Crystal chemistry and thermal expansion of Cd0.5Zr2(PO4)(3) and Cd0.25Sr0.25Zr2(PO4)(3) ceramics

Cd0.5Zr2(PO4)(3) (CdZP) and the partially substituted phase Cd0.25Sr0.25Zr2(PO4)(3), prepared by the sol-gel route, belong to the NZP family. The structure of CdZP (S.G.R (3) over bar) has been established by the Rietveld method. The thermal behavior of CdZP, investigated by X-ray powder diffraction, is anisotropic, i.e., the structure expands along c axis and contracts along a axis. Dilatometric measurements and SEM micrographs of ceramics, sintered with 5% ZnO, show that CdSrZP presents the advantage to decrease microcracking, and then anisotropy,occurring during the heating cycle. The thermal expansion coefficient a(bulk) of the ceramic CdSrZP is very small (0.6 x 10(-6)degrees C-1).