THERMAL-EXPANSION OF POROUS (CA1-X,MGX)ZR4(PO4)6 CERAMICS

The porous (Ca1-x, Mgx)Zr4(PO4)6-CMZP ceramics, which belong to the ultra-low thermal expansion [NZP] family, exhibit a near-zero coefficient of thermal expansion. Experimental results showed that the bulk thermal expansion of the polycrystalline CMZP ceramics is unchanged with varying porosity, but changes significantly with the composition and grain size of the ceramics. The coefficient of thermal expansion (CTE) of the porous CMZP ceramics varies from positive to negative with an increase of grain size and can be qualitatively explained by a model using hexagonal model grains. Thermal expansion hysteresis was found to alter with the grain size of the CMZP ceramics and it is worthwhile to note that the thermal history appears to affect the hysteresis phenomenon as well as CTE.