Abstract
High-quality Ca0.8Dy0.2MnO3 nano-powders were synthesized by the solution combustion process. The size of the synthesized Ca0.8Dy0.2MnO3 powders was approximately 23 nm. The green pellets were sintered at 1150-1300°C at a step size of 50°C. Sintered Ca0.8Dy0.2MnO3 bodies crystallized in the perovskite structure with an orthorhombic symmetry. The sintering temperature did not affect the Seebeck coefficient, but significantly affected the electrical conductivity. The electrical conductivity of Ca0.8Dy0.2MnO3 increased with increasing temperature, indicating a semiconducting behavior. The absolute value of the Seebeck coefficient gradually increased with an increase in temperature. The highest power factor (3.7 × 10-5 Wm-1 K-2 at 800°C) was obtained for Ca0.8Dy0.2MnO3 sintered at 1,250°C. In this study, we investigated the microstructure and thermoelectric properties of Ca0.8Dy0.2MnO3, depending on sintering temperature.
Highlights
Solid-state thermoelectric power generation based on Seebeck effects has potential applications in waste-heat recovery
The densities of Ca0.8Dy0.2MnO3 sintered at 1150, 1200, 1250, and 1300° C are 81.5, 87.2, 98.5, and 96.3% of the theoretical density, respectively
A fine-grain size and high density are obtained even at a low sintering temperature of 1250 and 1300°C. This indicates that nano-sized powders synthesized by the glutamic acid-assisted combustion method allow for dense and fine-grained pellets at much lower sintering temperature, compared to conventional solid-state reaction processed powders
Summary
Solid-state thermoelectric power generation based on Seebeck effects has potential applications in waste-heat recovery. The efficiency of thermoelectric devices is determined by the materials’ dimensionless figure-of-merit, defined as ZT = sa2/T, where s, a, , and T are the electrical conductivity, Seebeck coefficient, thermal conductivity, and absolute temperature, respectively. The electrical transport properties of (Ca0.9M0.1)MnO3 (M = Y, La, Ce, Sm, In, Sn, Sb, Pb, and Bi) have been studied, and reported that partial substitution for the Ca led to a significant increase in the electrical conductivity, along with a moderate decrease in the absolute value of the Seebeck coefficient, thereby improving the dimensionless figure-of-merit [3].
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