Comparative Thermal Insulation Nature of Ca2FeMnO6-δ and Sr2FeMnO6-δ

Abstract

We investigated the utility of Ca2FeMnO6-δ and Sr2FeMnO6-δ as materials with low thermal conductivity, finding potential applications in thermoelectrics, electronics, solar devices, and gas turbines for land and aerospace use. These compounds, characterized as oxygen-deficient perovskites, feature distinct vacancy arrangements. Ca2FeMnO6-δ adopts a brownmillerite-type orthorhombic structure with ordered vacancy arrangement, while Sr2FeMnO6-δ adopts a perovskite cubic structure with disordered vacancy distribution. Notably, both compounds exhibit remarkably low thermal conductivity, measuring below 0.50 Wm-1K-1. This places them among the materials with the lowest thermal conductivity reported for perovskites. The observed low thermal conductivity is attributed to oxygen vacancies and phonon scattering. Interestingly as scanning electron microscopy images show the smaller grain size, our findings suggest that the creation of vacancies and lowering the grain size or increasing the grain boundaries play a crucial role in achieving such low thermal conductivity values. This characteristic enhances the potential of these materials for applications where efficient heat dissipation, safety, and equipment longevity are paramount.