Studies And Modification Of Transmittance Property Of Y₂O₃ Doped ZrO₂ Ceramics

ZrO₂ transparent ceramics have wide applications in electronic fields and at high-temperature and high pressure due to their good transparency, corrosion resistance as well as heat resistance. They can be used as lighting and special optical devices, etc. First, sinterability and transmittance of Y₂O₃ doped ZrO₂ were investigated. Then CaF₂ and ZnO were added to 8Y-ZrO₂ to improve its sinterability and transparency due to the poor sinterability of 8Y-ZrO₂ that lead to very low transparency.The materials with formula Zr1-xYxO2-0.5x (x=0.06, 0.10, 0.16, 0.24) were prepared by solid-state reaction at different temperatures for different times. Bulk density and relative density of samples were measured according to the Archimedes principle. The results showed that the relative density of the samples with x=0.06 (3Y) sintered at 1400℃for 3h and 1450℃for 3h, respectively, were the highest, reaching 99.1% and 99.3%; the relative density of the sample with x=0.10 (5Y) sintered at 1450℃for 3h was 98.8%. The relative density of the samples with x=0.16 and 0.20 (8Y and 12Y) sintered at 1600℃for 4h were only 95.7% and 92.4%. The order of the visible and IR-transmission were 3Y> 5Y> 8Y. The IR-transmission of 3Y and 5Y samples reached as high as 70%.8Y-ZrO₂ powder was also prepared by alcohol-aqueous co-precipitation method and microwave drying to improve its sinterability. Powder with higher specific surface area was obtained compared with the conventional co-precipitation and oven drying. The specific surface area reached 8.93 m2·g-1, equivalent grain size was 17.09 nm. Unfortunately, the relative density only reached to 95.7% after sintering at 1600℃for 4h. The transmittance of the sample has not much improved because its density is not high enough.CaF₂ inclusion can reduce the sintering temperature of 8Y-ZrO₂ ceramics through liquid phase sintering and forming solid solution. When the CaF₂ content was 2mol% and the sintering condition was 1450℃/4h, the relative density was as high as 99.2%, but SEM showed that some CaF₂ existed along the grain boundary which greatly degraded the transmittance. The order of transmittance was C1> C4> C3> C2.ZnO is an effective sintering additive for 8Y-ZrO₂ through forming solid solution. When ZnO content was 1.5mol% and the sintering condition was 1380℃/4h, the relative density reach up to 99.6%. The shape of grains was irregular and the grain size was about 5μm. At the same time, the grain boundary was clean, so the transmittance was much more increased. The highest transmittance was obtained corresponding to the wavelength of 6.7μm. The transmittance of the samples with ZnO addition reached 40%, much higher than that without ZnO.