Preparation And Study On Modification Of CaMnO₃Matrix Thermoelectric Materials

Oxide thermoelectric materials have important application value in the field of new energy because of their oxidation resistance. CaMnO3is a promising high-temperature oxide thermoelectric materials. CaMnO3has high Seebeck coefficient, but the resistivity is high simultaneously, so the figure of merit is not high. the thermoelectric properties of CaMnO3can be well improved by doping to adjust the concentration of carriers. In this paper, different elements was doped to improve the performance of CaMnO3ceramics.In this paper, the CaMnO3powder was synthesized by using solid-state reaction method. The effects of doping on thermoelectric properties of CaMnO3thermoelectric oxide materials have been studied by A site substituting with Ce, Y and La, B site substituting with Mo, and A, B sites substituting with Pr-Cu and Ce-Cu, respectively. The thermoelectric properties of materials were tested by using the self-made thermoelectric power test equipment, commercial ZEM-3instrument and LFA457instrument, structure of the material was characterized by XRD.The results showed that the doped material remains single-phase structure, doping did not change its crystalline structure, except the lattice distortion.After A site doped with Ce, Y, La, the resistivity, Seebeck coefficient and thermal conductivity were decreased, but the output power increased. When the test temperature is973K, the power factor of Ce0.03sample is8.82×10-5W·m-1·K-2, ZT is0.08, the maximum output power was71mW, while the undoped one was14mW; the power factor of Y0.07sample was8.04×10-5W·m-1·K-2, ZT is0.08, and the maximum output power was68mW; the power factor of La0.04sample is8.60×10-5W·m-1·K-2, ZT is0.11.B site doped with Mo also improves the thermoelectric properties. The resistivity, Seebeck coefficient and thermal conductivity were decreased, when the test temperature is973K, the power factor of Mo0.02sample is1.01×10-4W·m-1·K-2, ZT is0.08. the maximum output power was68mW at the test temperature difference about600℃.Co-doping, including A-site doping with Pr, B-site doping with Cu and A-site doping with Ce, B-site doping with Cu, significantly reduces the resistivity of CaMnO3. When the test temperature is973K, the former optimal sample is Pr0.01-Cu0.05, its power factor is8.31×10-5W·m-1·K-2, ZT is0.08; the latter optimal sample is Ce0.05-Cu0.02, its power factor is1.04×10-4W·m-1·K-2, ZT is0.08.