Synthesis and characterisation of strontium bismuth titanate ceramics via high-energy mechanical milling

The processing conditions, microstructure, and dielectric properties of strontium bismuth titanate (SBT) were systematically studied. The specimen was synthesised by a mechano-chemical processing route using a planetary ball mill. It is important that the action is vigorous enough to break up loose aggregates and a fine particle size is obtained. The specimen was calcined at 800 degrees C for 4 h. The calcined samples were subjected to cold isostatic pressing (CIP) process and finally sintered at 1200 degrees C for 2 h. A relative density approximate to 90 per cent of the theoretical density was obtained. Pellets having a diameter of I cm and thickness of I mm were prepared from the sintered compacts for electrical measurements. X-ray diffraction showed that a single phase with the layered perovskite structure of SBT was formed. Morphological studies were carried out by SEM analysis. Frequency dependence of impedance can provide additional insight into mechanisms controlling the electrical response. Resonance studies were made on poled sample in the frequency range 100 kHz - 20 MHz using an impedance analyser (HP-4294A) interfaced to a computer at room temperature. Dielectric measurements in the frequency range 100 Hz-1 MHz were made using an impedance analyser (HP-4192A) interfaced to a computer and the measurements were carried out from room temperature to 550 degrees C. The ferroelectric hysteresis loop was measured using a standard ferroelectric analyser based on Sawyer-tower circuit. Elastic compliance (s(33), s(11)) coupling factor (k(33), k(31)) were also obtained. These materials can be utilised in practical applications as substitutes for lead titanate and lead zirconate titanate (PZT)-based ceramics, where high temperature applications are foreseen.