Temperature-driven phase transitions in SrBi2Ta2O9 from first-principles calculations

RODRIGO MACHADO; MARCELO SEPLIARSKY; M. G. STACHIOTTI

APPLIED PHYSICS LETTERS

Año: 2008

0003-6951

<!-- /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-parent:""; margin:0cm; margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman"; mso-fareast-language:ES;} @page Section1 {size:612.0pt 792.0pt; margin:70.85pt 3.0cm 70.85pt 3.0cm; mso-header-margin:36.0pt; mso-footer-margin:36.0pt; mso-paper-source:0;} div.Section1 {page:Section1;} --> The phase transition sequence of SrBi2Ta2O9 is investigated using a shell model with parameters fitted to first-principles calculations. We show that the complex interplay between polar and nonpolar instabilities leads to the presence of two phase transitions, corroborating the existence of an intermediate orthorhombic paraelectric phase. This phase is characterized by the rotation of the TaO6 octahedra around the a-axis. We show that this phase can be also detected from the dielectric response of the material. The present approach constitutes a powerful tool for a theoretical prediction of intermediate phases, not yet observed experimentally, in other Aurivillius compounds.