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Sapphire application

Basic structure of sapphire：
The composition of sapphire is alumina (Al2O3), which is composed of three oxygen atoms and two aluminum atoms in a covalent bond. The crystal structure is hexagonal lattice structure, and the sapphire crystal belongs to the middle crystal in the symmetric classification of crystal. Family, trigonal system.
In terms of color, pure alumina crystals are transparent and colorless, and sapphire appears in different colors because ions of different color elements penetrate and grow sapphire. When sapphire crystals contain titanium ions (Ti3+) and iron ions (Fe3+) in nature, the crystals appear as blue sapphire (Blue Sapphire).

Crystal performance
Chemical formula	Al2O3
Crystal structure	Hexagonal system
Lattice constant	a=b=0.4758nm，c=1.2991nm α=β=90°，γ=120°
Space group	R3c
Number of molecules in unit cell	2
Optical performance
Transmission band（μm）	0.14-6（Which is in the range of 0.3-5 T≈80%）
dn/dt（/K @633nm)	13x10-6
Refractive index	n0=1.768 ne=1.760
Absorption coefficient α	3μm—0.0006 4μm—0.055 5μm—0.92
Refractive index n	3μm—1.713 4μm—1.677 5μm—1.627
Mechanical and thermal properties
Density（g/cm3）	3.95—4.1
Moh's hardness	9（Second only to diamonds：10）
Young's modulus（GPa-1）	380
Breaking strength（MPa-1）	400
Bending strength	895MPa
Compressive strength	2GPa
Melting point（℃）	2040—2050
Boiling point（℃）	3000
Thermal conductivity（W·m-1·K-1）	24
Thermal expansion coefficient(K-1)	8.8×10-6
Specific heat(J/g)	0.782
Heat capacity(J/mol·K)	77
Poisson's ratio	0.27—0.29
Resistivity（Ω·cm）	1014
Dielectric constant（F·m-1）	11.5（∥c），9.3（⊥c）
Comparison of thermal conductivity in glass materials
Whiteboard	1.00W/m·K
Quartz	1.40W/m·K
Crystal	8.00W/m·K
Sapphire	42.0W/m·K

Characteristics and applications of sapphire
1、Sapphire has the best overall performance and is the most widely used oxide substrate material.（substrate materials），Mainly used as a semiconductor thin film substrate material, a large-scale integrated circuit substrate, and the like.
2、Sapphire crystals are also excellent window materials for high-end military equipment, missiles, submarines, satellite space technology, detection and high-power lasers, high-quality optical materials, wear-resistant bearing materials, etc.，Especially in the missile fairing, submarine window and atomic clock and other military products have an irreplaceable role.
3、Optical components, watch crystals, optical windows, detection windows and their applications
Sapphire single crystals can be fabricated into experimental optical components such as lenses, prisms and mirrors due to their ideal optical and mechanical properties, as well as scientific instruments such as gravity wave detectors.
Sapphire single crystal has wide transmission band, high transmission, high strength, high temperature resistance, wear resistance, corrosion resistance, low scattering, high hardness, high strength, low modulus of elasticity, high melting point, high thermal conductivity, high resistance Thermal shock quality factor, low heat radiation, jet fuel resistance, hail, rain, sea water, salt spray and sand scouring and corrosion, resistant to strong light irradiation and can be used as equipment for working in harsh environments such as high temperature and high pressure. Observation window and detection window, such as: high temperature resistant thermocouple and boiler water level gauge, wear resistant commodity barcode scanner window.
It is an excellent alternative to current multi-spectral sulfur-based window materials.
4、Sapphire fiber sensor and its application
Sapphire single crystal fiber sensor has good optical transmission characteristics in the visible to near-infrared region and high temperature resistance of sapphire single crystal, making sapphire fiber suitable for near-infrared laser transmission in high temperature sensing and biomedical fields.
In addition to the advantages of high dynamic range, high sensitivity, fast response, and anti-electromagnetic interference, the sapphire single crystal fiber temperature sensor can realize a wide range (room temperature - 2000 ° C) and high precision (0.2%, 1000 ° C). Time), high signal-to-noise ratio (1×106dB, 1000°C), large bandwidth (10kHz) temperature measurement, and widely used in plasma deposition, high-frequency electric heating furnace and high-temperature hot air flow.
In addition to measuring temperature and near-infrared laser transmission, the sapphire fiber sensor can continuously monitor the operation of systems in high temperature, acidic and alkaline environments up to 1600 °C, such as structural properties, material degradation, and measurement such as pressure and stress. Physical and chemical parameters such as strain and chemical concentration.
5、Doped sapphire single crystal thermal (light) light-emitting material and application thereof
α- Al2O3 :C crystals used in the manufacture of thermoluminescence detectors have the following characteristics:
（1）The thermoluminescence sensitivity is high, which is 40-60 times of the commonly used thermoluminescence crystal LiF: (Mg, Ti); the luminescence peak shape near 187 ° C is single, and the effective atomic number is relatively low (10.2);
（2）Low background dose response threshold (10-6Gy), radiation dose response is linear-sublinear, linear response range is wide (10-6-10Gy);
（3）α- Al2O3 :C The emission peak at 420 nm of the crystal is just at the optimum peak of the photomultiplier tube response. Under low dose conditions, the α-Al2O3:C crystal detector can be reused without annealing.