A natural layered aluminosilicate pyrophyllite was used as the starting material for the preparation of fast ionic conductors of the form, Hf2-xNa1+3xAlxSi2xP3-2xO12. A single NASICON phase, with a C2/c space group, was found at x-values of less than 0.6. The volume of the unit cell, within this composition range, increased with increasing x-value. The composition with x = 0.6 exhibited an ionic conductivity of up to 0.0122S/cm at 350C, with a corresponding activation energy of 26.3kJ/mol.

W.Wang, X.Liu: Solid State Ionics, 1996, 89[1-2], 165-8