Chemical and Physical Properties of Sapphire
Chemical formula	99.99% （Al2O3）
Crystal Structure	Hexagonal structure
Lattice constants	a=4.785Å, c=12.991Å
Density	3.98g/cm3
Hardness	9
Tensile strength	0.4GPa@25℃, 0.35GPa@1000℃
Compressive srength	2 1GPa@25℃
Flexural strength	0.6GPa@25℃
Young's modulus	350GPa@25℃
Compressive modulus	380GPa@25℃
Flexural modulus	360GPa@25℃
Rigidity modulus	150GPa@25℃
Bulk modulus	240GPa@25℃
Poisson's ratio	0.29

What is the transmission spectrum of sapphire glass windows?
Sapphire offers a broad transmission range from UV to mid infrared wavelengths (250 – 5000 nm). It is one of hardest oxide crystal, most durable and scratch resistant materials.

What is the wavelength of a sapphire window?
Sapphire is optically transparent from UV 150 nm up to MIR 5 um, so an uncoated sapphire window will prevent any fluorescence effects.

Highly Recommended Sapphire Windows from Yutai Optics:
Optical Sapphire Windows
Sapphire Windows with Hole
Thin Sapphire Glass Sheet
Rectangular Sapphire Windows with Round Corners