IONIC-CONDUCTIVITY OF LANTHANOID SILICATES, LN(10)(SIO4)(6)O-3 (LN=LA, ND, SM, GD, DY, Y, HO, ER AND YB)

Ionic conductivities have been investigated for lanthanoid silicates of the Ln(10)(SiO4)(6)O-3 solid solution series and related compounds. The activation energy and conductivity at 500 degrees C were estimated to be 69 kJ mol(-1) and 1.8 x 10(-4) S cm(-1) for La-10(SiO4)(6)O-3 and 71 kJ mol(-1) and 1.5 x 10(-4) S cm(-1) for Nd-10(SiO4)(6)O-3. The a and c lattice constants of the hexagonal phase decreased with decreasing radius of the Ln(3+) ion for Ln(10)(SiO4)(6)O-3 (Ln = La, Nd, Sm, Gd and Dy). The activation energy increased and the conductivity decreased when Ln(3+) ions with smaller ionic radii were used. The sole carrier in these materials is the O2- ion.