Crystal Structure and Anomalous Sintering Behavior of (Sr0.7 La0.3 )1−x TiO3+δ Perovskites (0 ≤ x ≤ 0.12) Synthesized by the Pechini Method

Abstract

The crystal structure, phase relationship and sintering characteristics of (Sr0.7 La0.3 )1−x TiO3+δ perovskites (0 ≤ x ≤ 0.12) have been studied using the Pechini method. High-temperature neutron diffraction analysis showed that (Sr0.7 La0.3 )TiO3+δ has an orthorhombic structure at room temperature and a cubic structure at 450 °C. (Sr0.7 La0.3 )0.88 TiO3+δ showed a single perovskite phase and other samples with an A-site deficiency of 0 ≤ x ≤ 0.08 included secondary Ruddlesden-Popper phases. Sintering characteristics improved as the A-site deficiency increased and it was found that during sintering, (Sr0.7 La0.3 )0.88 TiO3+δ expanded anomalously between 1400 °C and 1500 °C and for holding times between 0 h and 10 h at 1400 °C and 1500 °C. Additionally, observation of the samples by scanning electron microscopy showed that this expansion was caused by pore formation within the samples. All the samples showed a weight decrease at temperatures ≥1000 °C and the temperature at which oxygen release began rose as the A-site deficiency increased. The release of oxygen is likely to be related to pore formation.