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 degrees 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 degrees C and by potassium and bismuth vacancies above this temperature. The ceramic KBT showing a 300 nm size presents an improved epsilon(r)=780 and a dielectric loss tan delta=0.062 at room temperature. Electric conductivity sigma(ac) was also lowered to 10(-6) (Omega m)(-1) with an activation energy change at 673 K from 0.35 to 0.605 eV. (C) 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved.