Effect of perovskite template seeds on microstructures and thermoelectric properties of Ca0.87Ag0.1Dy0.03MnO3 ceramics

Abstract

Calcium manganite (CaMnO3) ceramics, members of the perovskite family, have attracted considerable attention in the field of thermoelectric materials owing to their environmental friendliness, chemical stability, long lifetime, and low cost. Ruddlesden–Popper Ca3Mn2O7 and plate-like perovskite CaMnO3 templates were synthesized using the molten salt method. Perovskite CaMnO3 template seeds with a radius-thickness ratio of 16.8 were obtained via topochemical conversion process, demonstrating an obviously anisotropy. The template seeds were introduced into Ca0·87Ag0.1Dy0.03MnO3 ceramics to promote the grain growth. The bulk density of the sample containing 20 wt% template seeds was 96.0%. An electrical resistivity of 5.35 mΩ cm, a Seebeck coefficient of − 196 μV/K, and a power factor of 0.73 mW/m·K2 were obtained. Such enhancements in thermoelectric properties could be attributed to the formation of grain boundaries between stripe-like and equiaxial grains. Additionally, the maximum ZT value of 0.35 reached at 500 °C, which is 57% higher than that of the sample without template seeds. Therefore, it is believed that this study can lay the foundation for textured CaMnO3 ceramics with superior thermoelectric properties.