Perovskite layered materials with A₂B₂O₇ structures for high-temperature sensor applications – A comparative study

Perovskite layered materials with A₂B₂O₇ structure such as Ca₂Nb₂O₇, Sr₂Nb₂O₇, Nd₂Ti₂O₇, La₂Ti₂O₇, Sm₂Ti₂O₇ and Pr₂Ti₂O₇ possess very high Curie temperature (Tc > 1000°C). The above materials in powder form were synthesised using mixed oxide method by calcining well-mixed constituent powders between 1000°C and 1300°C for 2 h. Circular disc samples of 12 mm diameter were prepared and sintered at 1200–1450°C, with a soaking duration of 2 h. The sintered density, X-ray diffractometer, scanning electron microscope and electrical resistivity were measured for all samples. The samples experience a linear decrease in electrical resistivity from 10¹³ to 10⁵ Ω.cm as temperature increases between 100 and 900°C. In this paper, a comparative study on electrical resistivity for the above materials was carried out to determine their suitability for sensing applications at high temperatures.