The (RE¹_0.5RE²_0.5)₂Zr₂O₇ zirconates as a promising thermal insulating material dedicated to high-temperature applications

The research presented in the article aimed to characterise the insulating properties of rare-earth zirconates based on two types of lanthanides, differing in both the mass and diameter of the cations. All analysed systems were synthesised using the polymerised-complex method (PCM). The systems (Sm_0.5Gd_0.5)₂Zr₂O₇, (Nd_0.5Dy_0.5)₂Zr₂O₇, (Pr_0.5Ho_0.5)₂Zr₂O₇, and (La_0.5Tm_0.5)₂Zr₂O₇ were analysed. A brief characterisation of density, phase constituents, and microstructural homogeneity after different sintering variants was also presented. The laser flash method (LFA) was used to determine the thermal diffusivity and calculate the conductivity values. Three different factors significantly affect the scale of the phonon scattering phenomenon and the decrease in thermal conductivity: the density of grain boundaries, strong scattering on small-diameter cations (the RE² elements), the rattling effect, and decomposition of the single-phase system into a two-phase form. The combined effect of these phenomena allowed for the production of zirconates with extremely low thermal conductivity.