Phase Transitions and Relaxation Behaviors in Barium Strontium Titanate Ceramics Determined by Dynamic Mechanical and Dielectric Analysis

Abstract

Barium strontium titanate (Ba_1-xSr_xTiO₃) ceramics were prepared by solid-state reaction method. XRD patterns showed that BT (x = 0) and BST2 (x = 0.2) ceramics presented tetragonal phase, while BST4 (0.4) and BST6 (0.6) ceramics showed cubic phase at room temperature. The relative permittivity and dissipation factor of Ba_1-xSr_xTiO₃ ceramics with temperature of 125–425 K were characterized at 1–100 kHz by LCR meter. The Young's modulus and internal friction of Ba_1-xSr_xTiO₃ ceramics in the range of 125 K–425 K at different vibration frequencies were tested by a Dynamic Mechanical Analysis (DMA) system. Compared with the dielectric measurement, mechanical analysis was more sensitive to reflect the phase transition and relaxation process. All Ba_1-xSr_xTiO₃ samples showed three phase transitions, the transition temperatures decreased and the phase transition diffused as Sr content increased. Besides, a relaxation process caused by the interaction between domain walls and lattice defects emerged in pure BT ceramic, while it disappeared in all BST ceramics.

Keywords:

• Ba_1-xSr_xTiO_3; dielectric analysis
• DMA
• phase transition
• relaxation process

Funding

This work was supported by the National Key Technology R&D Program of China (2009BAG12A04) and the Scholarship Award for Excellent Doctoral Student granted by Ministry of Education (Nos. 0500219171).