Synthesis and characterization of nanocrystalline potassium tantalum oxide by sol–gel processing

Nanocrystalline potassium tantalum oxide (KT) colloids have been synthesized using sol–gel technique, followed by the peptization and the growth of the precipitates under hydrothermal conditions. The peptization of the precipitates occurs easily by heating at 110 °C for 6 h in a 0.5 M tetramethylammonium hydroxide solution. The size of primary particles exhibiting nanometer order has been controlled by autoclaving temperature between 160 and 210 °C during the hydrothermal treatment step. X-ray diffraction and UV–vis spectrophotometer analyses show the pyrochlore phase transforms into perovskite phase at about 800 °C, which is consistent with a shift of absorption edge.