“…It has a Na + resistivity at 300 o C of ρ < 5 Ω•cm for x~2 [3]. Nomura et al have performed a systematic investigation on the framework structure, the phase transition and electrical conductivity of zirconium phosphates, M II Zr 4 (PO 4 ) 6 (M = Mg, Ca, Ba, Mn, Co, Ni, Zn, Cd and Pb) [4,5]. In addition, Imanaka et al have studied Al, rare earth (Sc, Eu, Gd, Er, Tm, Yb and Lu) and tetravalent (Ti, Hf and Ge) cation conduction in phosphates and tungstates [6][7][8].…”