Effect of Impurities on the Strength of CaF₂ Single Crystals

Abstract

<p>Pure and doped CaF₂ single crystals were grown from melts by Czochralski technique. The doped crystals contained two levels of Na⁺, K⁺, V³⁺ and Y³⁺ impurities. The crystals were subsequently annealed and analysed for impurities. Samples were mechanically tested in compression at 450 and 600°C, and the 0.1% proof stress noted. An attempt was made to explain the observed hardening by Fleischer's theory of solid solution hardening in the case of V³⁺ and Y³⁺ -doped CaF₂ and by precipitation hardening theory in the case of Na⁺ and K⁺ -doped crystals.</p>