Preparation and characterization of K0.5Bi0.5TiO3 particles synthesized by a stirring hydrothermal method

Nanoparticles of potassium bismuth titanate K0.5Bi0.5TiO3 (KBT) with an average particle size of 38 nm were prepared using a stirring hydrothermal method. The pure KBT was obtained in 8 h reaction time instead of 24–48 h for conventional hydrothermal method. X-ray diffraction, Raman spectroscopy and TG analysis were used to check the proportion of hydroxyl group existing into the crude and the calcined KBT. A Hydroxyl group was found to affect the crystallite structure parameters and cell volume. When temperature increases from 25 to 1050 °C, the tetragonal structure presents a c/a ratio which decreases from 1.048 to 1.012. TG analysis and Raman vibration at high frequencies show that c/a is affected by hydroxyl group content below 750 °C and by potassium and bismuth vacancies above this temperature. The ceramic KBT showing a 300 nm size presents an improved εr=780 and a dielectric loss tan δ=0.062 at room temperature. Electric conductivity σac was also lowered to 10−6 (Ω m)−1 with an activation energy change at 673 K from 0.35 to 0.605 eV.