The thermal decomposition of K0.5Bi0.5TiO3 ceramics

The high-temperature behaviour of K0.5Bi0.5TiO3, prepared using a conventional solid-state reaction method, was investigated using X-ray powder diffraction, scanning electron microscopy, wavelength-dispersive X-ray spectroscopy and Knudsen effusion combined with mass spectrometry. The results revealed the formation of an off-stoichiometric matrix phase with an excess of bismuth and a deficit of potassium compared to the stoichiometric K0.5Bi0.5TiO3 during the solid-state reaction. During the thermal treatment potassium and bismuth vapours were detected over the solid sample and related to the thermal decomposition of the matrix phase. The losses of the potassium and bismuth components shifted the nominal composition to a three-phase region, and as a result, K2Ti6O13 and a new Bi-rich ternary phase were formed in the system, the latter being formed after prolonged sintering. Differential thermal analyses and heating-microscope analyses showed a narrow sintering-temperature range limited by the melting of the sample above 1040 °C.