Определение фазовой стабильности люминесцентных материалов на основе твердых растворов оксиортосиликатов (Lu1−xLnx)[(SiO4)0.5O0.5], где Ln = La–Yb

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].Цели. Целью работы явилось прогнозирование пределов замещения и стабильности люминесцентных материалов на основе низкотемпературных модификаций твердых растворов (пространственная группа Р21/с) на основе оксиортосиликата лютеция (Lu1−xLnx)[(SiO4)0.5O0.5], где Ln – редкоземельный элемент серии La–Yb.Методы. Для расчета энергий смешения (параметров взаимодействия) для твердых растворов была использована теория изоморфной смесимости В.С. Урусова и кристаллохимический подход в приближении регулярного твердого раствора.Результаты. Получены зависимости температур распада твердых растворов от порядкового номера редкоземельных элементов и состава, которые использованы для построения диаграмм термодинамической устойчивости твердых растворов, что позволило прогнозировать пределы замещения в зависимости от температуры или определять температуру распада на основе заданных пределов замещения.Выводы. Результаты исследования могут быть полезны при выборе соотношения компонентов в матрице («хозяине») и количества активатора (допанта) в новых люминесцентных, лазерных и других материалах на основе низкотемпературных модификаций твердых растворов «смешанных» оксиортосиликатов редкоземельных элементов (Lu1−xLnx)[(SiO4)0.5O0.5]

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

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]