Influence of rare-earth doping on the structural and dielectric properties of orthoferrite La0.50R0.50FeO3 ceramics synthesized under high pressure

The effect of co-doping on the structural and dielectric properties of the La0.50R0.50FeO3 orthoferrites for a full number of substitutions (R = Ce-Lu) has been experimentally and theoretically studied using X-ray diffraction, SEM, EDS, and dielectric spectroscopy methods. The La0.50R0.50FeO3 ceramics with R = Nd, Sm, Gd, Dy, and Er, prepared by a solid-state reaction method under cold pressing at high pressure P = 4 GPa, have been taken as a basis. Structural parameters in the La0.50R0.50FeO3 orthoferrites have been obtained using Rietveld re finement of X-ray experimental data with their further approximation by linear dependence. Monotonic change in crystal lattice parameters, orthorhombic distortion degree, global instability index, and Goldschmidt tolerance factor have been observed for all samples doped by different R-cations. With increase in the radius of R-cation, a growth in an average grain size has been detected. The investigation of dielectric properties in a wide frequency range of 10(-1)-10(10) Hz and their theoretical description with determining main mechanisms of dielectric polarization made it possible to establish regularities among a type of doping R-cation, crystal-chemical parameters and dielectric properties. The studied ceramic La0.50R0.50FeO3 samples demonstrate colossal dielectric constant similar to 10(4) and relatively small dielectric loss tangent in a low-frequency range. The obtained results can be useful for further application of orthoferrite-based materials as sensor and switching devices. (C) 2020 Elsevier B.V. All rights reserved.