Synthesis and thermal expansion behavior of liquid phase sintered CaZr 4(PO 4) 6–Li 2O

Abstract

Lithium oxide was introduced into the CaZr 4(PO 4) 6 lattice to densify the material to its theoretical density through liquid phase sintering. Although the liquid phase significantly enhanced the densification rate, due to the high solubility of the Li 2O liquid phase in the solid, a transient liquid phase was generated, which resulted in microstructures that were extremely sensitive to both composition and processing conditions. It was determined that 1 wt.% addition of Li 2CO 3 with accelerated sintering schedule produced the theoretical density of CaZr 4(PO 4) 6 and further addition of Li 2CO 3 rapidly decreased the sintered density. Minimum bulk thermal expansion of negative 5×10 −6 °C −1 was obtained with the addition of 5 wt.% Li 2CO 3. The thermal hysteresis effect was minimized at the composition of 2.5 wt.% Li 2CO 3. It was demonstrated that by changing the composition and sintering schedule, the theoretical density of CaZr 4(PO 4) 6 could be reached through liquid phase sintering and the thermal expansion characteristics can be engineered as desired by controlling its composition and sintering schedule.