Preparation of Entropy-Stabilized Fluoride Phases of Fluorite Structure by Coprecipitation from Aqueous Solutions

Nanosized polysubstituted solid solutions, containing from three to eight di- and trivalent cations in different quantitative ratios, with the general formula $$M_{{1 - x}}^{n}R_{x}^{m}{{{\text{F}}}_{{2 + x}}}$$ , where M = Ca, Sr, Ba, Pb, R = La, Gd, Dy, Yb, n = 3 and 4, m = 0, 1, 2, and 4, and х varies from ~0.07 to ~0.3 for different cationic compositions, have been obtained by coprecipitation from aqueous solutions of nitrates. They all retain the fluorite structure (structural type CaF2, space group $$Fm\bar {3}m$$ ). The possibilities of precipitation of mixed solid solutions with different combinations of cations and using different fluorinating agents were demonstrated. It is shown that the obtained solid solutions are medium- and high-entropy phases.