High-entropy oxides represent a modern class of materials with broad applicability, in which the configurational entropy of multiple equimolar cations stabilizes single-phase structures with unique defect chemistry and tunable functional properties. In the proposed work, a novel rare-earth high-entropy oxide with the composition (Dy,Y,Yb,Nd,Pr)O 1.5±δ was synthesized via citrate–nitrate combustion synthesis, followed by calcination in the temperature range 600-1100 °C. Thermogravimetry coupled with mass spectrometry revealed multi-stage decomposition and carbon removal, defining the temperatures required for complete oxidation of carbonaceous residues. High-temperature and ambient XRD analyses confirmed the formation of a single-phase cubic oxide with progressive crystallite growth from ∼10 to 40 nm upon calcination. Optical reflectance measurements showed a semiconducting band gap from 2.26 to 2.39 eV and Urbach energies that reflect changes in structural disorder during calcination. SEM/EDS analyses demonstrated the formation of homogeneous nanocrystals, with surface areas up to 31 m 2 ∙g -1 . The study provides a detailed description of phase evolution, defect chemistry, and disorder formation in a combustion-derived rare-earth high-entropy oxide with potential applications in the semiconductor industry.
SKALAR et al. (Sun,) studied this question.