The synthesis, sintering, and thermal properties of (Ca_1−x, Mg_x)Zr₄(PO₄)₆ (CMZP) ceramics

(Ca_1−x, Mg_x)Zr₄(PO₄)₆ (CMZP) ceramics have been made by sol-gel and solid state reaction methods. Single phase (Ca_1−x, Mg_x)Zr₄(PO₄)₆ (x = 0.4) has been obtained. The densification of CMZP depends on the powder synthesis method. Near theoretical density can be achieved by cold pressing and sintering with the addition of a sintering aid. Bulk thermal expansion of CMZP is shown to depend on the phase composition, grain size, and presence of microcracks. By choosing different sintering temperatures and times, the thermal expansion of CMZP can be controlled. CMZP (x = 0.4) ceramics exhibit near zero bulk thermal expansion, low thermal expansion anisotropy, low thermal conductivity, and thermal stability up to 1500 °C.