CaNb2O6 ceramics prepared by a reaction-sintering process

CaNb2O6 columbite ceramics produced by a reaction-sintering process were investigated. CaCO3 was mixed with Nb2O5 then pressed and sintered into CaNb2O6 ceramics without any calcination stage involved. Pure columbite CaNb2O6 phase was obtained successfully. After 1420 °C sintering for 2 h, a density 4.37 g/cm3 (92% of the theoretical value) were obtained. Some sub-micron CaO particles were segregated at the surfaces of CN grains at 1350-1450 °C. Round grains formed at 1330-1400 °C and long shaped grains are found in CN pellets sintered at temperatures above 1400 °C. 3.9-8.1 μm grain sizes are formed in CN pellets sintered at 1330-1400 °C for 2 and 4 h.