Sintering behavior of niobium- and calcium-doped TiO2 ceramics

[[abstract]]The sintering behavior of niobium- and calcium-doped TiO2 ceramics was greatly affected by dopants, the uniformity of the green compact and the crystallite size of the powders. Compacts with rutile powders had bad sinterability and the highest sintered density achieved was only 94.5% of the theoretical density. In contrast, compacts with anatase powders had good sinterability and most of them achieved 97% of the theoretical density even when sintered at 1050°C for 2 h only. The sintering kinetics at low temperature for compacts with rutile powders were determined by the competition between the oxygen vacancy and the second phase. The crystallite size and the uniformity of the green compact were the controlling factors for the sintering kinetics for anatase powders sintered above 1150°C. The second phases were identified as CaTiO3 and CaTiSiO5 by X-ray diffraction (XRD) and the liquid phases were proposed as phases containing calcium, titanium, silicon and oxygen or calcium, niobium, titanium and oxygen for samples sintered at 1350°C for 8 h[[fileno]]2020301010027[[department]]材料科學工程學