Doping Effect On Thermoelectric Properties Of Perovskite Manganese Oxides

Because the thermoelectric material can be used in the electricity generation (Seeback Effect) and the refrigeration (Peltier Effect) aspect application, it arouses people's interest once more. The perovskite manganese is not cobalt base oxide compound, which represents a thermoelectric material important research direction.We first used the sol– gel method to prepare the manganese oxide compound thermoelectric material La_0.6Sr_0.4-xK_xMnO₃ , La_0.67Sr_0.33-xAg_xMnO₃andLa₁Sr_2-xAg_xMnO₇ powder , Then presses the powder the block under the 12 MPa intensity of pressure, obtains the sample which calcine in the high temperature again. Carried on the X-ray diffraction to the obtained sample (X ray) to analyze, we study the K ,Ag doping to the sample electronic resistivity, the Seebeck coefficient and figure of merit coefficient ZT and so on influence, Simultaneously ,we has discussed the sample electric conduction mechanism, used two item of models to explore the temperature to the sample Seebeck coefficient influence.Present paper's main research results are as follows:1. Used the sol– gel method to prepare the manganese oxide compound thermoelectric material La_0.6Sr_0.4-xK_xMnO₃,La_0.67Sr_0.33-xAg_xMnO₃ and La₁Sr_2-xAg_xMnO₇ powder. The sample electric conduction mechanism and the sample Seebeck coefficient conform to two models .2.We have studied thermoelectricity performance under the sample room temperature. Had the enhancement sample's figure of merit coefficient ZT through doping. And, the maximum figure of merit coefficient ZT of sample La_0.6Sr_0.2K_0.2MnO₃ may achieve 2.36×10^-5 in 160 K,. the maximum figure of merit coefficient ZT of sample La_0.67Sr_0.13Ag_0.2MnO₃ is 1.41×10^-4 in 151k, which is triple than the La_0.67Sr_0.33MnO₃ sample and the maximum figure of merit coefficient ZT of sample LaSr_1.9Ag_0.1Mn₂O₇ is 1.56×10^-5 in 390 K .3. The sample seeback coefficient passes through one process from negative to positive, moreover, transition temperature is about 300 K. In high temperature area, the small polaron seriously affect seeback coefficient; In the low temperature area, the seeback coefficient is the electronic - phonon contribution.4. Metal Ag compared to sample conductivity is biger than sample, disseminates in the substrate the metal pellet transfusion effect and the special interfacial effect can enhance the sample conductivity. Moreover, metal Ag is the heavy ion in the perovskite structure which reduces the sample heat conductivity. The result indicated that compound materials' conductivity increases then reduces with the Ag compound quantity variation. When sample Ag content is 0.05, the conductivity is biggest, which is 59523.8Sm^-1 and approximately 47 times than the sample La_0.67Sr_0.33MnO₃. When the Ag quantity is small;, the very few Ag ion enters in the lattice structure, but the Sr content reduction intensified the lattice vibration, which causes the crystal lattice vibration heat conductivity to increase, the Ag quantity further increases, some part of Ag ion enters in the lattice structure, reduced the hot lattice vibration.This article research is of great value in the oxide compound thermoelectric material's development and guiding certainly practical. From now on again, we may obtain the sample with uniting the sol - gel and the PLD technologys to enhance the thermoelectric material the performance .