Synthesis And Physical Properties Of Perovskite Oxide Containing Pb Or Te

The perovskite-type oxides become a research focus in the field of materials because of excellent physical and chemical properties,such as ferroelectricity,ferromagnetism,piezoelectricity,etc..In addition,the Pb-containing or Te-containing perovskite compounds has been widely studied due to the structural distortion and the emergence of new properties.Therefore,synthesis and physical properties of perovskite oxide containing Pb2+ cation and Te2+ cation have been studied in this paper.Three mainly work have been reported in this paper.First one,the tetragonal,orthorhombic and cubic PbTeO3 were synthesized by melting method,the phase analysis of the synthesized samples was carried out by powder X-ray diffraction.And none of samples was single phase.Second one,the tetragonal PbTeO3 single crystal samples have been prepared by hydrothermal method,and the results of X-ray diffraction,infrared absorption spectrum,Raman spectrum and high pressure Raman spectrum of tetragonal PbTeO3 are following:(1)The four absorption peaks observed in the infrared absorption spectroscopy were located at 634 cm-1,649 cm-1,670 cm-1 and 734 cm-1,respectively.All of the absorption peaks are belong to the stretching vibration of the Te-0 bond.(2)Compared with the results of the theoretical calculations,it is found that the Raman peaks located in the 600 cm-1 to 800 cm-1 in the Raman spectra are attributed to the symmetric and anti-symmetric stretching vibration modes of Te-0 bonds in TeO32-.The Raman peaks located in the 178 cm-1 to 400 cm-1 are attributed to the rotation,bending,swing,the external vibration modes of TeO32-.The Raman peaks below 144 cm-1 consist of lattice modes and external modes of TeO32-polyhedral unit.(3)In situ high-pressure Raman spectroscopy,the Raman spectra split into two Raman peaks at the 119 cm-1 position when the pressure increased to 13.4 GPa,this may due to the rotation of the TeO32-polyhedron rather than the phase transition of PbTeO3.When the pressure rose to 18 GPa,the Raman peaks appear to be broadened and the weakened,indicating that the Raman vibration modes begin to soften,and crystal structure of tetragonal PbTeO3 appearing unstable situation.Last one,the single crystals of orthorhombic Pb2Te3O8 was synthesized by hydrothermal method.The infrared absorption spectra,UV-Vis absorption spectra.Raman spectroscopy and high pressure Raman spectrum of Pb2Te3O8 were analyzed:(1)The infrared absorption peak positions of Pb2Te3O8 are located at 404 cm-1,578 cm-1,658 cm-1,694 cm-1 and 739 cm-1.(2)According to the UV absorption spectrum of Pb2Te3O8,Pb2Te3O8 is an insulator with a band gap width of 3.57 eV.(3)The Raman spectra of Pb2Te3O8 single crystal were investigated.According to the related studies,we infer that the six Raman peaks locate at 637 cm-1,657 cm-1,689 cm-1,723 cm-1,736 cm-1 and 761 cm-1 are belong to the internal vibration mode.The vibration modes in the 50 cm-1 to 400 cm-1 frequency correspond to the lattice vibration modes and the external vibration modes of Te30O84-.(4)In situ high-pressure Raman spectroscopy shows that the orthorhombic Pb2Te3O8 can be stable until the pressure reaches 21.8 GPa without phase transition.