Arsenic-free spinel glass-ceramics with high visible transmission
A transparent glass-ceramic materials contains a spinel solid solution as the main crystalline phase and is free of As 2 O 3 and Sb 2 O 3 . Corresponding precursor alumino-silicate glasses, articles made of said transparent glass-ceramic materials as well as a method for manufacturing such articles, and structures comprising a sheet made of such glass-ceramic materials and electronic or optoelectronic devices comprising such structures are also disclosed. Some materials disclosed can be used as substrates for high temperature growth of high quality monocrystalline or polycrystalline silicon thin films. Structures including such substrates with such thin films thereon can be used in photovoltaic devices, flat panel devices and liquid crystal devices.
1. A transparent glass-ceramic material containing a spinel solid solution as the main crystalline phase, having a coefficient of thermal expansion of 30-40×10 −7 K −1 over a temperature range of 25-300° C. and a composition that is
free of B 2 O 3 , As 2 O 3 and Sb 2 O 3 , with the exception of unavoidable trace thereof, and
comprises SnO 2 , TiO 2 and ZrO 2 , and less than 100 ppm of Fe 2 O 3 ,
wherein the composition, expressed in percentages by weight of oxides, comprises:
0.1-2% of SnO 2 ,
2-4% of TiO 2 , and
3-4.5% of ZrO 2 .
2. The glass-ceramic material according to claim 1 , wherein the composition, expressed in percentages by weight of oxides, essentially consists of:
SiO 2
45-65
Al 2 O 3
14-28
ZnO
4-13
MgO
0-8
with ZnO + MgO
≧8
BaO
0-8
SnO 2
0.1-2
TiO 2
2-4
ZrO 2
3-4.5
Fe 2 O 3
<100 ppm.
3. The glass-ceramic material according to claim 2 , wherein the composition comprises more than 55% by weight of SiO 2 and in that, within said composition, the molar ratio (R 2 O+RO)/Al 2 O 3 is between 0.5 to 1.5, R 2 O being the sum of the moles of alkali oxides, and RO the sum of the moles of alkaline earth oxides plus ZnO.
4. The glass-ceramic material according to claim 1 , wherein the composition, expressed in percentages by weight of oxides, comprises 0.15 to 0.8 wt. % of SnO 2 and/or 2 to 3 wt. % of TiO 2 .
5. The glass-ceramic material according to claim 1 , wherein the composition comprises less than 80 ppm of Fe 2 O 3 .
6. A glass-ceramic article made of a glass-ceramic material according to claim 1 .
7. The article according to claim 6 wherein the article comprises a glass-ceramic sheet.
8. A method for manufacturing a glass-ceramic article according to claim 6 , said method comprising
melting a batch mixture of raw materials able to vitrify to form a molten glass, said batch mixture containing SnO 2 as refining agent,
refining the molten glass to form a refined molten glass,
cooling the refined molten glass and simultaneously forming it into a desired form, and
ceramming the form.
9. The method according to claim 8 , wherein the forming comprises rolling or a float process to produce a sheet.
10. A structure comprising a sheet made of a glass-ceramic according to claim 7 , said structure further comprising at least one layer made of a semiconductor formed on said sheet.
11. An electronic or optoelectronic device comprising a structure according to claim 10 .
12. The device according to claim 11 comprising a photovoltaic device, a flat panel display device or a liquid crystal display device.