Precipitation synthesis and sintering of lanthanum doped yttria transparent ceramics

Co-precipitation method was used to prepare lanthanum doped yttria nanopowder. After calcinations at 1000 °C, lanthanum ion entered into the yttria lattice. Effect of lanthanum oxide as an equal valent additive on the sintering of yttria was investigated. The addition of lanthanum ions was found to be effective for promoting the densification process during sintering, and make it easier for the ceramic to be transparency at moderate 1700 °C in vacuum. After sintering at 1500 and 1700 °C for 4 h in vacuum, translucent and transparent poly-crystalline ceramics with uniform lanthanum distribution was obtained, respectively. The grain size (75 ± 13 μm) of 7% lanthanum doped yttria sintered at 1700 °C was about 10 times bigger than that sintered at 1500 °C (7.6 ± 1.9 μm). The refractive indices of lanthanum ion doped sample were higher than undoped sample in vis-UV light range. The in-line transmittance of 2 mm thick samples sintered at 1700 °C reached 74% at 800 nm (89.7% of theoretical transmittance) wavelength.