Thermal expansion of Ca1−xSrxZr4(PO4)6 ceramics

Different compounds of the low thermal expansion solid solution series of Ca1−xSrxZr4(PO4)6 were synthesised by solid-state reaction. Room temperature crystallographic investigations of CaZr4(PO4)6 powder samples revealed, that with substitution of Ca by Sr the lattice parameter considerably increased in c-direction while the change in a-direction was marginally negative. High-temperature X-ray powder diffraction up to 1000 °C pointed out an anisotropic thermal expansion behaviour of these compounds which, however, decreased progressively with increasing Sr content. Sintered samples were prepared from these compounds in which 3 and 5 wt.% ZnO were added to promote sintering. The dilatometric thermal expansion values of the bulk samples are discussed in the light of the corresponding crystallographic data of the powder samples. The results were compared with data published in the literature.