Ionic conductivity of lanthanoid silicates, Ln10(SiO4)6O3(Ln = La, Nd, Sm, Gd, Dy, Y, Ho, Er and Yb)

Abstract

Ionic conductivities have been investigated for lanthanoid silicates of the Ln₁₀(SiO₄)₆O₃ solid solution series and related compounds. The activation energy and conductivity at 500 °C were estimated to be 69 kJ mol^–1 and 1.8 × 10^–4 S cm^–1 for La₁₀(SiO₄)₆O₃ and 71 kJ mol^–1 and 1.5 × 10^–4 S cm^–1 for Nd₁₀(SiO₄)₆O₃. The a and c lattice constants of the hexagonal phase decreased with decreasing radius of the Ln³⁺ ion for Ln₁₀(SiO₄)₆O₃(Ln = La, Nd, Sm, Gd and Dy). The activation energy increased and the conductivity decreased when Ln³⁺ ions with smaller ionic radii were used. The sole carrier in these materials is the O^2– ion.