The Characterizations Of M₃TeO₆?M=Cu,Co?and Their Physical Properties Under High Pressure

Tellurium-based compounds are promising dielectric candidates for multilayer ceramic capacitors and low temperature co-fired ceramics due to their low sintering temperature and good dielectric properties.At present,the research on its structure and performance has aroused great enthusiasm of most researchers.High pressure technology provides a new method for discovering many new substances,new structures and new properties different from those under normal pressure and opens a bright new window to the materials research.In this thesis,M₃TeO₆?M=Cu,Co?was synthesized by solid-phase sintering method.It was characterized conventionally and then the effects of high pressure on the structural properties of these material were investigated.The obtained results are as follows:?1?Cu₃TeO₆ with cubic phase was prepared by solid phase method.Scanning electron microscope?SEM?showed that the particles of Cu₃TeO₆ sample were closely packed,and it had high dense capacity.?2?The crystal structure stability of Cu₃TeO₆ was studied by high-pressure Raman and high-pressure in-situ synchrotron radiation X-ray diffraction.The high-pressure Raman spectra indicated that new peaks appeared when the pressure reached 11.2 GPa.The high-pressure in-situ synchrotron radiation X-ray diffraction patterns showed that Cu₃TeO₆ underwent a structural phase transition from cubic phase Ia-3 to orthorhombic phase Ibca under high pressure?8.6 GPa?.?3?The monoclinic Co₃TeO₆ was prepared by solid phase method.SEM showed that the surface of Co₃TeO₆ sample was rough with obvious pits and attached by many tiny grains.?4?The high-pressure Raman spectra of Co₃TeO₆ were carried out.The results showed that new peaks appeared when the pressure reached 5.9 GPa.It indicated that the structural phase transition might occur in Co₃TeO₆ under high pressure.