High-throughput screening of thermoelectric oxides and power generation modules consisting of oxide unicouples

A high-throughput screening technique has been developed and utilized in the discovery of a new n-type oxide possessing good thermoelectric properties. With this technique, 1000 samples can be prepared via a sol-gel method and their Seebeck coefficient (S) evaluated all within a day. For evaluation of S, a 'Seebeck tester' consisting of two pairs of thermocouples, a heater and a voltage meter, was developed. S values measured using the Seebeck tester more or less coincide with those using a conventional method. The validity of this technique was proven by Ca-Co-O and Na-Co-O systems. Screening ternary systems consisting of 3d transition metals using this technique showed LaNiO3 to possess the desired n-type properties. Electrical resistivity (rho) of this oxide is favourably quite low; however, S is as low as -25 muV K-1 at high temperature. To enhance the thermoelectric properties of LaNiO3, high-throughput screening was employed to examine candidates from the metal ternary systems (La1-xMxNiO3)-Ni-1 and (LaNi1-xMxO3)-O-2. Bi substitution in the (La1-xMxNiO3)-Ni-1 systems and Cu substitution in the (LaNi1-xMxO3)-O-2 systems were found to be effective for improvement of S and rho, respectively. A thermoelectric unicouple composed of p-type Ca3Co4O9 (Co-349) and n-type LaNiO3 (Ni-113) bulks was constructed. Open-circuit voltage (V,) of the unicouple reaches 100 mV at 1073 K on the hot side (T-H) with a temperature difference (DeltaT) of 500 K in air. Resistance of the unicouple (R-I) is 26 mOmega at 1073 K in air and increases with increase in temperature. The V-O values are consistent with those calculated using S values for each oxide leg. Maximum power (P-max), which was evaluated using the formula P-max = V-O(2)/4R(I), is 94 mW at 1073 K (DeltaT = 500 K) and increases with temperature. This value corresponds to a volume power density of 660 mW cm(-3).