Modelagem computacional de propriedades termodinâmicas de titanato de bário e estrôncio

Abstract

Barium strontium titanate alloy, (Ba, Sr)TiO3 or BST, is a material derived from a solid solution of barium titanate (BaTiO3) and strontium titanate (SrTiO3). It has been the subject of extensive research in recent decades due to its extraordinary properties, making it suitable for a wide range of applications in electronic and optoelectronic devices. In this study, calculations of the lattice energy of the BaxSr1 –xTiO3 alloy were performed, employing three sets of interatomic parameters. These calculations were combined with the statistical method of Generalized Quasi-Chemical Approximation (GQCA) to investigate the thermodynamic properties of the BST alloy. Through this method, it was possible to determine the lattice constants of both the pure compounds and the alloy, all in their cubic phases. Additionally, curves of the free energy as a function of composition and temperature of the alloy, as well as its phase diagram, were constructed. Based on these data, it was observed that the BST alloy undergoes phase separation at low temperatures, in accordance with findings from other authors. The results indicate that the employed methodology holds promise for studying the stability of other perovskite alloys.