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NaZr 2-x B x (PO 4) 3-2x (SO 4) 2x (0 ≤ x ≤ 1.25, B = Mg, Co, Ni, Cu, Zn), and NaZr 2x R x (PO 4) 3-x (SO 4) x (0 ≤ x ≤ 1.25, R = Al, Fe) phosphate-sulfates series have been prepared by a sol-gel process. These compounds belong to the NaZr 2 (PO 4) 3 (NZP) structure family and crystallize in hexagonal crystal system, space group R3 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 NaZr 1.25 Cu 0.75 (PO 4) 1.5 (SO 4) 1.5 was studied in the range 25-700°C. Thermal expansion coefficients and thermal expansion anisotropy were found to be α a =

Na x Sr 1 -2x Nd x MoO 4 (x = 0-0.5, Δx = 0.1) solid solutions with the scheelite structure have been synthesized for the first time and their crystallographic parameters have been determined as functions of composition and temperature. Their thermal expansion coefficients have been determined in the temperature range 25-1000°C: α a = (12.9-14.9) × 10 -6 °C -1 and α c = (24.9-25.9) × 10 -6 °C -1 . Using spark plasma sintering at t max ≈ 872-985°C and τ ≈ 650-750 s, we have prepared ceramics with relative densities in the range 97-99%.

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