Synthesis And Characterization Of SrTiO₃-based Powders

SrTiO₃ as a typical perovskite oxide is widely used in electronic and mechanical applications due to its low dielectric loss and good thermal stability. And it can be made into high and middle voltage ceramice capacitors, boundary layer ceramic capacitors and low voltage dependent resistors. Because of its wide band gap (3.2eV) and high photo-catalytic activity, SrTiO₃ can also be used in producing hydrogen, degrading polluted organic and photochemical cells. With the development of electronic industry, performance of electronic ceramic material was required higher. People devote more attraction on synthesizing electronic ceramic material. The methods of preparing SrTiO₃ powders include solid-state method, co-precipitate method, sol-gel method, hydrothermal method, etc.In this paper we used Composite-hydroxide-mediated approach and solvothermal method to synthesize SrTiO₃ and Sr_1-xMn_xTiO₃ powders. The phase distribution of the composites and microscopic structure characteristic were investigated by means of X-Ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and optical properties of the samples were tested by ultraviolet-visible spectra (UV-vis) and photoluminescence spectra (PL).SrTiO₃ particles were synthesized by composite-hydroxide-mediated approach. The growth mechanism of SrTiO₃ nanorods was discussed and it was found that the formation of SrTiO₃ nanorods involved four steps: dissolution→homogeneous nucleation→growth of regular sheets→coordinative self-assembles. SrTiO₃ powders were also synthesized by solvothermal method. Experimental results indicated that the particles grow larger along with increasing the reation temperature.As-synthesized Sr_1-xMn_xTiO₃(x=0.02, 0.05, 0.1) powders by CHM have lengths from 2μm to 10μm and widths about 0.5μm-1μm. The phase and optical property would change with different Sr/Mn molar ratio. Solvothermal method also was employed to prepare Sr_1-xMn_xTiO₃(x=0.02, 0.05, 0.1, 0.2). No phase segregation was observed even after doping 20mol% Mn²⁺ to SrTiO₃, indicating that Mn²⁺ ions successfully substituted Sr²⁺ ions without changing the structure of SrTiO₃. Red shift of absorption edge of SrTiO₃ powders was observed and band gap of the products decreased with increasing doping concentration of Mn. Two violet-blue luminescence emission bands located at 405nm and 474nm under ultraviolet excitation (254nm) were observed and were ascribed to oxygen vacancies which were some intrinsic defect centers of SrTiO₃.