Study of the effect of phase formation processes on the change in optical and thermal properties of Nd2Zr2O7 ceramics with a pyrochlore structure

The paper presents the results of studies of the influence of phase formation processes with variations in annealing temperature on the processes of stabilization of the crystal structure, optical and thermal properties of Nd₂Zr₂O₇ ceramics, which have great potential for use in optoelectronic applications due to the transitions of Nd³ ions, as well as high stability to external factors with the possibility of creating transparent ceramics. During the conducted studies it was established that the stabilization temperature of the Nd₂Zr₂O₇ phase is 1100–1250 °C, at which the throughput is maximum, and the thermal conductivity coefficient is about 2.1–2.2 W/m × K. The assessment of phase transformations and changes in optical properties revealed that an elevation in the annealing temperature, leading to stabilization of the Nd₂Zr₂O₇ phase, leads to a decrease in the concentration of oxygen vacancies in the structure of ceramics; however, at temperatures above 1200 °C, the observed growth in oxygen vacancies is due to the effects of substitution of Zr⁴⁺ cations by Nd³⁺ cations, which results in formation of additional oxygen vacancies in the structure, alongside impurity inclusions in the form of a cubic phase of Zr(Nd)O₂, which is a product of phase polymorphic transformations during high-temperature annealing. Alterations in the thermophysical properties of Nd₂Zr₂O₇ ceramics are directly dependent on phase formation processes and associated changes in the concentration of oxygen vacancies, which are the determining factor influencing the heat transfer rate.