Preparation of NZP-Type Ca0.75 + 0.5xZr1.5Fe0.5(PO4)3 –x(SiO4)x Powders and Ceramic, Thermal Expansion Behavior

Abstract

Ca_{0.75 + 0.5x}Zr_1.5Fe_0.5(PO₄)_{3 –x}(SiO₄)_x (x = 0–0.5) solid solutions have been synthesized by a sol–gel process and characterized by X-ray diffraction, IR spectroscopy, and differential scanning calorimetry. As expected, the synthesized phosphatosilicates crystallize in a NaZr₂(PO₄)₃-type structure (trigonal symmetry, sp. gr. R\(\bar {3}\)c). The thermal expansion of the solid solutions has been studied by high-temperature X-ray diffraction in the temperature range from 25 to 800°C. Their thermal expansion parameters have been calculated and analyzed as functions of composition. High-density ceramics based on the Ca_0.875Zr_1.5Fe_0.5(PO₄)_2.75(SiO₄)_0.25 phosphatosilicate have been produced by spark plasma sintering and their structure and properties have been studied in detail.