A Challenge to Prepare Perovskite Structure SnTiO3
|Course||Condensed Matter Physics|
|Keywords||SnTiO3 Perovskite Piezoelectric material HPHT sol-gel|
Most materials with large electric polarization are based on the perovskitestructure ABO3, such as PbTiO3. SnTiO3with perovskite structure has been predictedas potential environmentally benign ferroelectric material calculated by first principleswithin density functional theory （DFT） in recent years. The ferroelectricity with apolarization in SnTiO3is at least as high as in PbTiO3. Full geometry optimizationprovides a stable tetragonal structure relative to cubic one reported by Matar. A largertetragonality leading to a higher polarization and a larger dielectric constant wereidentified. With respect to PZT, it has superior physical properties of the dielectric,ferroelectric, pyroelectric. Up to date, SnTiO3has been focused on the piezoelectricmaterials as a new environmentally piezoelectric ceramic.Till to now, it is defeated to synthesize SnTiO3using solid state reactions fromSnO and TiO2. This is due to the disproportionation reaction of tin（II） oxide SnO totin（IV） oxide （SnO2） and tin metal （Sn）. Complex oxides containing Sn2+have beenreported only for several compounds, for example SnWO4, SnNb2O6and Sn2TiO4. So,SnTiO3may be expected as a metastable phase with positive cohesive energies. It iswell known that the different raw materials can affect the reaction route and chemicalreaction barrier and even the ability to react. In this work, the synthesis explore of theSnTiO3was carried out by high pressure and high temperature（HPHT）, sol-gel andconventional solid-state reaction with the tin source Sn, SnO, SnO2, SnCl2andtitanium source H2TiO3, TiO2as the raw materials.The samples has been synthesized via TiO2/H2TiO3, SnCl22H2O, Sn after3hours sintered under the condition of the pressure of4.8GPa and1073K andcharacterized by XRD powder diffraction. The diffraction peaks of the phase weredifficultly matched to PDF card. And the peak position of a new phase were found at21.62°,29.01°,33.4°,34.8°,37.8°,49.09°,50.96°,59.8°. The new phase containingSn2+is weak acid and strong water absorption. This result may be useful to prepare SnTiO3. Tin monoxide, SnO, is metastable at ambient conditions and it decomposesby a disproportionation reaction with a noticeable rate to Sn and SnO2above600℃atHPHT. This result is consistent with the reported literature. So it is inappropriate tosynthesize SnTiO3directly from SnO at HPHT.Monoclinic BiSbO4is found to be an effective visible light responsivephotocatalyst in the degradation of the organic dye. BiSbO4has been successfullyprepared by sol-gel method from Sb2O3and Bi（NO3）35H2O. The pure phase has beensuccessfully obtained above900℃. The grain size,800nm, was observed from thescanning electron microscopy （SEM）. The oxidizing reaction from Bi3+inBi（NO3）35H2O to Bi5+has been effectively restrained. This result may be helpful toprepare SnTiO3from Sn2+by sol-gel method.The Crystal structure of the ternary oxide Sn2TiO4containing Sn2+, which isisostructural to Pb3O4, is built up by one-dimensional chains of edge-sharing metalcentered octahedra TiO6along the c-axis and the chains are connected by Sn2+havingstereo active lone pair. In our work, we attempted to prepare Sn2TiO4by anion-exchanging reaction between potassium titanates synthesized via K2CO3and TO2as starting materials and SnCl2. The results confirmed that Sn2TiO4cannot besynthesized under the condition of low vacuum and the H2O existed.