Domain structures in LiTaO₃ particles dispersed in Al₂O₃ matrix ceramic composite

The domain structures in LiTaO₃ particles dispersed in the Al₂O₃ matrix ceramic composite were investigated systematically using the TEM technique. The results show that 90°C domain structures mainly occur in LiTaO₃ grains in LiTaO₃/Al₂O₃ (denoted by LTA) ceramic composite, which is impossible in the LiTaO₃ single crystal. This is a new discovery for hexagonal LiTaO₃. Domain structures in LiTaO₃ grains very greatly in LTA ceramic composites fabricated by different sintering methods. The influencing factors of domain structures are also discussed. Domain structures in LiTaO₃ grains in LTA fabricated by hot-pressing at 1500°C are mainly lamellar 90°C domains of high density and herring-bone 90°C domains. Besides lamellar and herring-bone 90°C domains, wedge shaped and band shaped 90°C domains are also found in LiTaO₃ grains in LTA prepared by cold isostatic pressing under a pressure of 200 MPa followed by pressureless sintering at 1300°C. Most band shaped 90°C domains and a few of wedge shaped 90°C domains are observed in LTA hot-pressed at 1300°C. The differences of domain structures in LiTaO₃ grains are related with the stress round LiTaO₃ grains acted by Al₂O₃ grains, the chemical composition of LiTaO₃ and the mechanical grinding and polishing in the process of fabricating specimens.