La temperatura de transición en SrxBa 1-xHfO3

ALONSO, ROBERTO; C. HOROWITZ; A. LOPEZ GARCIA

BOLETíN DE LA SOCIEDAD ESPAñOLA DE CERáMICA Y VIDRIO

SOC ESPANOLA CERAMICA VIDRIO

Lugar: Madrid; Año: 2002 vol. 41

0366-3175

In this contribution the transition temperature TC to the cubic phase in SrxBa1-xHfO3 compounds with x = 0.12, 0.25, 0.50, 0.75 and 0.88 is presented. These temperatures were deduced from the measurements of the perturbed angular correlation on tantalum probes. The purpose of this work is to study how the Sr substitution by Ba affect this temperature. The oxides BaHfO3 and SrHfO3 have at RT cubic and orthorhombic structures, respectively. The Sr-compound transform from tetragonal to cubic at TC1 ≈ 1400. From TC2 ≈ 1000K and up to TC1 the oxygen octahedra are tilted and the tilt angle decreases steadily as T approaches TC1. This rotation is originated by the interaction of strontium with oxygen because the Sr ionic radius (r Sr ≈ 1.13 Å) allows to be closer than Ba (rBa ≈ 1.35 Å). Then in SrxBa1-xHfO3 compounds a competition between the Ba-O interaction, 2.9502 Å apart and Sr-O interaction at a distance of 2.9098 Å in their respective pure compounds, is established.