 100 g bis 3 kg das jeweilige Glasgemenge erschmolzen und zu Platten (0,5 - 3 cm Dicke) gegossen. Diese Glasplatten wurden bei Temperaturen Tg+20 K entspannt langsam auf Raumtemperatur abgekühlt .The respective glass batch was melted in a Pt / Rh crucible at 1600-1700 ° C. in batches of 100 g to 3 kg and cast into plates (0.5-3 cm thick). These glass plates were slowly cooled to room temperature at temperatures Tg + 20 K.
Zur Darstellung der Glaskeramiken wurden die Gläser nach der zuvor angegebenen Vorgehensweise wie in der folgenden Tabelle angegeben, thermisch behandelt. Dabei schieden sich Kristallite der unterschiedlichen Kristallphasen aus. Die Kristallisation wurde in ein- bzw. mehrstufigen Temperprogrammen durchgeführt. Dabei bedeutet beispielsweise die Angabe 800°C/2h, 950°C/lh, 1050°C/lh, dass das Glas einer thermischen Behandlung für 2 Stunden bei 800°C, anschließend für eine Stunde bei 950°C und schließlich noch 1 Stunde bei 1050°C unterzogen wurde.To display the glass ceramics, the glasses were thermally treated according to the procedure given above, as indicated in the table below. Crystallites from the different crystal phases separated out. The crystallization was carried out in one-stage or multi-stage tempering programs. For example, the specification 800 ° C / 2h, 950 ° C / lh, 1050 ° C / lh means that the glass undergoes a thermal treatment at 800 ° C for 2 hours, then at 950 ° C for one hour and finally for 1 hour at 1050 ° C.
Spinell konnte als erste auftretende kristalline Phase nachgewiesen werden, deren Ausbildung im Temperaturbereich von ca. 750-900°C nach 1-2 h erfolgte. Das Kristallwachstum des Spinells bzw. die Ausscheidung von Sapphirin oder anderen Kristallphasen wurde in einem zweiten Schritt der thermischen Behandlung zwischen 850°C und 1050°C in ca. 2 h erreicht. Vereinzelt wurde das Kristallwachstum auch durch verlängerte Haltezeiten bei Temperaturen um 900°C erzielt. In der Tabelle bedeuten Sp: Spinell, Sa: Sapphirin, Co:Cordie- rit, Ps :Yttrium-Pyrosilikat, Pc: Yttrium- yrochlor, Xe:Yt- trium-Phosphat (Xenotim) , Ru:Rutil (Ti02) .Spinel was found to be the first crystalline phase to occur, which developed in the temperature range of approx. 750-900 ° C after 1-2 h. The crystal growth of the spinel or the excretion of sapphirine or other crystal phases was achieved in a second step of the thermal treatment between 850 ° C and 1050 ° C in about 2 hours. In isolated cases, the crystal growth was also achieved through longer holding times at temperatures around 900 ° C. In the table, Sp mean: spinel, Sa: sapphirine, Co: cordie rit, Ps: yttrium pyrosilicate, Pc: yttrium yrochlor, Xe: yttrium phosphate (xenotime), Ru: rutile (Ti0 2 ).
Die dargestellten Gläser und Glaskeramiken wurden umfangreich charakterisiert. Der E-Modul und die Biegebruchfestigkeit wurden aus Biegebruchversuchen ermittelt, der KiC-Wert über die Messung von Radialrisslängen nach dem VICKERS-Ver- fahren berechnet. Die Dichte wurde mittels der Auftriebme- thode und der Wärmeausdehnungskoeffizient mittels dilatome- trischer Messungen bestimmt. Die Analyse der Kristallphasen erfolgte mittels Röntgendiffraktometrie. Kristallgefüge und Textur wurden aus rasterelektronenmikroskopischen Aufnahmen abgeleitet. Dabei werden nach Standardpolitur rasterkraftmi- kroskopische Untersuchungen (AFM) durchgeführt, die eine Oberflächentopografie liefern. Die Mittelung der Messwerte führt auf die angegebenen Werte der Oberflächenrauhigkeit . Dabei bedeuten Ra das arithmetische Mittel und rq (oder rms) das geometrische Mittel der Messwerte. PV bezeichnet den Abstand von peak zu valley der Maxima/Minima entlang einer Messstrecke. The glasses and glass ceramics shown were extensively characterized. The modulus of elasticity and the bending strength were determined from bending tests, the K iC value was calculated by measuring radial crack lengths using the VICKERS method. The density was determined by means of the buoyancy method and the coefficient of thermal expansion by means of dilatometric measurements. The crystal phases were analyzed by means of X-ray diffractometry. Crystal structure and texture were derived from scanning electron microscope images. Atomic force microscopic examinations (AFM) are carried out according to standard polishing, which provide a surface topography. The averaging of the measured values leads to the specified values of the surface roughness. Ra means the arithmetic mean and rq (or rms) the geometric mean of the measured values. PV denotes the distance from peak to valley of the maxima / minima along a measurement section.
Anwendungsbeispiele P1853Application examples P1853
Abk.: Sp: Spinell; Sa: Sapphin; Co: Cordierit; Ps: Yttrium-Pyrosilikat; Pc: Yttrium Pryochlor; Xe: Yttrium Phosphat (Xenotim) Ru: Rutil (Ti02) ( ): Phase untergeordneter Bedeutung ?: Phase nicht eindeutig nachweisbar Abbr .: Sp: spinel; Sa: Sapphin; Co: cordierite; Ps: yttrium pyrosilicate; Pc: yttrium pryochlor; Xe: yttrium phosphate (Xenotim) Ru: rutile (Ti0 2 ) (): phase of minor importance?: Phase not clearly detectable

Claims

Kristallisierbares Glas und seine Verwendung zur Herstellung einer hochsteifen, bruchfesten Glaskeramik mit gut polierbarer OberflächePatentansprüche Crystallizable glass and its use for the production of a highly rigid, unbreakable glass ceramic with a surface that can be easily polished
1. Kristallisierbares Glas vom magnesiumhaltigen Alumosili- kattyp zur Herstellung einer hochsteifen, bruchfesten Glaskeramik mit einem E-Modul > 110 GPa gekennzeichnet durch einen Gehalt an1. Crystallizable glass of the magnesium-containing aluminosilicate type for the production of a highly rigid, break-resistant glass ceramic with an elastic modulus> 110 GPa characterized by a content of
5-33 Gew.-% Si02 5-33% by weight Si0 2
25-40 Gew.-% Al203 25-40% by weight Al 2 0 3
5-25 Gew.-% MgO5-25 wt% MgO
0-15 Gew.-% B203 0-15% by weight B 2 0 3
0,1-30 Gew.-% Y203. Ln203, As203 und/oder Nb205 0,1-10 Gew.-% P205.0.1-30% by weight Y 2 0 3 . Ln 2 0 3 , As 2 0 3 and / or Nb 2 0 5 0.1-10% by weight P 2 0 5 .
2. Glas nach Anspruch 1, dadurch gekennzeichnet, dass es einen Alkaligehalt < 2 Gew.-% aufweist.2. Glass according to claim 1, characterized in that it has an alkali content <2 wt .-%.
3. Glas nach einem der vorhergehenden Ansprüche dadurch gekennzeichnet, dass das Glas Übergangsmetalloxide in einer Menge von maximal 10 Gew.-% enthält.3. Glass according to one of the preceding claims, characterized in that the glass contains transition metal oxides in an amount of at most 10 wt .-%.
4. Glas nach Anspruch 3 dadurch gekennzeichnet, dass die Übergangsmetalloxyde Mn02, Fe203, NiO, CoO, Cr203, V205, Mo03, W03 sind.4. Glass according to claim 3, characterized in that the transition metal oxides are Mn0 2 , Fe 2 0 3 , NiO, CoO, Cr 2 0 3 , V 2 0 5 , Mo0 3 , W0 3 .
5. Glas nach einem der vorhergehenden Ansprüche dadurch gezeichnet, dass das Glas 0 - 5 Gew.-% CaO, 0 - 5 Gew.-% SrO und/oder 0 - 5 Gew.-% BaO enthält. 5. Glass according to one of the preceding claims, characterized in that the glass contains 0-5% by weight of CaO, 0-5% by weight of SrO and / or 0-5% by weight of BaO.
6. Glas nach einem der vorhergehenden Ansprüche dadurch gekennzeichnet, dass es 0 - 12 Gew.-% Ti02, 0 - 10 Gew.-% Zr02 und/oder 0 - 20 Gew.-% ZnO enthält.6. Glass according to one of the preceding claims, characterized in that it contains 0-12% by weight of Ti0 2 , 0-10% by weight of Zr0 2 and / or 0-20% by weight of ZnO.
7. Glas nach einem der vorhergehenden Ansprüche erhältlich durch Entspannen bei einer Temperatur von 5 - 50°C oberhalb Tg für zwei Minuten bis einer Stunde.7. Glass according to one of the preceding claims obtainable by relaxing at a temperature of 5-50 ° C above Tg for two minutes to one hour.
8. Glaskeramik erhältlich durch Erwärmen eines Glases nach einem der Ansprüche 1-7.8. Glass ceramic obtainable by heating a glass according to any one of claims 1-7.
9. Verwendung der Gläser nach einem der Ansprüche 1 - 7 zur Herstellung einer Glaskeramik.9. Use of the glasses according to one of claims 1-7 for the production of a glass ceramic.
10. Verwendung nach Anspruch 9 dadurch gekennzeichnet, dass man das Glas an mittels Differentialthermoanalysen ermittelten Haltekurven solange erwärmt, bis kristalline Phasen ausgeschieden werden.10. Use according to claim 9, characterized in that the glass is heated on holding curves determined by means of differential thermal analysis until crystalline phases are eliminated.
11. Verwendung nach Anspruch 9 oder 10 dadurch gekennzeichnet, dass man das Glas zur Ausbildung von Primärkeimen mindestens 30 Minuten auf eine erste Keimbildungstemperatur und danach mindestens 30 Minuten auf eine zweite Hauptkristallisationstemperatur erwärmt, bei der auf den Primärkeimen Kristallphasen der Klassen Spinell, Sapphirin und/oder Cordierit gebildet werden und dass gegebenenfalls zur Ausbildung von Kristallphasen der Klassen Xenotime (YP04) Yttriumpyrosilikat (YSi207) sowie Yttro- pyrochlor (Y2Ti07) und/oder Rutil (Ti02) mindestens 0,5 Stunden weiter auf eine höhere Temperatur erwärmt wird.11. Use according to claim 9 or 10, characterized in that the glass for the formation of primary nuclei is heated to a first nucleation temperature for at least 30 minutes and then to a second main crystallization temperature for at least 30 minutes, in which crystal phases of the classes spinel, sapphirin and / or cordierite are formed and that optionally for the formation of crystal phases of the classes Xenotime (YP0 4 ) yttrium pyrosilicate (YSi 2 0 7 ) and ytrophyrochlorine (Y 2 Ti0 7 ) and / or rutile (Ti0 2 ) continues for at least 0.5 hours a higher temperature is heated.
12. Verwendung nach Anspruch 9 - 11 zur Herstellung von Magnetspeicherplatten, magneto-optischen Speichern und Spiegelträger . 12. Use according to claim 9 - 11 for the production of magnetic storage disks, magneto-optical memories and mirror carriers.
EP03757685A 2002-09-27 2003-09-26 Crystallisable glass and the use thereof for producing extremely solid and break-resistant glass-ceramics having an easily polished surface Withdrawn EP1558535A1 (en)

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PCT/DE2003/003227 WO2004031089A1 (en) 2002-09-27 2003-09-26 Crystallisable glass and the use thereof for producing extremely solid and break-resistant glass-ceramics having an easily polished surface

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