Crystal phase control and ionic conductivity of magnesium ion-doped lanthanum oxyfluoride

Abstract

Novel F⁻ ion conducting solid electrolytes of La_1−xMg_xO_1−δF were developed by doping Mg²⁺ cation into the La³⁺ site of lanthanum oxyfluoride (LaOF) solid. By doping the smaller size and lower valent Mg²⁺ cation into the La³⁺ site, both the suppression of the phase transition from α- to β-form and the improvement of conductivity were simultaneously realized. Among the samples holding the single phase of α-LaOF type structure, the La_0.8Mg_0.2O_1−δF solid showed the highest F⁻ ion conductivity, which was ca. 46 times higher than that of non-doped LaOF solid.