Microstructural characterization and spark plasma sintering of BaTiOɜ based thermistors

Barium titanate is one of the most important and widely studied ferroelectric ceramics with ABO3 type perovskite structure. Due to its promising ferroelectric properties, it has been used in several applications such as positive temperature coefficient resistors (PTCR) called thermistor, sensors, electro-optical devices, multi-layer ceramic capacitors (MLCCs), electroluminescent panels, etc. Barium titanate shows a significant phase transition below and above Curie temperature (120 °C for pure barium titanate) from tetragonal to the cubic crystal structure. This phase transition however is strongly dependent on the microstructural properties such as density, grain size distribution, type of dopants and sintering conditions. In this research, extensive characterization techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, electron backscattered diffraction (EBSD), and energy dispersive X-ray spectroscopy (EDX) were used to study the microstructural and compositional characteristics of 8 industrial samples. We have employed state of the art spark plasma sintering that offer rapid consolidation of powders, enabling significantly improved or even completely novel materials on barium titanate samples containing Ca, Sr and Pb as a dopant. The effect of various sintering parameters e.g. sintering temperature, soaking time and heating rate on microstructural and phase composition of the sintered samples were investigated and compared to the benchmark industrial sample.