Refractive index and elastic properties of single-crystal corundum (α-Al2O3) up to 2100 K

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Abstract
We show that Brillouin scattering can be used to measure the elastic and optical properties of materials to very high temperatures. We have measured the elastic constants C 11, C 33, and C 44 of single‐crystal sapphire in the temperature range 300–2100 K extending by 300 K the highest temperature previously attained with ultrasonic resonance techniques. The temperature dependence of the ordinary and extraordinary refractive indicesn o and n e in the same temperature range have been obtained for the first time. Although both n o and n e are temperature dependent, the ratio n o /n e is found to be almost temperature independent.