NEW SOLID-SOLUTIONS LI(MIV)2-X(NIV)X(PO4)3 - (L=LI,NA) (M,N-GE,SN,TI,ZR,HF) - SYNTHESIS, X-RAY-DIFFRACTION ANALYSIS AND IONIC-CONDUCTIVITY

Definite Nasicon-like compounds LI(MIV)2(PO4)2 and new solid solutions LI(MIV)2-x(NIV)x( PO4)3 (L = Li,Na, M,N = Ge,Sn,Ti,Zr,Hf) have been synthesized and studied by X-ray powder diffraction and ionic conductivity measurements. A new single phase of the compound LiSn2(PO4)3 has been obtained for the first time. Concerning the solid solutions, continuous series of well-crystallized single phases can be synthesized in the Ti ↔ Ge, Sn ↔ Ti, and Sn ↔ Zr systems, but not in the Ge ↔ Zr, Zr ↔ Ti, and Sn ↔ Ge systems, because of important differences of ionic radii. When solid solutions are possible, the variation of ionic conductivity with x is regular except in LiSn2-xZrx(PO4)3, where it reaches a maximum near x = 1 (σ ≈ 7 10-3 Ω-1 cm-1 at 600 K). © 1991.