WO2003091174A1 - Production of optical glass precursors in powder form containing nanocrystals - Google Patents

Production of optical glass precursors in powder form containing nanocrystals Download PDF

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Publication number
WO2003091174A1
WO2003091174A1 PCT/CA2003/000590 CA0300590W WO03091174A1 WO 2003091174 A1 WO2003091174 A1 WO 2003091174A1 CA 0300590 W CA0300590 W CA 0300590W WO 03091174 A1 WO03091174 A1 WO 03091174A1
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fluoride
glass
doped
rare earth
optically active
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PCT/CA2003/000590
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French (fr)
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Sabin Boily
Pascal Tessier
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Groupe Minutia Inc.
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Priority to AU2003221656A priority Critical patent/AU2003221656A1/en
Publication of WO2003091174A1 publication Critical patent/WO2003091174A1/en

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    • 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
    • C03C1/00—Ingredients generally applicable to manufacture of glasses, glazes, or vitreous enamels
    • C03C1/02—Pretreated ingredients
    • 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
    • C03C14/00—Glass compositions containing a non-glass component, e.g. compositions containing fibres, filaments, whiskers, platelets, or the like, dispersed in a glass matrix
    • C03C14/006—Glass compositions containing a non-glass component, e.g. compositions containing fibres, filaments, whiskers, platelets, or the like, dispersed in a glass matrix the non-glass component being in the form of microcrystallites, e.g. of optically or electrically active material
    • 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
    • C03C2214/00—Nature of the non-vitreous component
    • C03C2214/30—Methods of making the composites

Definitions

  • the present invention pertains to improvements in the field of optical glass materials. More particularly, the invention relates to a method of producing an optical glass precursor containing nanocrystals.
  • Nanocrystals embedded in optical glass materials have unique and interesting properties which render these materials suitable for use in the development of optical communication infrastructure. For example, room temperature light emission by silicon nanocrystals embedded in a silica matrix has been observed. Rare earth doped-fibers are used for the amplification of optical signals on communication channels. The properties of such amplifiers are greatly improved by using glass-ceramic fibers containing rare earth-doped nanocrystals.
  • the level of chromium is limited since it depends on the diffusion of chromium at this temperature and during the time the glass is heated.
  • the final composition of the nanocrystals is thus dictated by the composition of the glass and nanocrystals of different composition cannot be introduced into the glass matrix.
  • a Ge0 2 -Si0 2 gel glass is first prepared by a sol- gel method through hydrolysis of Si(OC 2 H 5 ) 4 and Cl 3 -Ge-C 2 H 4 -C00H to form a gel and heating of the gel at 600°C for 10 hours to form the desired gel glass. The latter is further heated for 10 hours at 500-700°C in a hydrogen gas atmosphere to reduce Ge 4+ ions and thereby precipitate cubic Ge nanocrystals. Such a process is not only lengthy, but also does not permit doping of the Ge nanocrystals.
  • Ion implantation has been used to produce Er-doped silicon nanocrystals in a 300 run thick silica layer grown on a silicon substrate, as described by G. Franzo et al. in Nuclear Instruments and Methods in Physics Research B, Vol. 175-177, 2001, pp. 140-147.
  • ion implantation is a sophisticated and costly method that is scarcely used for large-scale fabrication.
  • a method of producing an optical glass precursor in powder form containing nanocrystals comprises subjecting a glass material and an optically active crystalline material to high-energy ball milling to obtain a composite material in powder form comprising particles each containing nanocrystals of the optically active crystalline material uniformly dispersed in a matrix of the glass material, the composite material defining the aforesaid optical glass precursor.
  • nanocrystals refers to a crystal having a size of 100 nanometers or less.
  • high-energy ball milling refers to a ball milling process capable of forming the aforesaid particles comprising nanocrystals within a period of time of about 40 hours. The high-energy ball milling is generally carried out for a period of time ranging from about 1 to 10 hours. Because the nanocrystals are not formed by thermal treatment of the glass material, but rather formed mechanically during the mechanical mixing of the optically active crystalline material with the glass material through high-energy ball milling, one can chose the optically active material and the glass material with practically no consideration for thermodynamic parameters.
  • glass material refers to an amorphous material which can be either an oxide glass, such as silica or silica combined with another element to form a silicate, or a fluoride glass.
  • oxide glasses include silica glass, alumino-silicate glass, boro-silicate glass and germano-silicate glass. Silica glass and germano-silicate glass are preferred.
  • fluoride glasses examples include glasses made from zirconium tetrafluoride (ZrF ), barium difluoride (BaF 2 ), lanthanum trifluoride (LaF 3 ), aluminum trifluoride (A1F 3 ) and sodium fluoride (NaF).
  • ZrF zirconium tetrafluoride
  • BaF 2 barium difluoride
  • LaF 3 lanthanum trifluoride
  • Al aluminum trifluoride
  • NaF sodium fluoride
  • optically active crystalline material refers to a crystalline substance which, when subjected to illumination by electromagnetic radiation such as light, either amplifies this radiation or emits electromagnetic radiation of a wavelength different than that of the incoming radiation, or selectively absorbs incoming electromagnetic radiation of a specific wavelength.
  • the optically active crystalline material can be a rare earth-containing fluoride, a rare earth- doped oxide or a transition metal-doped oxide.
  • rare earth-containing fluorides include rare earth fluorides such as dysprosium fluoride, erbium fluoride, europium fluoride, neodymium fluoride, praseodymium fluoride and yttrium fluoride, and solid solutions of a rare earth metal in an alkali or alkaline earth fluoride, such as a solid solution of erbium in calcium fluoride.
  • rare earth-doped oxides include erbium-doped yttrium aluminum garnet, neodymium-doped yttrium aluminum garnet, praseodymium-doped yttrium aluminum garnet, europium- doped stannic oxide and europium-doped yttrium oxide.
  • transition metal-doped oxides include titanium-doped alumina, nickel-doped yttrium aluminum garnet, iron-doped lithium niobium oxide, chromium-doped forsterite, chromium-doped magnesium aluminate spinel and cobalt-doped magnesium aluminate spinel.
  • the optically active crystalline material can also be a semi-conductive material such as silicon, germanium, gallium arsenide or barium titanate.
  • the high-energy ball milling is carried out in a vibratory ball mill operated at a frequency of 8 to 25 Hz, preferably about 17 Hz. It is also possible to carry out such a ball milling in a rotary ball mill operated at a speed of 100 to 2000 r.p.m., preferably about lOOO r.p.m..
  • the particles obtained generally have an average particle size of 0.1 to 100 ⁇ m.
  • the high-energy ball milling is carried out under an inert gas atmosphere such as a gas atmosphere comprising argon or helium. An atmosphere of argon is preferred.
  • the high-energy ball milling under a reactive gas atmosphere such as air or a gas atmosphere comprising hydrogen, oxygen or fluorine.
  • a reactive gas atmosphere such as air or a gas atmosphere comprising hydrogen, oxygen or fluorine.
  • the optically active crystalline material comprises germanium
  • the high-energy ball milling is carried out in the presence of a lubricating agent so as to reduce agglomeration and help subsequent densification.
  • a lubricating agent include stearic acid, acetone, ethanol, isopropanol, methanol, toluene and water.
  • Stearic acid is preferred.
  • the optical glass precursor in powder form produced according to the invention can be used to form dense optical glass bodies by powder metallurgy.
  • powder metallurgy refers to a technique in which the bulk powders are transformed into preforms of a desired shape by compaction or shaping followed by a sintering step.
  • Compaction refers to techniques where pressure is applied to the powder, as, for example, cold uniaxial pressing, cold isostatic pressing or hot isostatic pressing.
  • Shaping refers to techniques executed without the application of external pressure such as powder filing or slurry casting.
  • the densification process ensures the transparency of the glass matrix.
  • the preforms thus obtained can be used for the manufacture of optical fibers.
  • the optical glass precursor in powder form produced according to the invention can also be used to form thin films by physical or thermal deposition techniques.
  • thermal deposition refers to a technique in which powder particles are injected in a torch and sprayed on a conductive substrate such as graphite or copper, to form thereon a highly dense coating. The particles acquire a high velocity and are partially or totally melted during the flight path. The coating is built by the solidification of the droplets on the substrate surface. Examples of such techniques include plasma spray, arc spray and high velocity oxy-fuel. The films produced in this manner can be used as filters.
  • the deposition techniques can be used to fabricate a preform having a composition gradient by depositing gradually varying amounts of powders of different composition on a rotating substrate.
  • the preform thus obtained can be used to produce the desired optical fibers.
  • An optical glass precursor in powder form comprising a germano-silicate glass matrix and nanocrystals of Ca 0.9 Er 0. ⁇ F 2 was prepared starting from SiO 2 (50%)-GeO 2 (50%) glass and a crystalline Ca 0.9 Er 0 1 F 2 solid solution in powder form.
  • the Ca 0.9 Er 0 . ⁇ F 2 powder was prepared by the method described in Solid State Ionics, Vol. 122, 1999, pp. 255-262.
  • An optical glass precursor in powder form comprising a germano-silicate glass matrix and nanocrystals of titanium-doped alumina was prepared starting from SiO 2 (50%)-GeO (50%) glass and a crystalline titanium-doped alumina of formula Alj 8 Ti 0 . 2 O 3 in powder form.
  • the Al ⁇ .8 Ti 0.2 O 3 powder was prepared by ball milling 0.9 g of A1 0 3 and 0.1 g of Ti 2 0 3 in a silicon nitride crucible for 10 hours with a ball-to-powder mass ratio of 8: 1 using a SPEX 8000 vibratory ball mill operated at 17 Hz. The operation was carried out under atmospheric air, the crucible being closed and sealed with a rubber gasket.
  • An optical glass precursor in powder form comprising a silica glass matrix and nanocrystals of titanium- doped alumina was prepared starting from Si0 2 glass and a crystalline titanium-doped alumina of formula Al1.sTio .2 O 3 in powder form.
  • the Si0 2 glass used was a commercially available silica glass powder.
  • the Al 1 8 Ti 02 O 3 powder was prepared by ball milling 0.9 g of A1 2 0 3 and 0.1 g of Ti 2 0 3 in a silicon nitride crucible for 10 hours with a ball-to-powder mass ratio of 8: 1 using a SPEX 8000 vibratory ball mill operated at 17 Hz. The operation was carried out under atmospheric air, the crucible being closed and sealed with a rubber gasket.
  • EXAMPLE 4 An optical glass precursor in powder form comprising a fluoride glass matrix and nanocrystals of Cao. 9 Ero .1 F 2 was prepared starting from a fluoride glass comprising 53 mole% of ZrF , 20 mole% of BaF 2 , 4 mole% of LaF 3 , 3 mole% of A1F 3 and 20 mole% of NaF, and a crystalline Cao.c1Ero.iF 2 solid solution in powder form. The fluoride glass made by conventional melting techniques was crushed into small pieces. The Cao .9 Ero . ⁇ F 2 powder was prepared by the method described in Solid State Ionics, Vol. 122, 1999, pp. 255-262.
  • 0.94 g of the above fluoride glass and 0.06 g of the above fluoride powder were ball milled in a silicon nitride crucible with a ball-to- powder mass ratio of 8:1 using a SPEX 8000 vibratory ball mill operated at a frequency of about 17 Hz. The operation was performed under a controlled argon atmosphere. The crucible was closed and sealed with a rubber gasket. After 5 hours of high-energy ball milling, a composite material in powder form was obtained, the composite material comprising nanocrystals of Cao. 9 Er 0 1 F 2 embedded in a matrix of the fluoride glass.

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  • Life Sciences & Earth Sciences (AREA)
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Abstract

The invention relates to a method of producing an optical glass precursor in powder form containing nanocrystals. The method of the invention comprises subjecting a glass material and an optically active crystalline material to high-energy ball milling to obtain a composite material in powder form comprising particles each containing nanocrystals of the optically active crystalline material uniformly dispersed in a matrix of the glass material, the composite material defining the aforesaid optical glass precursor. Such a method enables the composition of the nanocrystals to be varied independently of the composition of the glass matrix.

Description

PRODUCTION OF OPTICAL GLASS PRECURSORS IN POWDER FORM CONTAINING NANOCRYSTALS
Technical Field The present invention pertains to improvements in the field of optical glass materials. More particularly, the invention relates to a method of producing an optical glass precursor containing nanocrystals. Background Art
Nanocrystals embedded in optical glass materials have unique and interesting properties which render these materials suitable for use in the development of optical communication infrastructure. For example, room temperature light emission by silicon nanocrystals embedded in a silica matrix has been observed. Rare earth doped-fibers are used for the amplification of optical signals on communication channels. The properties of such amplifiers are greatly improved by using glass-ceramic fibers containing rare earth-doped nanocrystals.
Known methods of producing optical glass containing nanocrystals are usually unpractical or costly. Moreover, they do not permit much flexibility in terms of composition of the nanocrystals and usually do not allow embedding more than one type of nanocrystals in the glass matrix. The most common method is the partial crystallization of glass by heat treatment. Such a procedure is described by F. Rossi et al. in Optical Materials, Vol. 13, 2000, pp. 373-379. Nucleation of magnesium aluminate spinel nanocrystals is obtained by heating cordierite glass at 950°C for 10 minutes. Some of the chromium present in the initial cordierite glass is found in the nanocrystals. The level of chromium is limited since it depends on the diffusion of chromium at this temperature and during the time the glass is heated. The final composition of the nanocrystals is thus dictated by the composition of the glass and nanocrystals of different composition cannot be introduced into the glass matrix.
H. Gang et al. in Journal of Crystal Growth, Vol. 236, 2002, pp. 373-375 have described the preparation of Si02 glasses containing germanium nanocrystals. A Ge02-Si02 gel glass is first prepared by a sol- gel method through hydrolysis of Si(OC2H5)4 and Cl3-Ge-C2H4-C00H to form a gel and heating of the gel at 600°C for 10 hours to form the desired gel glass. The latter is further heated for 10 hours at 500-700°C in a hydrogen gas atmosphere to reduce Ge4+ ions and thereby precipitate cubic Ge nanocrystals. Such a process is not only lengthy, but also does not permit doping of the Ge nanocrystals.
Ion implantation has been used to produce Er-doped silicon nanocrystals in a 300 run thick silica layer grown on a silicon substrate, as described by G. Franzo et al. in Nuclear Instruments and Methods in Physics Research B, Vol. 175-177, 2001, pp. 140-147. However, ion implantation is a sophisticated and costly method that is scarcely used for large-scale fabrication.
The shortcomings of the existing methods are thus either their cost, the high temperatures or lengthy procedures involved, or the limits they pose on the composition of the nanocrystals to be embedded in the glass matrix. Disclosure of the Invention
It is therefore an object of the present invention to overcome the above drawbacks and to provide an easy and low-cost method of producing an optical glass precursor containing nanocrystals, enabling the composition of the nanocrystals to be varied independently of the composition of the glass matrix.
In accordance with the present invention, there is provided a method of producing an optical glass precursor in powder form containing nanocrystals. The method of the invention comprises subjecting a glass material and an optically active crystalline material to high-energy ball milling to obtain a composite material in powder form comprising particles each containing nanocrystals of the optically active crystalline material uniformly dispersed in a matrix of the glass material, the composite material defining the aforesaid optical glass precursor.
The term "nanocrystals" as used herein refers to a crystal having a size of 100 nanometers or less. The expression "high-energy ball milling", on the other hand, refers to a ball milling process capable of forming the aforesaid particles comprising nanocrystals within a period of time of about 40 hours. The high-energy ball milling is generally carried out for a period of time ranging from about 1 to 10 hours. Because the nanocrystals are not formed by thermal treatment of the glass material, but rather formed mechanically during the mechanical mixing of the optically active crystalline material with the glass material through high-energy ball milling, one can chose the optically active material and the glass material with practically no consideration for thermodynamic parameters. Moreover, high-energy ball milling is an inherently low cost process compared to other methods such as ion implantation. The term "glass material" as used herein refers to an amorphous material which can be either an oxide glass, such as silica or silica combined with another element to form a silicate, or a fluoride glass. Examples of suitable oxide glasses include silica glass, alumino-silicate glass, boro-silicate glass and germano-silicate glass. Silica glass and germano-silicate glass are preferred. Examples of fluoride glasses, on the other hand, include glasses made from zirconium tetrafluoride (ZrF ), barium difluoride (BaF2), lanthanum trifluoride (LaF3), aluminum trifluoride (A1F3) and sodium fluoride (NaF). The expression "optically active crystalline material" as used herein refers to a crystalline substance which, when subjected to illumination by electromagnetic radiation such as light, either amplifies this radiation or emits electromagnetic radiation of a wavelength different than that of the incoming radiation, or selectively absorbs incoming electromagnetic radiation of a specific wavelength. The optically active crystalline material can be a rare earth-containing fluoride, a rare earth- doped oxide or a transition metal-doped oxide. Examples of rare earth- containing fluorides include rare earth fluorides such as dysprosium fluoride, erbium fluoride, europium fluoride, neodymium fluoride, praseodymium fluoride and yttrium fluoride, and solid solutions of a rare earth metal in an alkali or alkaline earth fluoride, such as a solid solution of erbium in calcium fluoride. Examples of rare earth-doped oxides include erbium-doped yttrium aluminum garnet, neodymium-doped yttrium aluminum garnet, praseodymium-doped yttrium aluminum garnet, europium- doped stannic oxide and europium-doped yttrium oxide. Examples of transition metal-doped oxides, on the other hand, include titanium-doped alumina, nickel-doped yttrium aluminum garnet, iron-doped lithium niobium oxide, chromium-doped forsterite, chromium-doped magnesium aluminate spinel and cobalt-doped magnesium aluminate spinel. The optically active crystalline material can also be a semi-conductive material such as silicon, germanium, gallium arsenide or barium titanate. Modes for Carrying out the Invention
According to a preferred embodiment of the invention, the high-energy ball milling is carried out in a vibratory ball mill operated at a frequency of 8 to 25 Hz, preferably about 17 Hz. It is also possible to carry out such a ball milling in a rotary ball mill operated at a speed of 100 to 2000 r.p.m., preferably about lOOO r.p.m.. The particles obtained generally have an average particle size of 0.1 to 100 μm. According to another preferred embodiment, the high-energy ball milling is carried out under an inert gas atmosphere such as a gas atmosphere comprising argon or helium. An atmosphere of argon is preferred. In some cases, it is also possible to carry out the high-energy ball milling under a reactive gas atmosphere such as air or a gas atmosphere comprising hydrogen, oxygen or fluorine. For example, in the case where the optically active crystalline material comprises germanium, it is preferable to carry out the high-energy ball milling under a gas atmosphere comprising a reducing gas such as hydrogen so as to lower the reactivity of germanium with oxygen and thus prevent the germanium from undergoing oxidation.
According to a further preferred embodiment, the high-energy ball milling is carried out in the presence of a lubricating agent so as to reduce agglomeration and help subsequent densification. Examples of suitable lubricating agents include stearic acid, acetone, ethanol, isopropanol, methanol, toluene and water. Stearic acid is preferred.
The optical glass precursor in powder form produced according to the invention can be used to form dense optical glass bodies by powder metallurgy. The expression "powder metallurgy" as used herein refers to a technique in which the bulk powders are transformed into preforms of a desired shape by compaction or shaping followed by a sintering step. Compaction refers to techniques where pressure is applied to the powder, as, for example, cold uniaxial pressing, cold isostatic pressing or hot isostatic pressing. Shaping refers to techniques executed without the application of external pressure such as powder filing or slurry casting. The densification process ensures the transparency of the glass matrix. The preforms thus obtained can be used for the manufacture of optical fibers. They can also be used for producing functional optical elements such as a gain medium for a laser or a fiber amplifier, or an upconversion device. The optical glass precursor in powder form produced according to the invention can also be used to form thin films by physical or thermal deposition techniques. The expression "thermal deposition" as used herein refers to a technique in which powder particles are injected in a torch and sprayed on a conductive substrate such as graphite or copper, to form thereon a highly dense coating. The particles acquire a high velocity and are partially or totally melted during the flight path. The coating is built by the solidification of the droplets on the substrate surface. Examples of such techniques include plasma spray, arc spray and high velocity oxy-fuel. The films produced in this manner can be used as filters.
Since it is often desirable to produce optical fibers with a gradually varying composition from core to cladding, the deposition techniques can be used to fabricate a preform having a composition gradient by depositing gradually varying amounts of powders of different composition on a rotating substrate. The preform thus obtained can be used to produce the desired optical fibers.
The following non-limiting examples illustrate the invention. EXAMPLE 1
An optical glass precursor in powder form comprising a germano-silicate glass matrix and nanocrystals of Ca0.9Er0.ιF2 was prepared starting from SiO2(50%)-GeO2(50%) glass and a crystalline Ca0.9Er0 1F2 solid solution in powder form. The SiO2(50%)-GeO2(50%) glass made by conventional melting techniques was crushed into small pieces. The Ca0.9Er0.ιF2 powder was prepared by the method described in Solid State Ionics, Vol. 122, 1999, pp. 255-262.
0.94 g of the above germano-silicate glass and 0.06 g of the above fluoride powder were ball milled in a silicon nitride crucible with a ball-to-powder mass ratio of 8: 1 using a SPEX 8000 (trademark) vibratory ball mill operated at a frequency of about 17 Hz. The operation was performed under a controlled argon atmosphere. The crucible was closed and sealed with a rubber gasket. After 5 hours of high-energy ball milling, a composite material in powder form was obtained, the composite material comprising nanocrystals of Cao.9Ero.ιF2 embedded in a matrix of the germano-silicate glass. EXAMPLE 2
An optical glass precursor in powder form comprising a germano-silicate glass matrix and nanocrystals of titanium-doped alumina was prepared starting from SiO2(50%)-GeO (50%) glass and a crystalline titanium-doped alumina of formula Alj 8Ti0.2O3 in powder form. The SiO2(50%)- GeO2(50%) glass made by conventional melting techniques was crushed into small pieces. The Alι.8Ti0.2O3 powder was prepared by ball milling 0.9 g of A1 03 and 0.1 g of Ti203 in a silicon nitride crucible for 10 hours with a ball-to-powder mass ratio of 8: 1 using a SPEX 8000 vibratory ball mill operated at 17 Hz. The operation was carried out under atmospheric air, the crucible being closed and sealed with a rubber gasket.
3.76 g of the above germano-silicate glass and 0.24 g of the above titanium-doped alumina powder were ball milled in a silicon nitride crucible with a ball-to-powder mass ratio of 2:1 using a SPEX 8000 vibratory ball mill operated at 17 Hz. The operation was carried out under a controlled oxygen atmosphere. The crucible was closed and sealed with a rubber gasket. After 5 hours of high-energy ball milling, a composite material in powder form was obtained, the composite material comprising nanocrystals of titanium-doped alumina embedded in a matrix of the germano-silicate glass. EXAMPLE 3
An optical glass precursor in powder form comprising a silica glass matrix and nanocrystals of titanium- doped alumina was prepared starting from Si02 glass and a crystalline titanium-doped alumina of formula Al1.sTio.2O3 in powder form. The Si02 glass used was a commercially available silica glass powder. The Al1 8Ti02O3 powder was prepared by ball milling 0.9 g of A1203 and 0.1 g of Ti203 in a silicon nitride crucible for 10 hours with a ball-to-powder mass ratio of 8: 1 using a SPEX 8000 vibratory ball mill operated at 17 Hz. The operation was carried out under atmospheric air, the crucible being closed and sealed with a rubber gasket.
3.76 g of the above silica glass powder and 0.24 g of the above titanium-doped alumina powder were ball milled in a silicon nitride crucible with a ball-to-powder mass ratio of 2: 1 using a SPEX 8000 vibratory ball mill operated at 17 Hz. The operation was carried out under atmospheric air, the crucible was closed and sealed with a rubber gasket. After 5 hours of high-energy ball milling, a composite material in powder form was obtained, the composite material comprising nanocrystals of titanium-doped alumina embedded in a matrix of the silica glass. The crucible was opened, filled with methanol and closed again, and the composite material in powder form was milled for an additional period of 5 minutes, after which period the methanol was evaporated. EXAMPLE 4 An optical glass precursor in powder form comprising a fluoride glass matrix and nanocrystals of Cao.9Ero.1F2 was prepared starting from a fluoride glass comprising 53 mole% of ZrF , 20 mole% of BaF2, 4 mole% of LaF3, 3 mole% of A1F3 and 20 mole% of NaF, and a crystalline Cao.c1Ero.iF2 solid solution in powder form. The fluoride glass made by conventional melting techniques was crushed into small pieces. The Cao.9Ero.ιF2 powder was prepared by the method described in Solid State Ionics, Vol. 122, 1999, pp. 255-262.
0.94 g of the above fluoride glass and 0.06 g of the above fluoride powder were ball milled in a silicon nitride crucible with a ball-to- powder mass ratio of 8:1 using a SPEX 8000 vibratory ball mill operated at a frequency of about 17 Hz. The operation was performed under a controlled argon atmosphere. The crucible was closed and sealed with a rubber gasket. After 5 hours of high-energy ball milling, a composite material in powder form was obtained, the composite material comprising nanocrystals of Cao.9Er0 1F2 embedded in a matrix of the fluoride glass.

Claims

1. A method of producing an optical glass precursor in powder form containing nanocrystals, which comprises subjecting a glass material and an optically active crystalline material to high-energy ball milling to obtain a composite material in powder form comprising particles each containing nanocrystals of said optically active crystalline material uniformly dispersed in a matrix of said glass material, said composite material defining said optical glass precursor.
2. A method according to claim 1, wherein said glass material is selected from the group consisting of oxide glasses and fluoride glasses.
3. A method according to claim 2, wherein said glass material is an oxide glass selected from the group consisting of silica glass, alumino- silicate glass, boro-silicate glass and germano-silicate glass.
4. A method according to claim 3, wherein said glass material is silica glass.
5. A method according to claim 3, wherein said glass material is germano-silicate glass.
6. A method according to claim 2, wherein said glass material is a fluoride glass made from zirconium tetrafluoride, barium difluoride, lanthanum trifluoride, aluminum trifluoride and sodium fluoride.
7. A method according to claim 1, wherein said optically active crystalline material is selected from the group consisting of rare earth- containing fluorides, rare earth-doped oxides, transition metal-doped oxides and semi-conductive materials.
8. A method according to claim 7, wherein said optically active crystalline material is a rare earth-containing fluoride selected from the group consisting of rare earth fluorides and solid solutions of a rare earth metal in an alkali or alkaline earth fluoride.
9. A method according to claim 8, wherein said rare earth- containing fluoride is a rare earth fluoride selected from the group consisting of dysprosium fluoride, erbium fluoride, europium fluoride, neodymium fluoride, praseodymium fluoride and yttrium fluoride.
10. A method according to claim 8, wherein said rare earth- containing fluoride is a solid solution of erbium in calcium fluoride.
11. A method according to claim 10, wherein said solid solution of erbium in calcium fluoride has the formula Ca0.9Er0 1F2.
12. A method according to claim 7, wherein said optically active crystalline material is a rare earth-doped oxide selected from the group consisting of erbium-doped yttrium aluminum garnet, neodymium-doped yttrium aluminum garnet, praseodymium-doped yttrium aluminum garnet, europium-doped stannic oxide and europium-doped yttrium oxide.
13. A method according to claim 7, wherein said optically active crystalline material is a transition metal-doped oxide selected from the group consisting of titanium-doped alumina, nickel-doped yttrium aluminum garnet, iron-doped lithium niobium oxide, chromium-doped forsterite, chromium-doped magnesium aluminate spinel and cobalt-doped magnesium aluminate spinel.
14. A method according to claim 13, wherein said transition metal-doped oxide is a titanium-doped alumina of formula Al1.gTio.2O3.
15. A method according to claim 7, wherein said optically active crystalline material is a semi-conductive material selected from the group consisting of silicon, germanium, gallium arsenide and barium titanate.
16. A method according to claim 1, wherein said glass material is silica glass and said optically active crystalline material is a transition metal-doped oxide.
17. A method according to claim 16, wherein said transition metal-doped oxide is a titanium-doped alumina of formula Al1.gTio.2O3.
18. A method according to claim 1, wherein said glass material is germano-silicate glass and said optically active crystalline material is a transition metal-doped oxide.
19. A method according to claim 18, wherein said transition metal-doped oxide is titanium-doped alumina.
20. A method according to claim 1, wherein said glass material is germano-silicate glass and said optically active crystalline material is a rare earth-containing fluoride.
21. A method according to claim 20, wherein said rare earth- containing fluoride is selected from the group consisting of rare earth fluorides and solid solutions of a rare earth metal in an alkali or alkaline earth fluoride.
22. A method according to claim 21, wherein said rare earth- containing fluoride is a solid solution of erbium in calcium fluoride.
23. A method according to claim 22, wherein said solid solution of erbium in calcium fluoride has the formula Cao.9Ero.1F2.
24. A method according to claim 1, wherein said glass material is a fluoride glass and said optically active crystalline material is a rare earth- containing fluoride.
25. A method according to claim 24, wherein said fluoride glass is made from zirconium tetrafluoride, barium difluoride, lanthanum trifluoride, aluminum trifluoride and sodium fluoride.
26. A method according to claim 24, wherein said rare earth- containing fluoride is selected from the group consisting of rare earth fluorides and solid solutions of a rare earth metal in an alkali or alkaline earth fluoride.
27. A method according to claim 26, wherein said rare earth- containing fluoride is a solid solution of erbium in calcium fluoride.
28. A method according to claim 27, wherein said solid solution of erbium in calcium fluoride has the formula Cao.9Ero.jF2.
29. A method according to claim 1, wherein said high-energy ball milling is carried in a vibratory ball mill operated at a frequency of 5 to 40 Hz.
30. A method according to claim 29, wherein said vibratory ball mill is operated at a frequency of about 17 Hz.
31. A method according to claim 1 , wherein said high-energy ball milling is carried out in a rotary ball mill operated at a speed of 100 to 2000 r.p.m.
32. A method according to claim 31, wherein said rotary ball mill is operated at a speed of about 1000 r.p.m.
33. A method according to claim 1, wherein said high-energy ball milling is carried out under an inert gas atmosphere.
34. A method according to claim 33, wherein said inert gas atmosphere comprises argon.
35. A method according to claim 1, wherein said high-energy ball milling is carried out under a reactive gas atmosphere.
36. A method according to claim 35, wherein said optically active crystalline material comprises germanium and wherein said reactive gas atmosphere comprises hydrogen.
37. A method according to claim 1, wherein said high-energy ball milling is carried out in the presence of a lubricating agent.
38. A method according to claim 37, wherein said lubricating agent is selected from the group consisting of stearic acid, acetone, ethanol, isopropanol, methanol, toluene and water.
39. A method according to claim 38, wherein said lubricating agent is stearic acid.
40. A method according to claim 1, wherein said high-energy ball milling is carried out for a period of time ranging from about 1 to 10 hours.
41. A method according to claim 40, wherein said high-energy ball milling is carried out for a period of time of about 5 hours.
42. A method according to claim 1, wherein said particles have an average particle size of 0.1 to 100 μm.
PCT/CA2003/000590 2002-04-24 2003-04-24 Production of optical glass precursors in powder form containing nanocrystals WO2003091174A1 (en)

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