KR20170013317A - Transparent spinel ceramics and methods for the production thereof - Google Patents

Abstract

The present invention relates to the field of ceramics, for example, transparent spinel ceramics, which can be used as protective ceramics, or a method of making the same. It is an object of the present invention to provide a transparent spinel ceramic with an in-line transmittance in excess of 82% in the infrared wavelength range measured between 1000 nm and 2500 nm at a sample thickness of ≥ 3 mm, with no visible defect as far as possible will be. This object is achieved by transparent spinel ceramics in the infrared wavelength range, which is achieved by the addition of 0.005 to < 0.2 mass% of CaO and / or 0.005 to < 0.5 mass% SrO and / or 0.005 to & , A homogeneously distributed additive of calcium and / or strontium and / or barium, present in concentrations respectively expressed as oxides, with a maximum total amount of 0.5% by mass, with a sintered magnesium aluminum spinel having an average grain size of &lt; .

Description

TECHNICAL FIELD [0001] The present invention relates to transparent spinel ceramics,

The present invention relates to the field of ceramics technology, and more particularly to the field of ceramic technology, which can be used for applications that have increased mechanical load, such as, for example, protective ceramics, or have increased optical quality requirements, And a method for manufacturing the same.

For example, there has been a long need for transparent ceramics to combine with the beneficial properties of ceramics with respect to hardness and strength and with the maximum possible transparency. However, to date, it has not been achieved to the extent required by longstanding efforts by experts. Moreover, due to certain excessively different criteria, the achieved results are often incomparable, so that the actual knowledge state for the transparent ceramic is at least confusing and unclear.

Accordingly, terms applied in connection with the prior art also cited within the scope of the present invention are described and defined below.

The terms "transparent" or "translucent" are not clearly distinguished from each other in the prior art. Thus, the transparent material is understood as a material having an in-line transmittance of more than 50% at a visible wavelength of about 1 mm and about 600 nm.

In order to calculate the transparency of the material, the actual in-line transmission (RIT) measured using a narrow aperture angle of approximately 0.5 [deg.] To exclude the scattered light from the measured intensity This is a reliable variable, for example, as disclosed in EP 1053983A (Yamamoto et al.) Or by Apetz et al., J. Am. Ceram. Soc. 86 (2003) 480. According to Apetz, the difference between the in-line transmittance and the RIT determined using a conventional spectrometer operating at an effective aperture angle of 3-5 °, as well as at shorter wavelengths (resulting in more pronounced scattering losses) and It is particularly noticeable over the entire visible range, while the features associated with these measurements are not significant in the infrared range.

In the case of absent or extremely low light absorption, the transmission of an optically homogeneous material, such as glass, or a single crystal is determined by the material-specific reflectance (n), which is determined by the reflectance (n) ) is limited only by the _{R s = ((n-1} ) / (n + 1)) 2. Considering multiple reflections, the theoretical maximum transmittance ( _Tmax ) obtained for highly transparent materials is _Tmax = (1-R) and R = 2Rs / (1 + Rs), or for materials with low transmittance, That is, for neglected multiple reflective materials, T _max = (1-Rs) ² ; For MgO.Al ₂ O ₃ spinel whose reflectance is in the visible range of 1.712 to 1.736, the T _max is approximately 86.9%.

As a special advantage of the very high RIT for the flexibe design of the transparent product for the individual application, when the theoretical maximum ( _Tmax ) is reached, the effect of the thickness is reduced, while conversely, Depending on the thickness of the material, the potential scattering losses of the path are greater, and transparency is then ensured for very thin parts.

As such, this type of thickness effect is evidence for the presence of significant light-scattering - that is, low transparency-the cause of potential very high transmittance values due to too large hole angles, and the measurement of actual in- .

Unlike the potential absorption, RIT is substantially reduced for T _max by the following processes as light passes through the tissue of the sintered polycrystalline ceramic:

1. diffusion scattering (depending on size and number of pores) in the pores, and

2. In non-cubic ceramics such as corundum (? -Al ₂ O ₃ ), especially in the birefringence of each transition of the light beam from one crystal of the additional tissue to the next crystal Additional optical scattering caused by.

Thus, the scattering loss should be kept small in all sintered ceramics by the minimum possible residual porosity of <0.1%, preferably <0.01%, and preferably by a pore size smaller than the optical wavelength.

Since only the prior scattering mechanism occurs in a cubic sintered ceramic, its transparency is not immediately affected by particle-size, unlike a ceramic with birefringent (non-cubic) crystals. This situation, which is dependent on the crystal structure, is that the ceramics with a cubic crystal lattice are preferred for transparent applications, and the harder, more intense (e.g., ceramics) ceramics such as sintered corundum ceramic or tetragonal zirconia ceramics, The reason why non-cubic ceramics merely performs a secondary action is clarified: The most advanced, ie, the sintered corundum with the smallest pore size of the finest particles (three-sided) has> 70% RIT at> 1 mm thickness Tetragonal Zr ₂ O ceramics exhibit smaller transparency while measurements between 80% and 85% are greater, even at thicknesses closer to the theoretical maximum described above, for example MgO.Al ₂ O ₃ Spinel (cubic) was repeatedly observed.

However, most of the cube transparent ceramics known in the prior art exhibit lower values for hardness, scratch resistance and strength. These improvements in mechanical properties are only possible through the reduced particle size of the sintered texture. An example of this is known from US 7247589 (Krell et al.), And this type of power generation can be achieved with this type of fine-crystal sintered structure having an average grain size of <10 μm or <1 μm, Respectively. However, under a constant sintering temperature, this would collide with the requirements of the above-mentioned minimum residual porosity or a high relative sintering density of > 99.9%, or preferably> 99.99%, which in turn produces micro- A visible defect in the form of an incomplete sintered partial area of the tissue, or reduced transparency.

In addition to various efforts in, for example, the optimum (and pressure-based) sintering systems described in EP 0332393 A (Shibata et al.), And also through the use of increasingly finer nanopowders (J. Sintered spinel ceramics by changing the stoichiometry (EP 1873129 A, Sasame et al.), Phys. D; Appl. Phys. However, to date, optical quality is still unsatisfactory and remains within the visible range.

For this reason, special attention has been paid to the sintering-enhancing doping from time to time, whereby special attention has been paid to optimize temperature reduction and, thus, grain growth-reduction doping. The best known doping known for semitransparent spinel ceramics consists of doping to form a liquid phase using 0.25 mass% CaO in an early example (RJ Bratton, J. Ceram. Soc. 57 (1974) 7, 283-286) Extensive experiments. The production of translucent spinel ceramics with a line transmission of < 40% of the visible range for thin samples of 0.37 mm - 0.95 mm has been described. Subsequent developments have increased the effectiveness of liquid phase sintering, especially by LiF doping (US 2011 / 0028303A, Villalobos et al.), But this also typically resulted in the formation of visible defects (G. Gilde et al., J. Am. Ceram., Soc., 88 (2005) 10, 2747). Though these defects can be minimized as part of this type of liquid sintering, they can not be avoided.

Background of the increasing effort in doping, preferably as part of a pure solid phase sintering, or minimizing the formation of liquid phase, is to achieve a transparent spinel ceramic result similar to that achieved with years of known MgO doping in sintering of Al ₂ O ₃ ceramics ; The results show, on the one hand, the promotion of diffusion by the atomic effect of the solid solution of the doped portion in the lattice of the main phase of the ceramic, and thus the promotion of dense sintering; On the other hand, it is a reduction of the grain growth of the ceramic by the second phase particles in the grain boundaries, as described by von Peelen (JGJPeelen, Dissertation, TH Eindhoven, 1977). In view of the combination of high transparency with the finest possible particle size of the tissue as a preliminary condition for improved mechanical properties, the following examples are particularly named:

[K Tsukuma, J. Ceram. Soc. Japan 114 (2006) 10, 802-806) achieved a significant reduction in the sintering temperature by doping B ₂ O ₃ of 0.015-0.150 mass%, but for 1-mm thick samples, about 600-650 nm Only a limited improvement in the transmittance can be expected since it initiates a transmission of 83%. Although there is no mention of the frequency and magnitude of the residual visual effects, such defects can be attributed to the formation of a localized liquid phase which can be assumed to be due to the B ₂ O ₃ additive, similar to the case of LiF doping, Can be assumed to be based.

According to EP 2112127A1 (A. Ikesue), very high transmission values close to the theoretical limits are known for sintered spinel samples of 10-mm thickness, which is due to the addition of MgF ₂ / AlF ₃ co-doping Is produced by hot isostatic pressing (HIP) at a high temperature (1780 DEG C). However, the actual cause of the achieved transmission is unclear; Despite years of effort, the inventors have not succeeded in reproducing the results published in the patent application. Moreover, successful studies of such doping by other authors were not known.

According to FR 0334760 B1 (P.Bergez et al) 0.5-5 mass% MgO additive is known, which is preferably added during the synthesis of the spinel powder and does not constitute the actual sintering doping in the sense above, Because MgO only compensates the known evaporative effect of MgO from the spinel lattice at high temperature sintering temperatures. However, without these extra MgO types, several documents have been published which achieve a similar transmittance of approximately 80% at a wavelength of 600-650 nm for 3-mm thick samples such as in FR 0334760B1.

A particularly broad range of doping additives for spinel have been reported [Sarkar et al, Ceram. Inl. 29 (2003) 1, 55-59], regardless of the quality of the transparent ceramics. TiO ₂ , V ₂ O ₅ , and B ₂ O ₃ The additives have been described in terms of their effect on the reactive sintering of the MgO / Al ₂ O ₃ mixture, where only TiO ₂ has a positive effect and the effect on the sintering of the pre-calcined spinel powder is not known. The list of documents cited in this publication also describes Y ₂ O ₃ doping and other rare-earth doping and MnO ₂ and is nonetheless not related to the production of transparent ceramics.

On the other hand, TiO ₂ doping to sintered spinel has been frequently re-discussed, and the only effect of TiO ₂ appears to be insufficient for satisfactory transmission. Thus, according to FR 2917404 B1 (Bernard-Granger et al.), Co-doping of TiO ₂ with at least one further additive selected from the group of ZrO ₂ , CaO and MgO is known. This doping is then generally to improve the transmission of completely different ceramics of MgAl ₂ O ₄ spinel, cubic ZrO ₂ or Y-Al garnet (Y ₃ Al ₅ O ₁₂ ). This universal efficacy may indicate the formation of a liquid phase, but this will be associated with the risk of the aforementioned disadvantages of liquid-phase sintering of the transparent ceramic. The exemplary embodiment for spinel shows a very high in-line transmission of 84.8% for a thin sample of only 1.3 mm, so a definite improvement in permeability can also be expected. No mention of the frequency and size of the residual visual effects is made here.

A similar attempt at co-doping to improve dense-sintering has not been realized with the obvious benefit of this doping, but using the combination of TiO ₂ and CoCO ₃ [Tsai et al., Mater. Sci. Eng. B177 (2012) 13, 1133-1137).

The formation of the spinel reactivity of MgO / Al ₂ O ₃ mixture and the effect of ZrO ₂ The effect of doping - regardless of transparency - [J.Kim, phD. dissertation, Case Western Reserve University, 1992]. According to the study, ZrO ₂ Doping decreases the sintering speed of spinel and increases the formation of Al ₂ O ₃ precipitation in Al-rich compounds. Both of these results contradict the purpose of improved in-line transmission and minimization of visible defects.

One of the earliest doping studies on transparent spinel ceramics is to have a 0.25% CaO addition [RJ Bratton, J. Am. Ceram. Soc. 57 (1974) 7, 283-286], but could not achieve a transmittance of 40% in the visible wavelength range; The material was kept translucent. [Huang et al., J. Am. Ceram. Soc. 80 (1997) 12, 3237-3241) studied the effect of CaCO ₃ on the dense-sintering of spinel as co-doping for LiF, but there was no objective for permeability. Applicants' attempts to use CaO doping of &gt; = 0.2 mass% can in this way reduce the sintering temperature and create very fine-grained transparent spinel structures, but instead the actual in- Percent reduction and is associated with the formation of visible defects in the transparent ceramic volume. The partial dendritic structure of these defects led to the conclusion that this type of CaO doping also achieved a temperature-lowering effect by forming a local liquid phase, as opposed to the single-phase conditions required in the defect-free transparent ceramic, Precipitation of external phases with different reflectivities can withstand only when the size is small compared to the shorter wavelength of the optical spectrum.

From element of the periodic table an alkali earth (alkaline earth group), a so-called "BAM" phosphor (phosphor) of the formula BaMgAl ₁₀ O ₁₇ is typically doped with a europium (europium) or strontium (US 561 1959A). However, this type of The presence of the compound does not suggest a potential effect of Ba, Sr or Eu as a sintering additive for Mg-Al spinel ceramics. Also, transparent spinel ceramics according to DE 10 2002 220 257 A1 are known, Europium, barium, or combinations thereof, or oxides of ten other elements listed without mentioning reasons, but still the required permeability is limited to grain growth at an average value of &gt; No effect or result has been stated for any doping, and this publication also discloses that for high-transmittance, fine-crystalline spinel ceramics, I have not started teaching.

US7799267 B2 is also sintered-increasing doping investigation to illustrate the direction of the loss of developer in, the transparent spinel ceramic manufacture and also a transparent Y-Al _{garnet, Ce 2 O 3, Y 2} O 3, SC 2 O 3, and Lu ₂ An exceptional preparation by O ₃ of TEOS (tetraethyl orthosilicate or tetraethoxysilane) additive is described here as a special technique of "tape casting slurry material for the production of transparent ceramic materials", while on the other hand it is described at the outset that "lithium oxide, titanium oxide, zirconium The appearance or criterion of the property results, which may be any of the oxides, barium oxides, calcium oxides, magnesium oxides, strontium oxides, boron oxides, and mixtures thereof, may also potentially be used as "sidings" On the other hand, on the other hand, however, the potential range of this possibility is higher at 1700 ° C (without the published permeability results) of spinel specimens in the case of other ceramics To kkeok motivated in FIG located as opposed to the actual start of the high sintering temperature; Precluding the manufacture of micro-crystalline tissue; And nonetheless allows for limited transparency: as a result of the unique permeability of YAG ceramics of 2.7 mm thickness at wavelengths of 600 nm-650 nm due to the high content of organic additives required for the tape casting described above, it was 81.20% -81.27% US 7799267B2.

Although the publication thus describes sintering-augmentation doping for spinel ceramics from almost all groups of the periodic table, achieving high-transmittance while avoiding visible defects substantially and achieving micro-particle textures with high mechanical parameters For a doping ion in a manner that enables this at the lowest possible sintering temperature, no system can be identified yet. Further, to the literature of the magnesium aluminum spinel which does not include the extension data, for example similarly to the solid solubility amount of the periodic table of the individual element as a function of temperature and atmospheric pressure, and this is due to several known came to the Al ₂ O ₃ years.

In view of the limited prior successes exemplified in the prior art, one object of the present invention is to provide a method and a method for fabricating a semiconductor device that is free of visible defects, or has defects of size > In-line transmission in the wavelength range of infrared rays measured between 1000 nm and 2500 nm at the sample thickness of the transparent spinel ceramics.

A further object of the present invention is to provide a method and apparatus for measuring defects which do not include visible defects or contain defects at a maximum of &lt; 300 / cm < 3 & Ray transmittance of RIT &gt; 80% in the wavelength range of visible visible light.

It is a further object of the present invention to provide a method of making this type of transparent spinel ceramic at the lowest possible sintering temperatures.

The above objects are achieved by the present invention in the invention disclosed in the claims. An advantageous implementation becomes the subject matter of the dependent claim.

The spinel ceramics according to the present invention which are transparent in the infrared wavelength range are respectively expressed as oxides of CaO and / or 0.005 to 0.5 mass% of SrO and / or 0.005 to 0.5 mass% of BaO, respectively, in an amount of 0.005 to 0.2 mass% And a sintered magnesium aluminum spinel having an aggregate of 0.5% by mass of homogeneously distributed additives of calcium and / or strontium and / or barium present in the concentration and having an average tissue particle size of? 10 μm.

The spinel ceramics according to the invention which are transparent in the visible wavelength range are expressed as oxides of CaO and / or 0.005 to <0.3 mass% SrO and / or 0.005 and <0.25 mass% of BaO, respectively, in an amount of 0.005 to <0.2 mass% Consist of a sintered magnesium aluminum spinel having a maximum of 0.5% by mass of the total of homogeneously distributed additives of calcium and / or strontium and / or barium present in the concentration and having an average tissue particle size of? do.

Preferably, the mean grain size of the sintered magnesium aluminum spinel is < 5 탆, preferably <2.5 탆, more preferably <1 탆.

Also preferably, for the transparent spinel ceramic in the infrared wavelength range, there is a homogeneously distributed additive with a maximum total addition of 0.3 mass%.

Likewise, in the case of transparent spinel ceramics in the visible light wavelength range, there is a totally homogeneously distributed additive with a maximum total mass of 0.2 mass%.

More preferably, calcium is present as an additive represented by CaO at a concentration of 0.01 to 0.1 mass%.

Also preferably, for transparent spinel ceramics in the infrared wavelength range, strontium and / or barium are expressed as SrO and / or BaO, 0.01-0.4 mass% SrO and / or 0.01-0.4 mass% BaO Concentration additive, wherein up to 0.3 mass% of the additive of strontium and / or barium is present.

Likewise, in the case of transparent spinel ceramics within the wavelength range of visible light, strontium and / or barium are expressed as SrO and / or BaO, 0.01-0.2 mass% SrO and / or 0.01-0.15 mass% BaO, Concentration additive, wherein up to 0.2 mass% of the additive of strontium and / or barium is present.

The spinel ceramics according to the invention which are transparent in the infrared wavelength range are characterized in that they are> 82%, preferably> 84%, more preferably> 85% in phosphorus at least in the infrared wavelength range, measured between 1000 nm and 2500 nm, Line transmission.

The spinel ceramics according to the invention which are transparent in the visible light wavelength range are characterized in that they are> 80%, preferably> 82%, more preferably> 84%, in the range of at least visible light wavelength, measured between 600 nm and 650 nm, RIT is shown.

It is preferable that the spinel ceramic according to the present invention does not contain a visible defect.

Similarly, it is preferred that the spinel ceramic according to the present invention contains visible defects of more than 20 mu m at a frequency of 300 / cm3, preferably 50 / cm3 to 150 / cm3.

And also if there is an HV10 Vickers hardness of &gt; 12.5 GPa.

In the method for producing transparent transparent spinel ceramics in the wavelength range of infrared rays according to the present invention, it is preferred that in the case of an undissolved compound containing Ca, Sr and Ba and / or a compound containing Ca, Sr and Ba dissolved in water and / 0.005 to <0.2 mass% of CaO and / or 0.005 to <0.5 mass% of SrO and / or 0.005 to <0.5 mass% of BaO in the form of a compound containing Ca, Sr and Ba dissolved in an organic solvent Of the total amount of calcium and / or strontium and / or barium additive in the concentration of 0.5% by mass, and the additives are homogeneously distributed, and then the materials are sintered to form a transparent spinel ceramic .

In the method of producing transparent transparent spinel ceramics in the wavelength range of visible light according to the present invention, it is preferable to use a compound containing Ca, Sr, and Ba dissolved in an undissolved compound containing Ca, Sr, and Ba and / Or an oxide of 0.005 to 0.2 mass% CaO and / or 0.005 to 0.3 mass% SrO and / or 0.005 to 0.25 mass% BaO in the form of a compound containing Ca, Sr and Ba dissolved in an organic solvent The addition to the maximum sum of 0.3% by mass of magnesium and aluminum spinel powder of the additive of calcium and / or strontium and / or barium in the concentration to be expressed is carried out, the additives are homogeneously distributed and then the materials are sintered to form a transparent spinel ceramic .

Preferably, the addition of the additive is carried out as part of the impregnation or infiltration by the additive into the dry ceramic body pores during slurry preparation or packing of the ceramic, Or a solution according to the invention containing Ca, Sr and / or Ba and a wet magnesium aluminum spinel body.

By means of the solution according to the invention it is possible to obtain a solution which does not contain visible defects or which contains the bond in a low frequency of up to 300 / cm3 for defects of the order of &gt; 20 mu m, Transparent spinel ceramics having an average particle size of &lt; RTI ID = 0.0 &gt;# 10 &lt; / RTI &gt; having an in-line transmission of greater than 82%

Which has an average grain size of &lt; 10 탆 and is present in a concentration of 0.005 to <0.2 mass% CaO and / or 0.005 to <0.5 mass% SrO and / or 0.005 to <0.5 mass% BaO, The transparent spinel ceramics in the infrared wavelength range consisting of sintered magnesium aluminum spinel having a total of up to 0.5% by mass of additives of calcium and / or strontium and / or barium.

Further, according to the solution according to the present invention, in the case of defects having no visible defect or having a size of &gt; 20 mu m, the bond is contained at a low frequency of a maximum of &lt; 300 / cm &lt; 3 & Transparent spinel ceramics having an average particle size of &lt; RTI ID = 0.0 &gt; 10 &lt; / RTI &gt; um, having an actual in-line transmittance of RIT> 80% at least in the wavelength range of visible light measured between.

This is because the presence of a concentration of 0.005 to <0.2 mass% CaO and / or 0.005 to <0.3 mass% SrO and / or 0.005 to <0.25 mass% BaO, each having an average tissue particle size of? By weight of a transparent spinel ceramic in the visible light wavelength range consisting of sintered magnesium aluminum spinel having a total of 0.3% by mass of a homogeneously distributed additive of calcium and / or strontium and / or barium.

 Further, according to the solution according to the present invention, it is possible to first disclose a method for producing a transparent spinel ceramic of this type at the lowest possible sintering temperature.

Again, this means that for dissolved spinel ceramics in the infrared wavelength range, an undissolved compound containing Ca, Sr and Ba and / or a compound containing Ca, Sr and Ba dissolved in water and / or a Ca , Calcium present in concentrations expressed respectively as oxides of 0.005 to <0.2 mass% CaO and / or 0.005 to <0.5 mass% SrO and / or 0.005 to <0.5 mass% BaO, in the form of compounds containing Sr and Ba, And / or a total of up to 0.5% by mass of the additive of strontium and / or barium is added to the magnesium aluminum spinel powder, the additives are homogeneously distributed, and then the materials are sintered to form a transparent spinel ceramic.

For transparent spinel ceramics in the range of visible light wavelengths, the production of this type of transparent spinel ceramic at the lowest possible sintering temperature is carried out by dissolving the undissolved compounds containing Ca, Sr and Ba and / or Ca, Sr and 0.005 to <0.2 mass% CaO and / or 0.005 to <0.3 mass% SrO and / or 0.005 to <0.25 mass in the form of a compound containing Ca and Sr and Ba dissolved in a compound containing Ba and / % BaO in a total concentration of 0.3% by mass of calcium and / or strontium and / or barium additive, expressed as oxides, respectively, is added to the magnesium aluminum spinel powder, the additives are homogeneously distributed, and then the transparent spinel ceramic By sintering the materials.

In the case of additives, a change in the upper limit of the concentrations to be used depends on the different atomic weights, so a similar molarity can already be achieved using the addition of a smaller mass of Ba than in the case of Sr or Ca, for example.

A somewhat different upper limit of the additive to be used should also be considered whether the spinel ceramic is to be used only in infrared applications, or whether it should also have high transparency in the visible range.

Magnesium aluminum spinel, which is described as a spinel ceramic within the scope of the present invention, also means a compound of the MgO x Al ₂ O ₃ type having an x value in the homogeneity range of a known phase diagram I understand. Further, according to the present invention a sintered spinel ceramics are additives and / or contain doped and is insoluble in the spinel lattice, or or impurities or insoluble impurities MgO part or small precipitates of Al ₂ O ₃ part dissolved in the spinel lattice , The content of which is so low that the resulting optical scattering or absorption does not inhibit the transmission achieved according to the invention.

Within the scope of the present invention, sintering is understood as a certain densification determined by a diffusion process of a body made by powder technology, without applying or applying pressure, and without limitation of specific atmospheric pressure or vacuum.

According to the present invention, the infrared wavelength range is understood as a wavelength range within the lower to middle infrared wavelength range, such as between about 800 nm and 6000 nm.

According to the present invention, the visible wavelength range is understood as a wavelength range of approximately 350 nm to 750 nm.

In principle, a plurality of additives of calcium, strontium and barium according to the invention can also be incorporated into the spinel ceramic. However, in order to prevent the formation of visible defects and the transmission-reduction of heterogeneous phases in the volume of the transparent spinel ceramic in the wavelength range of infrared rays according to the present invention, or to limit these defects to a minimum, 0.5% by mass, preferably 0.3% by mass, should be considered as the upper limit of the sum. In order to prevent the formation of visible defects and the transmission-reduction of heterogeneous phases in the volume of transparent spinel ceramics in the wavelength range of the visible light ray according to the present invention, or to limit these defects to a minimum, within the maximum possible range, As the upper limit, 0.3 mass%, preferably 0.2 mass%, should all be considered.

For physical reasons, the transparent spinel ceramics within the wavelength range of visible light according to the present invention also meet the transparent standard of transparent spinel ceramics within the wavelength range of infrared rays according to the present invention. However, transparent spinel ceramics within the wavelength range of infrared light can meet transparency transparency standards of transparent spinel in the wavelength range of visible light only if the criteria of the additive part of transparent spinel ceramic within the wavelength range of visible light are met.

To avoid or minimize potential liquid formation, the spinel ceramics according to the invention preferably do not include doping or other additives of elements other than alkaline earth element groups. Generally, raw material-related and process-related impurities in amounts up to about 0.1% by mass can sometimes be avoided and may be contained in the spinel ceramics according to the present invention.

For example, when compacts made of spinel powder doped with the present invention and having a specific surface area of about 30 m &lt; 2 &gt; / g are produced, by the additives according to the invention based on Sr compounds or Ba compounds, The sintering temperature alone is significantly changed compared with spinel ceramics according to the present invention, the powder is sintered without pressure sintering up to a relative density of 96% -98% with theoretical density of closed pores, and subsequent hot isostatic pressing HIP) is unchanged; However, the sintering temperature is lowered by about 50 ° C to 100 ° C for the spinel ceramics according to the present invention doped with? 0.2% by mass CaO. Although the required sintering temperature can be increased somewhat by Sr or Ba containing additives of spinel ceramics according to the invention (approximately 1525 ° C for 1510 ° C by undoped spinel ceramics), at least two surprising effects The average tissue particle size of all spinel ceramics doped in accordance with the present invention (calculated as 1.56 times the average fiber length by conventional intervening segment analysis) is typically &lt; 10 [mu] m Preferably between 0.3 탆 and 1.0 탆, and is often narrower than 0.4 탆 to 0.7 탆. These micro-crystalline structures produce greater hardness, with virtually full densification of transparent spinel ceramics, which has an HV10 Vickers hardness between 12.5 GPa and 15 GPa (10 kg of indenter and 98 N test load For example, frequently 14 GPa to 14.5 GPa. A similar average tissue particle size and hardness is also achieved by high Ca doping known since Bratton 1974, but is then followed by optical scattering (e.g.,> 3 mm in haze thickness determined in accordance with DIN 5036-1 of this type of ceramic, %) And a low RIT as described above. According to the doping according to the invention, these disadvantages are avoided and the actual in-line transmittance RIT &gt; 80% for a wavelength ranging between 600 nm and 650 nm at a sample thickness of 3 mm, Combine low contents. These defects are mainly smaller, incompletely sintered tissue areas. Depending on the type and amount of doping, the frequency of these defects is sometimes in the range of 50 / cm &lt; -1 &gt; / 150 / cm &lt; 3 &gt;, but in the undoped spinel ceramics according to the prior art, Lt; 3 &gt; / cm &lt; 3 &gt; in each case.

The concentration of the additives higher than the concentration according to the invention must be avoided because it causes photo-scattering precipitation of heterogeneous in the spinel structure, which in turn can reduce the in-line transmission and also create visible defects. On the other hand, the concentration of the additives on the lower limit according to the invention is necessary for the important effects of the additives.

The additives according to the invention can also be used in the form of oxides such as oxides CaO, SrO and / or BaO and also in the form of other compounds containing Ca, Sr and / or Ba, i.e. also in the form of carbonates, nitrides, May be added to the powder. In each case, the observation of the concentrations expressed as oxides in accordance with the present invention is therefore important on the one hand and is important as proper spatial homogenization of the spinel powder and additives. For example, this homogenization can be caused by the particularly intensive scattering milling of coupled spinel powder with additives in the ball mill, as has been known for decades for the homogenization of MgO doping in Al ₂ O ₃ among others. On the one hand, this homogenization step ensures the homogeneous presence and sintering-enhancing effect of the doping at the fine level through the sintered body, while preventing the precipitation formation on the photo-scattering heterogeneous phases, Lt; / RTI &gt;

A particular advantage of the solution according to the invention in comparison with the prior art is that the actual specifications of the additives are taken in terms of type and quantity, in particular in relation to the upper limit of the mean tissue particle size, relative to the total amount, According to the preparation according to the present invention, spinel ceramics having very specific and very high transmittance values in different wavelength ranges and having defects with no visible defects or with low frequency are produced wholly in the spinel powder and produced according to the invention.

In the following, the present invention will be described in more detail by way of several exemplary embodiments.

Example 1

0.1% by weight of CaO powder (Merck) was added to the MgAl ₂ O ₄ suspension of 29.8% by mass of spinel powder (S30CR, Baikowski), and 69.6% by mass of deionized water and 0.6% by mass of Dolapix CE64 scattering aid Zschimmer & Schwarz) were dissolved in a laboratory attritor after two hours of deagglomeration milling.

With respect to the mass of the spinel powder, drying of the suspension occurred after the addition of 0.6% by weight of polyvinyl alcohol (Mowiol 4-88, Zschimmer & Schwarz) and 2.0% by weight of glycerol and strong homogenization by means of a stirrer.

The dried screen-granulated packing powder was pre-pressurized for shaping to form a circular disk of 30 mm diameter and 9 mm thickness and then pressed again in the CIP process. After thermally recombining in air at 800 DEG C for two hours, the Compacks were sintered at 1450 DEG C for two hours in air and then subjected to hot isostatic pressing (HIP) for 15 hours in an argon atmosphere for 15 hours to achieve permeability at 1420 DEG C - Pressurized. The temperature specifications were generated specifically for these packing powders as a result of optimization. Different temperatures are needed for different types of doped packings.

The density of the generated transparent discs is &gt; 99.9% of the theoretical density. The average tissue particle size (calculated as 1.56 times the measured average fiber length) was 0.68 μm.

The HV10 Vickers macro hardness, HV10 = 14.0 GPa, as measured on the polished portion produced by the ceramic technique.

In a plane-parallel manner, the disks were polished to a thickness of 3 mm and 5 mm and polished to a surface roughness R _z <0.03 μm on both sides.

Actual in-line transmittance (RIT; GHz LCRT-2005-S spectrophotometer) measured at 640 nm wavelength on these disks was 84.7% for 3 mm thick discs and 84.5% for 5 mm thick discs.

The in-line transmission measured at a wavelength of 2000 nm by spectrometer 400 (Perkin-Elmer, Waltham, Mass., USA) was 89% for a 5 mm thick disc and this predicted theoretical transmission for this wavelength within the measurement accuracy range Respectively.

For the characteristics of visible defect clusters on the size of 20 μm, sample sections of 12 mm x 12 mm size were recorded using a high-resolution scanner. Visible defects were counted for the graph image of this section extended by a factor of 20. Here, a defect concentration of 246 / cm 3 was determined.

Example 2

50 ml of a liquid strontium nitride solution was added to a MgAl ₂ O ₄ suspension of 29.8 mass% spinel powder (S30CR, Baikowski), 69.6 mass% deionized water and 0.6 mass% Dolapix CE64 (Zschimmer & Schwarz) Lt; / RTI &gt; after two hours of anti-agglomeration milling. The concentration of the doping solution was selected so that the content of strontium oxide SrO in relation to the mass of the spinel powder was 0.125 mass%.

With respect to the mass of the spinel powder, drying of the suspension occurred after the addition of 0.6% by weight of polyvinyl alcohol (Mowiol 4-88, Zschimmer & Schwarz) and 2.0% by weight of glycerol and strong homogenization by means of a stirrer.

The dried screen-granulated packing powder was pre-pressurized for shaping to form circular disks of 30 mm diameter and 9 mm thickness and then pressed again in the cold isotropic process (CIP). After thermally recombining in air at 800 ° C for two hours, the Compacks were sintered in air at 1525 ° C for two hours and then sintered in an argon atmosphere for 15 hours with hot isostatic pressing (HIP) to achieve a transmission at 1530 ° C - Pressurized.

The density of the obtained transparent disc was &gt; 99.9% of the theoretical density. The average tissue particle size (calculated as 1.56 times the measured average fiber length) was 0.61 mu m.

The HV10 Vickers Macro Hardness measured on the polished portion produced by the ceramic technology was HV10 = 14.0 GPa.

In a plane-parallel manner, the disks were polished to a thickness of 4 mm and polished to a surface roughness R _z <0.03 μm on both sides. The actual in-line transmission measured at 640 nm wavelength on these disks was 85.3%. Measurements were made using a gigahertz LCRT-2005-S spectrophotometer.

The total frontal transmittance value was measured at a wavelength of 640 nm from TFT = 86.4% by a Varian Cary spectrometer (Varian Inc., Mulgrave, Victoria, Australia). The haze value (difference between TFT and RIT, divided by TFT, multiplied by 100) determined according to ASTM D 1003-00 from each total transmittance data and in-line transmittance data was 1.3%.

The in-line transmittance of the same disc, measured in the infrared wavelength range at 2000 nm by a spectrometer 400 (Perkin-Elmer, Waltham, Mass., USA) type, was 86.3%.

For the characteristics of visible defect clusters on the size of 20 μm, sample sections of 12 mm x 12 mm size were recorded using a high-resolution scanner. Visual defects were counted for the graph image of this part extended by a factor of 20. Here, a defect concentration of 111 / cm 3 was determined.

Example 3

50 ml of a liquid strontium nitride solution was added to a MgAl ₂ O ₄ suspension of 29.8 mass% spinel powder (S30CR, Baikowski), 69.6 mass% deionized water and 0.6 mass% Dolapix CE64 (Zschimmer & Schwarz) Lt; / RTI &gt; after two hours of anti-agglomeration milling. The concentration of this doping solution was selected so that the content of strontium oxide SrO associated with the mass of the spinel powder was 0.3125 mass%.

With respect to the mass of the spinel powder, drying of the suspension was carried out after the addition of 0.6% by weight of polyvinyl alcohol (Mowiol 4-88, Zschimmer & Schwarz) and 2.0% by weight of glycerol and strong homogenization by means of a stirrer.

The dried screen-granulated packing powder was pre-pressurized for shaping to form circular disks of 30 mm diameter and 9 mm thickness and then pressed again in the cold isotropic process (CIP). After thermally recombining in air at 800 ° C for two hours, Compaq sintered at 1470 ° C for two hours in air and then sintered in an argon atmosphere for 15 hours with hot isostatic pressing (HIP) to achieve permeability at 1470 ° C - Pressurized.

The density of the obtained transparent disc was &gt; 99.9% of the theoretical density. The average tissue particle size (calculated as 1.56 times the measured average fiber length) was 0.36 탆.

The HV10 Vickers Macro Hardness measured on the polished portion produced by the ceramic technique was HV10 = 14.3 GPa.

In a plane-parallel manner, the disks were polished to a thickness of 4 mm and polished to a surface roughness R _z <0.03 μm on both sides. The in-line transmission measured by spectroscopy of the spectral 400 (Perkin-Elmer, Waltham, Mass., USA) type at 2000 nm wavelength on these disks was 86.6%.

For the characteristics of visible defect clusters on a size of 20 mu m, sample portions of 12 mm x 12 mm size were recorded using a high-resolution scanner. Visual defects were counted for the graph image of this part extended by a factor of 20. Here, a defect concentration of 85 / cm &lt; 3 &gt; was determined.

Example 4

To the MgAl ₂ O ₄ suspension of 29.8 mass% spinel powder (S30CR, Baikowski), 50 ml of liquid barium nitride solution was added and 69.6 mass% of deionized water and 0.6 mass% of Dolapix CE64 (Zschimmer & Schwarz) Lt; / RTI &gt; after two hours of anti-agglomeration milling. The concentration of the doping solution was selected so that the content of strontium oxide SrO in relation to the mass of the spinel powder was 0.125 mass%.

With respect to the mass of the spinel powder, drying of the suspension was carried out after the addition of 0.6% by weight of polyvinyl alcohol (Mowiol 4-88, Zschimmer & Schwarz) and 2.0% by weight of glycerol and strong homogenization by means of a stirrer.

The dried screen-granulated packing powder was pre-pressurized for shaping to form circular disks of 30 mm diameter and 9 mm thickness and then pressed again in the cold isotropic process (CIP). After thermally recombining in air at 800 ° C for two hours, Compaq sintered at 1520 ° C for two hours in air and then sintered in an argon atmosphere for 15 hours with hot isostatic pressing (HIP) to achieve a transmission at 1520 ° C - Pressurized.

The density of the obtained transparent disc was &gt; 99.9% of the theoretical density. The average tissue particle size (calculated as 1.56 times the measured average fiber length) was 0.59 mu m.

The HV10 Vickers Macro Hardness measured on the polished portion produced by the ceramic technique was HV10 = 14.1 GPa.

In a plane-parallel manner, the disks were polished to a thickness of 4 mm and polished to a surface roughness R _z <0.03 μm on both sides. The in-line transmittance (RIT) measured at 640 nm wavelength on these disks was 84.5%. Measurements were made by the gigahertz LCRT-2005-S spectrometer, respectively.

By Varian Cary 4000 spectrometer (Varian Inc. Mulgrave, Victoria, Australia), total frontal transmittance values were measured at a wavelength of 640 nm at TFT = 85.5%. From the respective total transmittance data and in-line transmittance data, the haze value (difference between TFT and RIT, divided by TFT, multiplied by 100) determined according to ASTM D 1003-00 was 1.5%.

The in-line transmittance of the same disk, measured in the infrared wavelength range at 2000 nm by a spectrometer 400 (Perkin-Elmer, Waltham, Mass., USA) type, was 86.8%.

For the characteristics of visible defect clusters on a size of 20 mu m, sample portions of 12 mm x 12 mm size were recorded using a high-resolution scanner. Visual defects were counted for the graph image of this part extended by a factor of 20. Here, a defect concentration of 116 / cm &lt; 3 &gt; was determined.

Example 5

To the MgAl ₂ O ₄ suspension of 29.8 mass% spinel powder (S30CR, Baikowski), 50 ml of liquid barium nitride solution was added and 69.6 mass% of deionized water and 0.6 mass% of Dolapix CE64 (Zschimmer & Schwarz) Lt; / RTI &gt; after two hours of anti-agglomeration milling. The concentration of this doping solution was selected so that the content of strontium oxide SrO associated with the mass of the spinel powder was 0.3125 mass%.

With respect to the mass of the spinel powder, drying of the suspension was carried out after the addition of 0.6% by weight of polyvinyl alcohol (Mowiol 4-88, Zschimmer & Schwarz) and 2.0% by weight of glycerol and strong homogenization by means of a stirrer.

The dried screen-granulated packing powder was pre-pressurized for shaping to form circular disks of 30 mm diameter and 9 mm thickness and then pressed again in the cold isotropic process (CIP). After thermally recombining in air at 800 ° C for two hours, Compaq was sintered at 1490 ° C for two hours in air and then sintered in an argon atmosphere for 15 hours with hot isostatic pressing (HIP) to achieve a permeability at 1490 ° C - Pressurized.

The density of the obtained transparent disc was &gt; 99.9% of the theoretical density. The average tissue particle size (calculated as 1.56 times the measured average fiber length) was 0.38 占 퐉.

The HV10 Vickers Macro Hardness measured on the polished portion produced by the ceramic technique was HV10 = 14.3 GPa.

In a plane-parallel manner, the disks were polished to a thickness of 4 mm and polished to a surface roughness R _z <0.03 μm on both sides. The actual in-line transmission measured at 2000 nm wavelength by a spectrometer 400 (Perkin-Elmer, Waltham, Mass., USA) type on these disks was 86.7%.

For the characteristics of visible defect clusters on a size of 20 mu m, sample portions of 12 mm x 12 mm size were recorded using a high-resolution scanner. Visible defects were counted for the graph image of this portion extended by a factor of 20. Here, a defect concentration of 61 / cm &lt; 3 &gt; was determined.

Claims (17)

Or more of oxides of 0.005 to &lt; 0.2 mass% CaO and / or 0.005 to 0.5 mass% SrO and / or 0.005 to &lt; 0.5 mass% BaO, Transparent transparent spinel ceramics in the infrared wavelength range, consisting of sintered magnesium aluminum spinel with a maximum of 0.5% by mass of homogeneously distributed additives of calcium and / or strontium and / or barium. And a concentration of 0.005 to &lt; 0.2 mass% of CaO and / or 0.005 to 0.3 mass% of SrO and / or 0.005 to &lt; 0.25 mass% of BaO, Transparent transparent spinel ceramics in the visible light wavelength range, consisting of sintered magnesium aluminum spinel, having a maximum of 0.3 mass% of homogeneously distributed additives of calcium and / or strontium and / or barium present. 3. The method according to claim 1 or 2,
A transparent spinel ceramic having an average grain size of the sintered magnesium aluminum spinel of <5 μm, preferably <2.5 μm, more preferably <1 μm. The method according to claim 1,
A transparent spinel ceramic in which homogeneously distributed additives are present in a total amount of up to 0.3% by weight. 3. The method of claim 2,
Transparent spinel ceramics in which homogeneously distributed additives are present in a total amount of up to 0.2 mass%. 3. The method according to claim 1 or 2,
Wherein the calcium is present as an additive in a concentration of 0.01 to 0.1% by mass, expressed as CaO. The method according to claim 1,
Strontium and / or barium are present as additive at a concentration expressed by 0.01 to 0.4 mass% SrO and / or 0.01 to 0.4 mass% BaO, SrO and / or BaO, wherein up to 0.3 mass% of strontium and / Or barium additive is present. 3. The method of claim 2,
Strontium and / or barium is present as an additive in a concentration expressed by 0.01-0.2 mass% SrO and / or 0.01-0.15 mass% BaO, SrO and / or BaO, where 0.2 mass% And / or a barium additive is present. The method according to claim 1,
Transparent spinel ceramics with an in-line transmission of> 82%, preferably> 84%, more preferably> 85%, at least in the infrared wavelength range, measured between 1000 nm and 2500 nm at a thickness of ≥3 mm. 3. The method of claim 2,
Transparent spinel ceramics having a RIT of> 80%, preferably> 82%, more preferably> 84%, at least in the range of infrared visible light wavelengths, measured between 600 nm and 650 nm at a thickness of ≥3 mm. 3. The method according to claim 1 or 2,
Transparent spinel ceramics containing no visible defects. 3. The method according to claim 1 or 2,
A transparent spinel ceramic containing visible defects of more than 20 microns at a frequency of < 300 / cm3. 13. The method of claim 12,
A transparent spinel ceramic containing visible defects of more than 20 mu m with a frequency of 50 / cm3 to 150 / cm3. 3. The method according to claim 1 or 2,
≥ 12.5 GPa HV10 clear spinel ceramic with Vickers hardness. A method for producing transparent spinel ceramics according to claim 1,
Soluble compounds containing Ca, Sr and / or Ba and / or compounds dissolved in water containing Ca, Sr and / or Ba and / or organic solvents containing Ca, Sr and / or Ba Or oxides of calcium and / or strontium and / or barium in concentrations of 0.005 to <0.2 mass% CaO and / or 0.005 to <0.5 mass% SrO and / or 0.005 to <0.5 mass% BaO, Wherein a maximum sum of additive contents of 0.5% by mass is carried out to add to the magnesium aluminum spinel powder, the additives are homogeneously distributed, and then the materials are sintered to form a transparent spinel ceramic. A method for producing transparent spinel ceramics according to claim 2,
Soluble compounds containing Ca, Sr and / or Ba and / or compounds dissolved in water containing Ca, Sr and / or Ba and / or organic solvents containing Ca, Sr and / or Ba In the form of compounds, of calcium and / or strontium and / or barium in the concentration expressed as oxides of 0.005 to <0.2 mass% CaO and / or 0.005 to <0.3 mass% SrO and / or 0.005 to <0.25 mass% Wherein a maximum sum of 0.3% by mass of the additive is added to the magnesium aluminum spinel powder, the additives are homogeneously distributed, and then the materials are sintered to form a transparent spinel ceramic. 17. The method according to claim 15 or 16,
The addition of the additive is carried out as part of impregnation or infiltration of the additive into the open pores of the dry ceramic body during slurry preparation or packing of the ceramic, Wherein the solution is realized by ion exchange between a solution comprising Ca, Sr and / or Ba and a wet magnesium aluminum spinel body.