New Phosphate-Sulfates with NZP Structure

NaZr2-x B (x) (PO4)(3-2x) (SO4)(2x) (0 x 1.25, B = Mg, Co, Ni, Cu, Zn), and NaZr2-x R (x) (PO4)(3-x) (SO4) (x) (0 x 1.25, R = Al, Fe) phosphate-sulfates series have been prepared by a sol-gel process. These compounds belong to the NaZr2(PO4)(3) (NZP) structure family and crystallize in hexagonal crystal system, space group R c. Limited solid solution series were found to exist; their formation temperatures and thermal stability limits were determined. Particle sizes as determined by microstructure observation were 50-200 nm, and for Cu- and Zn-containing samples, 200-500 nm. The thermal expansion of phosphate-sulfate NaZr1.25Cu0.75(PO4)(1.5)(SO4)(1.5) was studied in the range 25-700A degrees C. Thermal expansion coefficients and thermal expansion anisotropy were found to be alpha(a) =-5.40 x 10(-6) A degrees C-1, alpha(N) = 18.88 x 10(-6) A degrees C-1, alpha(avg) = 2.69 x 10(-6) A degrees C-1, and Delta alpha = 24.28 x 10(-6) A degrees C-1.