Preparation and Thermal Expansion of Calcium Iron Zirconium Phosphates with the NaZr2(PO4)3 Structure

Abstract

Ca_{0.5(1 + x)}Zr_2–xFe_x(PO₄)₃ phosphates have been synthesized by a sol–gel process. The individual compounds and solid solutions obtained crystallize in the NaZr₂(PO₄)₃ structure (trigonal symmetry, sp. gr. R\(\bar 3\)). Using high-temperature X-ray diffraction, we have determined their thermal expansion parameters in the temperature range from 25 to 800°C. With increasing x, the magnitudes of their linear thermal expansion coefficients and thermal expansion anisotropy decrease. Most of the synthesized phosphates can be rated as low-thermal-expansion compounds and can be regarded as materials capable of withstanding thermal “stress.”