Thermophysical Properties of Ceramics Produced from Nanocrystalline InFeZnO4 Powder

The paper discusses the results of a study of the structural and thermophysical characteristics of polycrystalline ceramics produced from the InFeZnO₄ nanoparticles. It was found that the bulk density of the resulting material is ~86% of the theoretical one. Scanning electron microscopy has shown that it has a dense microcrystalline structure consisting of randomly oriented grains with dimensions of 5–20 µm. The thermal diffusivity of InFeZnO₄ ceramics was studied using the laser flash method. It was found that as the temperature increases from 299 to 1273 K, it decreases from 1.29 to 0.44 mm²/s. Using adiabatic and differential scanning calorimetry, the temperature dependence of the heat capacity of InFeZnO₄ was studied for the first time. It was established that the measured curve has no signs of the existence of phase transitions in the range from 83 to 923 K. Using experimental data on thermal diffusivity, heat capacity, and density, an equation for the dependence describing the change in thermal conductivity of the material under study in the range from 299 to 1273 K was obtained. It was revealed that ceramics produced from InFeZnO₄ nanoparticles obtained by the polymer-salt method have a higher thermal conductivity compared to those synthesized by standard ceramic technology from a mixture of In₂O₃, Fe₂O₃, and ZnO oxides. The results obtained allow us to recommend InFeZnO₄ as a basis for the creation of thermally stable functional materials with low thermal conductivity at high temperatures.