The Investigation Of Transport And Thermoelectrical Properties Of Rare Earth Sm Doped SrTiO₃ System

Thermoelectric materials and thermoelectric effects are responsible for the direct conversion of heat into electrical energy and vice versa. Metal oxides are more suitable for high temperature applications. Their structural and chemical stabilities,oxidation resistance, low-cost and without pollutions, have attracted much attention recently.This paper first tries to use the Sol-gel method, high temperature and high pressure method, solid state reaction method to synthesize Sm_xSr_1-xTiO₃, although the sample was partial single-phase sample, further test has shown that the quality of the sample needs to be improved. Sm_xSr_1-1.5xTiO₃ (x = 0, 0.02, 0.04, 0.06, 0.08) were prepared at 1470℃in the forming gas (5%H2/Ar) for 6 hours, the solution limitation is about 8mol%.Sample density tests showed that samples have a very high density. XRD analysis did not reveal the presence of impurities. with the increase of doping, diffraction peaks have a slight mobile to the high angle. Redox titration shows oxygen content as increase of doping gradually reduced.The sample resistivity study finds after rare earth doped significantly reduce resistivity of simple. The analysis of conductive mechanism finds that in low temperature region mechanism was in line with heat activated hopping conduction models, and high temperature zone was in line with a small polaron hopping conduction model.A detailed study of thermal conductivity and thermoelectric power has been done. The study showed that the main impaction of the thermal conductivity was the scattering of point defects, the analysis of thermopower showed that thermoelectric power at room temperature approximately meet non-degenerate semiconductor model. Then we calculated Fermi level, rare earth doping improved Fermi level, changed the shape and the energy band structure, and therefore changed the Seebeck coefficient under the above analysis showed that rare earth doping effectively reduced thermal conductivity and resistivity, thermoelectric power, Sm_xSr_1-1.5xTiO₃ system of thermoelectric properties further enhanced.