Heat-resistant synthetic jewelry material

#This application is the U.S. national phase of PCT Application No. PCT/RU2013/000538 filed on Jun. 25, 2013, which claims priority to RU Patent Application No. 2013122741 filed on May 13, 2013, the disclosures of which are incorporated in their entirety by reference herein.

#The present invention is related to the production of synthetic materials for jewellery intended for the substitution of natural precious stones.

#Synthetic materials are traditionally used in jewellery for the substitution of natural gemstones. Synthetic gemstones can be divided into two groups. The synthetic gemstones of the first group have the same composition and physical properties as natural precious stones. Among them, there are amethyst, citrine, smoky quartz, alexandrite, ruby and spinel fabricated by Czochralski process, synthetic corundum and spinel manufactured by Verneuil process, hydrothermal emerald.

#TABLE 2 Sample No 1 2 3 Component Concentration (mol %) SiO2 45 54.9 72 Al2O3 30 15 16 MgO 23.9 0.1 4 ZnO 0.1 29 4 Li2O 1 1 4 ZrO2 0.1 10 6 TiO2 15 3 0.1 PbO 0.1 2 7.0 NiO 4 1.0 0.001 CoO 0.001 0.005 3.000 CuO 0.001 0.001 0.001 Cr2O3 0.001 0.001 0.001 Bi2O3 0.001 0.001 0.001 Fe2O3 0.001 0.001 0.001 MnO2 0.001 0.001 0.001 CeO2 0.001 0.001 0.001 Nd2O3 0.001 0.001 0.001 Er2O3 0.001 0.001 0.001 Pr2O3 0.001 0.001 0.001 Au 0.001 0.001 0.001 Heat-treatment conditions 1 stage 660° C., 24 h 800° C., 4 h 770° C., 12 h 2 stage 900° C., 24 h 1000° C., 12 h 1200° C., 1 h Colour Green, Green, Green, transparent opaque opaque Thermal 15.0 19.0 22.0 expansion coefficient (×10−7/° C.) Glass melting 1540 1540 1550 temperature, ° C. Crystalline Solid solution of Solid solution of Solid solution of phases lithium-magnesium- lithium-magnesium- lithium-magnesium- zinc-aluminosilicate zinc-aluminosilicate zinc-aluminosilicate with virgilite (β- with β-spodumene with β-spodumene quartz) structure (keatite) structure (keatite) structure Spinel Spinel Spinel Magnesium Zircon Cordierite aluminotitanates Petalite-like phase Rutile Zirconium titanate Zirconium dioxide Zirconium dioxide Sample No 4 5 6 Component Concentration (mol %) SiO2 45 54.9 70 Al2O3 30 15 18 MgO 12.9 0.1 6 ZnO 0.1 12 3 Li2O 12 18 3 ZrO2 0.1 10 5 TiO2 15 0.1 5 PbO 0.1 2 7.0 NiO 0.001 0.001 0.001 CoO 0.001 0.001 0.001 CuO 4.000 0.050 0.000 Cr2O3 0.001 0.001 0.001 Bi2O3 0.001 0.001 3.000 Fe2O3 0.001 0.001 0.001 MnO2 0.001 0.001 0.001 CeO2 0.001 0.001 0.001 Nd2O3 0.001 0.001 0.001 Er2O3 0.001 0.001 0.001 Pr2O3 0.001 3.000 0.001 Au 0.001 0.001 0.001 Heat-treatment conditions 1 stage 720° C., 6 h 700° C., 12 h 750° C., 1 h 2 stage 1050° C., 24 h 850° C., 12 h 1200° C., 1 h Colour Brown, Bluish-green, Deep-brown, opaque transparent opaque Thermal 18.0 5.0 12.0 expansion coefficient (×10−7/° C.) Glass melting 1520 1520 1550 temperature, ° C. Crystalline Solid solution of Solid solution of Solid solution of phases lithium-magnesium- lithium-magnesium- lithium-magnesium- zinc-aluminosilicate zinc-aluminosilicate zinc-aluminosilicate with β-spodumene with virgilite (β- with β-spodumene (keatite) structure quartz) structure (keatite) structure Sapphirine Spinel Cordierite Enstatite Zirconium titanate Zirconium titanate Magnesium Zirconium dioxide aluminotitanates Sample No 7 8 9 Component Concentration (mol %) SiO2 45 54.9 70 Al2O3 30 15 18 MgO 14.9 0.1 6 ZnO 0.1 20 2 Li2O 10 10 4 ZrO2 0.1 10 5 TiO2 15 3 0.1 PbO 0.1 2 7.0 NiO 0.001 0.001 0.001 CoO 0.001 0.001 0.001 CuO 0.001 0.001 0.001 Cr2O3 1.000 0.001 0.001 Bi2O3 0.001 0.001 0.001 Fe2O3 0.001 3.000 0.001 MnO2 0.001 0.001 0.001 CeO2 0.001 0.100 3.000 Nd2O3 0.001 0.001 0.001 Er2O3 0.001 0.001 0.001 Pr2O3 0.001 0.001 0.001 Au 0.001 0.001 0.001 Heat-treatment conditions 1 stage 680° C., 24 h 800° C., 12 h 780° C., 1 h 2 stage 800° C., 24 h 1100° C., 12 h 1200° C., 1 h Colour Smoky, Light-brown, Brown, transparent opaque opaque Thermal 3.0 10.0 12.0 expansion coefficient (×10−7/° C.) Glass melting 1530 1520 1545 temperature, ° C. Crystalline Solid solution of Solid solution of Solid solution of phases lithium-magnesium- lithium-magnesium- lithium-magnesium- zinc-aluminosilicate zinc-aluminosilicate zinc-aluminosilicate with virgilite (β- with virgilite (β- with virgilite (β- quartz) structure quartz) structure quartz) structure Spinel Willemite Cordierite Magnesium Spinel Zirconium dioxide aluminotitanates Zircon Zirconium titanate Zirconium dioxide Sample No 7 8 9 Component Concentration (mol %) SiO2 45 54.9 70 Al2O3 30 15 18 MgO 10.0 0.1 6 ZnO 0.1 16 3 Li2O 14.9 14 3 ZrO2 0.1 10 5 TiO2 15 3 0.1 PbO 0.1 2 7.0 NiO 0.001 1.0 0.001 CoO 0.001 0.001 0.001 CuO 0.001 0.001 0.001 Cr2O3 0.001 0.001 0.001 Bi2O3 0.001 0.001 0.001 Fe2O3 0.001 0.001 0.001 MnO2 3.000 0.003 0.001 CeO2 0.000 0.000 0.000 Nd2O3 0.001 0.001 0.001 Er2O3 0.001 0.500 3.000 Pr2O3 0.001 0.001 0.001 Au 0.001 0.001 0.001 Heat-treatment conditions 1 stage 680° C., 24 h 780° C., 12 h 800° C., 1 h 2 stage 820° C., 24 h 900° C., 12 h 1200° C., 1 h Colour Light-brown, Rosy, Rosy, transparent transparent opaque Thermal 2.0 5.0 21.0 expansion coefficient (×10−7/° C.) Glass melting 1520 1520 1550 temperature, ° C. Crystalline Solid solution of Solid solution of Solid solution of phases lithium-magnesium- lithium-magnesium- lithium-magnesium- zinc-aluminosilicate zinc-aluminosilicate zinc-aluminosilicate with virgilite (β- with virgilite (β- with β-spodumene quartz) structure quartz) structure (keatite) structure Spinel Spinel Cordierite Magnesium Zirconium titanate Zirconium dioxide aluminotitanates Zirconium dioxide Sample No 4 5 6 Component Concentration (mol %) SiO2 45 54.9 70 Al2O3 30 15 18 MgO 12.9 0.1 6 ZnO 0.1 12 3 Li2O 12 18 3 ZrO2 0.1 10 5 TiO2 15 0.1 5 PbO 0.1 2 7.0 NiO 0.001 0.001 0.001 CoO 0.001 0.001 0.001 CuO 0.001 0.001 0.001 Cr2O3 0.001 0.001 0.001 Bi2O3 0.001 0.001 0.001 Fe2O3 0.001 0.001 0.001 MnO2 0.001 0.001 0.001 CeO2 0.001 0.001 0.001 Nd2O3 0.001 0.001 3.000 Er2O3 0.001 0.001 0.001 Pr2O3 0.001 0.001 0.001 Au 0.003 1.000 0.001 Heat-treatment conditions 1 stage 720° C., 6 h 700° C., 12 h 750° C., 1 h 2 stage 1050° C., 24 h 850° C., 12 h 1200° C., 1 h Colour Purple, Red, Lilac, opaque transparent opaque Thermal 18.0 3.0 12.0 expansion coefficient (×10−7/° C.) Glass melting 1520 1520 1550 temperature, ° C. Crystalline Solid solution of Solid solution of Solid solution of phases lithium-magnesium- lithium-magnesium- lithium-magnesium- zinc-aluminosilicate zinc-aluminosilicate zinc-aluminosilicate with β-spodumene with virgilite (β- with β-spodumene (keatite) structure quartz) structure (keatite) structure Sapphirine Spinel Cordierite Enstatite Zirconium titanate Zirconium dioxide Magnesium Zirconium dioxide aluminotitanates

#Introduction of SiO2 in an amount less than suggested does not lead to the formation of transparent material during glass melting, and the introduction of SiO2 in an amount greater than suggested increases the melting temperature of the melt to temperatures exceeding 1600° C., thus no standard glass-making equipment can be used for glass melting. It impedes obtaining the pure glass melt. Introduction of Li2O in an amount smaller and larger than the concentration range claimed prevents the obtaining of solid solutions of lithium-magnesium-zinc-aluminosilicate with virgilite (β-quartz) or keatite structure, lowering the CTE of the material obtained. Introduction of Al2O3, MgO, ZnO and Li2O in an amount smaller and larger than the concentration range claimed, prevents the obtaining of transparent initial glass. Introduction of PbO in amounts less than suggested, does not lead to increasing refractive index of the material. Introduction of PbO in an amount larger than the concentration range claimed prevents the obtaining of transparent initial glass. Introduction of TiO2 and ZrO2 in an amount less than claimed prevents obtaining the solid monolithic material after the secondary heat-treatment. Introduction of TiO2 and ZrO2 in an amount greater than claimed leads to crystallization of the glass melt during casting. Introduction of the colouring agents NiO, CoO, CuO, Cr2O3, Bi2O3, Fe2O3, MnO2, CeO2, Nd2O3, Er2O3, Pr2O3 and Au in an amount less than claimed does not lead to material colouration. Introduction of NiO, CoO, CuO, Cr2O3, Bi2O3, Fe2O3, MnO2, CeO2, Nd2O3, Er2O3, Pr2O3 and Au in an amount greater than claimed leads to crystallization of the glass melt during casting.

#Additional heat-treatment of the glass at the first stage at below 660° C. does not lead to liquid phase-separation and crystallization of titanium- and zirconium-containing phases, ensuring nanoscale crystallization of the initial glass. Additional heat-treatment of the glass at the first stage at above 800° C. leads to crystallization of large-size silicate crystals that damages the integrity of samples. The duration of the heat-treatment at the first stage which is less than 1 hour does not result in the phase separation of the initial glass, which damages the integrity of the samples after the heat treatment at the second stage. The duration of the heat treatment on the first stage which is more than 24 hours results in crystallization of undesired crystalline phases and therefore does not result in the desired colouration.