Synthesis and properties of La2(Mo1-xMx)2O9 (M = Nb, Ta) ionic conductors

La-2(Mo1-xMx)(2)O-9 (M = Nb, Ta; 0 < x less than or equal to 0.2) solid solutions were prepared, and their physicochemical and electrical properties were studied. Second harmonic generation measurements indicate that the solid solutions have a noncentrosymmetric structure and undergo a structural phase transition accompanied by a sharp increase in ionic conductivity, similar to that of La2Mo2O9. The transition temperature is found to decrease with increasing Nb or Ta content. The introduction of 5 wt % Nb increases the 800degreesC conductivity of the material.