Estudo ab initio para investigar as propriedades estruturais e eletrônicas do Ba1−xCexZr1−yHfyO3

Abstract

A theoretical study was developed for a cubic structure under space group Pm3m, with lattice parameter of about 4.2 Å corresponding to the BaZrO3 Perovskite to be doped with Hf and Ce. The experimental Hf-doping is based on previous works of Fassbender et.al. [1]. In this study, the photoluminescence (PL) of BaZrO3 bulk host lattice is increased by the Hafnium addition. The Ce-doping was looking for widering of PL emission. Therefore a computational model is necessary to understand the origin of that luminescence. The replacement of cerium on Ba site generates new possible electronic transitions since that luminescence is narrow and poor. It was synthesized samples of Ce and Hf-doped BaZrO3 without addional phase detected by X-ray diffraction. Meanwhile, the PL emission disappears with 4% of cerium concentration. This unexpected result requires an additional computational approach using CRYSTAL09 [2] package to make this simulation based on All-Electron Basis Set and pseudopotentials according to the convergence criteria. Firstly, the convergence of supercell was optimized whithout Hf and Ce and subsequently for each one separately and then aproached together. Then, the Hf content promotes lattice distortions that emerges to vibrational modes to be evaluated from theoretical simulation. The same interpretation was also evaluated to Ce. This theoretical point of view is able to understand observed physical phenomena in order to predict future experimental results.