Ionic conductivity of congruently melting Ca0.6Sr0.4F2 and Ca1 − x − y Sr y R x F2 + x (R = La, Ce, Pr, Nd) single crystals with fluorite structure

Single crystals of congruently melting compositions of the Ca0.6Sr0.4F2 and Ca1 − x − y Sr y R x F2 + x (R = La, Ce, Pr, Nd; x = 0.16–0.21; y = 0.07–0.16) solid solutions with fluorite structure have been grown by the Bridgman-Stockbarger method. Their electrical properties have been investigated in the range from 473 to 823 K, and it is shown that they are ionic conductors. For Ca0.6Sr0.4F2 crystals, the ionic conductivity σ = 2 × 10−6 S/cm at 673 K, and the ion transport activation energy E a = 1.1 eV. For Ca0.77Sr0.07La0.16F2.16, Ca0.70Sr0.11Ce0.19F2.19, Ca0.65Sr0.15Pr0.20F2.20, and Ca0.58Sr0.21Nd0.21F2.21 crystals, the values of σ lie in the range from 9 × 10−7 to 2 × 10−6 S/cm at 500 K, and the activation energy E a is 0.88–0.93 eV. The concentration and mobility of ionic charge carriers in Ca1 − x − y Sr y R x F2 + x crystals have been calculated.