Processing of crack-free high density polycrystalline LiTaO3 ceramics

This work has successfully achieved high density (99.9%) polycrystalline LiTaO 3 . The keys to the high density without cracking were the use of LiF-assisted densification to maintain fine grain size as well as the presence of secondary lithium aluminate phases as grain growth inhibitors. The average grain size of the hot pressed polycrystalline LiTaO 3 is less than 5 μm, limiting residual stresses caused by the anisotropic thermal expansion. Dilatometry results clearly indicate liquid phase sintering via the added LiF sintering aid. Efficient liquid phase sintering allows densification during low temperature hot pressing. Electron microscopy confirmed the high-density microstructure. Rietveld analysis of neutron diffraction data revealed the presence of LiAlO 2 and LiAl 5 O 8 minority phases and negligible substitutional defect incorporation in LiTaO 3 .