The Fiber-Optic Thermometer Using Fluorescence Lifetime of the Spinel Crystal

Abstract

The chromium doped spinel crystals, MgAl₂O₄: Cr³⁺, have advantageous features for the fiber-optic thermometer. Since the spinel crystal has wide solid-solution region, the chemical composition of the spinel crystal varies with the composition of raw material. In order to clarify the influence of chemical composition on the characteristics of fiber-optic thermometer, spinel crystal with various compositions, x=MgO/(MgO+Al₂O₃)=0.40, 0.45, 0.50, 0.55, 0.60 were grown using a floating zone technique. The characteristics of the fiber-optic thermometer using spinel are found to vary greatly with chemical composition of spinel crystal. The stoichiometric specimen with x=0.50 shows the longest lifetime and large temperature coefficient. The stoichiometric spinel crystal is considered to be the most suitable sensor head for the fiber-optic thermometer.