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

Barium strontium titanate (Ba1-xSrxTiO3) 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 Ba1-xSrxTiO3 ceramics with temperature of 125–425 K were characterized at 1–100 kHz by LCR meter. The Young's modulus and internal friction of Ba1-xSrxTiO3 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 Ba1-xSrxTiO3 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.