Fabrication of fine-grained and high thermal properties Y2O3 transparent ceramics without sintering aids

Infrared transparent pure Y2O3 nanoceramics were fabricated from citric acid sol-gel combustion synthesized nanopowder and through the combination of hot pressing and hot isostatic pressing. The influence of calcination temperature on the morphology, particle size and agglomeration state of the nanopowders during powder synthesis process was investigated. Powder with a particle size of 15.5 nm and agglomeration factor of 3.3 was obtained with the calcination temperature at 700 degrees C for 4 h. Green compact with homogenous microstructure and improved sintering activity was consolidated by cold isostatic pressing after dry pressing. Y2O3 transparent ceramic was achieved with hot pre-sintering at 1400 degrees C without holding plus hot isostatic pressing at 1450 degrees C for 2 h under 200 MPa pressure. As a result, the ceramic prepared with 1.0 mm thickness got the transmission of 80.4 %-83.9 % at 2.5 mu m-6.0 mu m wavelength with an average grain size of 413 nm. The sample's thermal conductivity was 12.84 W m-1 K-1 and the phonon energy was 592 cm-1, making it a promising material for IR transparent windows and host material for efficient infrared solid-state laser. The sintering mechanism was proposed and discussed.