Tetragonal to cubic phase transition in Sr0.75Ba0.25HfO3

HOROWITZ CLAUDIO; ALONSO ROBERTO; LÓPEZ GARCÍA ALBERTO; LAMAS DIEGO; CANEIRO ALBERTO

FERROELECTRICS

Taylor & Francis

Año: 2002 vol. 269 p. 117 - 122

0015-0193

Using powder X-Ray Difraction and Perturbed-Angular-Correlation Spectroscopy, the crystal structure and the hyperfines interaction at 181Ta probe in Sr0.75Ba0.25HfO3 have been studied. A tetragonal (I4/mcm) to cubic (Pm3m) phase transition was observed. A two-phase fiel region, where the tetragonal and cubic phases coexist, was found between 673 and 923 K. The sping precession curves were measured from room temperature up to 1373 K. A static, asymmetric and disordered electric field gradient model was used to fit this time espectra. The hyperfine parameters corresponding to the tetragonal structure changed as the temperature increase: q diminishes,  is almost constant and  diminishes. The interaction was observed to be unique up to 673 K. Above this temperature, a second interaction appeared and these two phases coexist up to 923 K. Above this temperature, the hyperfine parameters corresponding to the cubic structure was only observed. The tetragonal to cubic transformation is characterized by an activation energy of about 0.62 eV.