Synthesis and Characterization of Perovskite Titanate for Energy Applications

Abstract

Thermoelectric materials are now receiving increasing attention as an alternative sustainable energy harvesting technology, since they can convert waste heat into useful electricity. Recently, perovskite oxides have been drawing increasing attention on thermoelectric materials due to their non-toxicity and oxidation resistance over high temperature range. In this project, two types of perovskite oxides were investigated as a potential thermoelectric material. Firstly, lanthanum titanate was prepared using sol-gel method followed by either the Conventional Sintering (CS) method or the Spark Plasma Sintering (SPS) method. Both the La-site vacancy and the oxygen vacancy were introduced. The thermoelectric properties of the CS-synthesized La2/3TiO2.87 ceramics possessed a ZT value of 0.18 at 973 K with corresponding Seebeck coefficient, and electrical resistivity of -192 μV/K and ~91 μΩm, respectively, as well as a thermal conductivity of 2 W/m K. In comparison, the nanostructured La2/3TiO2.87 ceramics using the SPS method possessed a suppressed electrical resistivity owing to the decreased amounts of large pores. The Seebeck coefficients of the CS-synthesized and SPS-synthesized La2/3TiO2.87 ceramics were independent to the porosity. The thermal conductivity was lower for the CS-synthesized La2/3TiO2.87 ceramic, as a result of the increased heat scattering of phonons by large pores. Overall, using the SPS method, the La2/3TiO2.87 ceramic achieved a more than 20% improvement on the ZT value of 0.22 at 973 K, mainly attributed to the lower electrical resistivity. Another perovskite oxide, barium titanate, was synthesized via the hydrothermal approach. The morphology of BaTiO3 particles were controlled in nanocubes and the size was tailored by the reaction time from 24 hrs to 72 hrs. The photocatalytic activities of the BaTiO3 nanocubes were evaluated under the UV-vis irradiation. The sample synthesized for 48 hrs possessed the most efficient degradation of Methylene Blue due to the optimum size and morphology. In summary, for the first time, the high-temperature thermoelectric properties of lanthanum titanate were reported and investigated. The enhancement of its thermoelectric performance was also studied. The results indicated that lanthanum titanate can be a potential material for high temperature thermoelectric power regeneration.