Determining the phase stability of luminescent materials based on the solid solutions of oxyorthosilicates (Lu_1−xLn_x)[(SiO₄)_0.5O_0.5], where Ln = La−Yb

Abstract

Objectives. This study aimed to predict the limits of substitution and stability of luminescent materials based on low-temperature modifications of solid solutions (spatial group P21/c) with lutetium oxyorthosilicates (Lu1−xLnx)[(SiO4)0.5O0.5], where Ln represents the rare-earth elements (REEs) of the La–Yb series.Methods. The V.S. Urusov’s crystal energy theory of isomorphous substitutions and a crystallochemical approach in the regular solid solution approximation were used to calculate the energies of the mixing (interaction parameters) of the solid solutions.Results. Using the V.S. Urusov’s theory, we calculated the energies of mixing (interaction parameters) in the systems under study. The dependences of the decomposition temperatures of solid solutions on the REE number and composition (x) were obtained and used to create a diagram of the thermodynamic stability of the solid solutions, allowing us to predict the substitution limits depending on the temperature or determine the decomposition temperature using the given substitution limits.Conclusions. The results of the study can be useful when choosing the ratio of components in matrices (host materials) and the amount of the activator (dopant) in the new luminescent, laser, and other materials based on low-temperature modifications of solid solutions of “mixed” REE oxyorthosilicates (Lu1−xLnx)[(SiO4)0.5O0.5].

Synthesis of Sodium-Lead Apatite Structure with the Excess and the Lack of Sodium

“…Researchers are interested in chemical materials science and solid-state chemistry due to the problem of isomorphic substitutions since they have used most modern inorganic materials as solid solutions rather than individual compounds. The size of unit cells, interatomic distances, and the distribution of crystallographic positions, the type of chemical bond, and the properties of the crystal structure can all be altered by introducing different additives and varying their amounts [1][2][3]. Apatite structures are compounds with many properties and could be used in many areas, including industrial, medical, agricultural, environmental, and other fields [4,5].…”