Thermistor formation using BaTiO3 powders synthesised by the Pechini method

Abstract

Barium titanate (BaTiO3) is a compound of interest in the field of electroceramics which is widely used in the manufacture of capacitors, piezoelectric transducers and resistive devices having a positive temperature coefficient (PTCR) and in manufacturing pyroelectric and optoelectronic devices. Most of these devices are obtained by consolidating high purity, suitable sized particle ceramic powders; structured synthesis methods are required to ensure such requirements. BaTiO3 powders were synthesised by a polymeric precursor method (Pechini) in this work. Very pure, small particle sized, raw material was obtained. These powders were characterised using thermogravimetric and differential thermal analysis (TGDT), X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The results indicated that samples treated at 650°C presented cubic BaTiO3 as unique crystalline phase. If a sample were treated at 1,100°C, the tetragonal phase having a c/a < 1.007 relationship was the main crystalline phase. Samples treated at 1,100°C showed ferroelectric-paraelectric transition at T ≈ 123°C. BaTiO3 tetragonal ceramic powders were uniaxially pressed and then synthesised at 1,200°C for 2 hours. These samples were electrically characterised. These samples' curves of electrical resistance versus temperature (R-T) showed their PTCR thermistor behaviour. Current-voltage (IV) variation was also measured at different temperatures.