Solid-Phase Synthesis of High-Entropy Crystals with the Magnetoplumbite Structure in the BaO–Fe2O3–TiO2–Al2O3–In2O3–Ga2O3–Cr2O3 System

Abstract

The present study, in the context of general research of multicomponent oxide phases with high configuration entropy of mixing, aims at investigation of possibilities of multicomponent phaseproduction with the magnetoplumbite structure by the solid-phase synthesis in the BaO–Fe₂O₃–TiO₂–Al₂O₃–In₂O₃–Ga₂O₃–Cr₂O₃ system.

The batch for the sample synthesis conformed to formulas: BaFe₂Ti₂Al₂In₂Ga₂Cr₂O₁₉, BaFe₄Ti_1,6Al_1,6In_1,6Ga_1,6Cr_1,6O₁₉, BaFe₆Ti_1,2Al_1,2In_1,2Ga_1,2Cr_1,2O₁₉.

The experiments were carried out with the use of the following reagents: BaCO₃, Fe₂O₃, TiO₂, In₂O₃, Cr₂O₃, Ga₂O₃, Al₂O₃with analytical grade of purity or better.

The study of the samples obtained by sintering of the preground and thoroughly mixed multicomponent batch at 1350 °С for 5 hours in the air atmosphere, by the X-ray phase analysis has demonstrated the possibility of formation of microcrystals with the necessary composition and structure. The presented data show that a stable multicomponent crystal structure of magnetoplumbite type can be obtained in the BaO–Fe₂O₃–TiO₂–Al₂O₃–In₂O₃–Ga₂O₃–Cr₂O₃ system even in the case when the value of configuration entropy of mixing within a sublattice formed by Fe, Ti, Al, In, Ga, and Cr, is somewhat lower than 1.5R.

The average composition of high-entropy phases in the obtained samples can be described by formulas:BaFe_2,70Ti_0.67Al_1,69In_1,61Ga_2,66Cr_2.67O₁₉, BaFe_4,56Ti_0.86Al_1,66In_1,27Ga_1,94Cr_1.71O₁₉, BaFe_6,06Ti_1.08Al_1,20In_1,16Ga_1,25Cr_1,25O₁₉.

The data testify that at the experimental conditions a noticeable fraction of titanium in not transferred into the high-entropy phase. It is necessary to take into account during the following experimental research in production of homogeneous samples of the synthesized phases for investigation of their electric and magnetic characteristics.