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YAG透明陶瓷
YAG透明陶瓷在红外、可见、紫外波段均有很高的透过率，是用作光学窗口的优秀材料，特别是在高温及高能辐射的场合。YAG没有通常光学玻璃等光学材料在2-3μm吸收（由羟基导致），无双折射，各向同性，在很多场合下成为首选光学材料。蓝宝石虽然具有与YAG相似的机械化学稳定性，但因其双折射、各向异性而在很多场合不能使用。
YAG透明陶瓷：透过范围250nm到5000nm，YAG陶瓷莫氏硬度大于YAG晶体（8～8.5），熔点1970oC，折射率1.82(1μm，室温），热导率13W/m·K(室温，是光学玻璃的10倍)，热光系数dn/dt=7.4×10-6℃-1，热胀系数6.9×10-6℃-1。
Undoped YAG Crystal is an excellent material for UV-IR optical windows, particularly for high temperature and high energy density. The mechanical and chemical stability is comparable to sapphire crystal, but YAG is unique with non-birefringence and available with higher optical homogeneity and surface quality.
Main Features:
1) Transmission in 0.25-5.0μm, no absorption in 2-3μm.
2) Extremely hard and durable.
3) High thermal conductivity.
4) High bulk damage threshold.
5) High index of refraction and Non-birefringence.
Basic Properties:
| Crystal structure | Cubic | |
| Density | 4.5g/cm 3 | |
| Transmission Range | 250-5000nm | |
| Melting Point | 1970°C | |
| Specific Heat | 0.59 W.s/g/K | |
| Thermal Conductivity | 14 W/m/K | |
| Thermal Shock Resistance | 790 W/m | |
| Thermal Expansion | 6.9x10 -6 /K | |
| dn/dt, @633nm | 7.3x10 -6 /K -1 | |
| Mohs Hardness | 8.5 | |
| Refractive Index | 1.8245@0.8μm, 1.8197@1.0μm, 1.8121@1.4μm | |
Main Specifications of YAG Windows and Mirrors:
| Orientation | [111] within 5° |
| Diameter | +/-0.1mm |
| Thickness | +/-0.2mm |
| Flatness | better than l /8@633nm |
| Parallelism | better than 30'' |
| Perpendicularity | better than 5' |
| Scratch-Dig | 10-5 per MIL-O-1383A |
| Wavefront Distortion | better than l /2 per inch@1064nm |
As the hardest of oxide crystals, sapphire has a combination of optical and physical properties that make it the best choice for a variety of demanding . Sapphire maintains its strength even at high temperatures. It has good thermal properties, excellent electrical and dielectric properties and is resistant to chemical attack. These properties encourage the use of sapphire in aggressive environments where reliability, optical transmission and strength are requied.
Basic Properties:
| Crystal structure | Hexagonal System | |
| Lattice | a=4.785Å, C=12.991Å | |
| Density | 3.98g/cm3 | |
| Transmission Range | 150-5500nm | |
| Melting Point | 2040°C | |
| Specific Heat | 0.418 W.s/g/K | |
| Thermal Conductivity | 25.12 W/m/K | |
| Thermal Shock Resistance | 790 W/m | |
| Thermal Expansion Coefficient | 5.8x10 -6 /K | |
| dn/dt, @633nm | 13x10 -6 /K | |
| Mohs Hardness | 9 | |
| Refractive Index | 1.83 @0.26μm, 1.76 @0.63μm, 1.58 @5.57μm | |
| Diameter | +/-0.0, -0.1mm |
| Thickness | +/-0.2mm |
| Flatness | better than l per 25 @633nm |
| Parallelism | better than 3' |
| Perpendicularity | better than 5' |
| Scratch-Dig | 80-50 per MIL-O-13830A |
| Wavefront Distortion | less than l /2 per inch( l @1064nm) |