A sol-gel derived 0.9Pb(Mg_1/2Nb_2/3)O₃–0.1PbTiO₃ ceramic

Abstract

Using inorganic chemicals, such as niobium pentachloride, titanium tetrachloride, lead nitrate, and magnesium nitrate, as the starting materials, 0.9PMN–0.1PT has been fabricated via a simple and low cost sol-gel processing route. A colloidal solution was first prepared by adding an aqueous lead nitrate solution into an ethanol solution of niobium and titanium chlorides. Magnesium nitrate was then mixed into the solution when chloride ions were removed by forming precipitates of PbCl₂ with the excess lead nitrate. The gelation of the colloidal solution was facilitated in the presence of a small amount of polyethylene glycol (PEG 300) at 70 °C. A fine perovskite 0.9PMN–0.1PT powder was obtained when the resulting gel was dried at 300 °C for 4 h and subsequently calcined. It was observed that the sol-gel derived precursor underwent a pyrochlore phase at 500–600 °C, prior to the formation of a perovskite single phase at a calcination temperature of 850 °C. A sintered density of ˜98% theoretical density was obtained when the fine 0.9PMN–0.1PT powder was sintered at 1250 °C for 2 h and the sintered ceramic shows a maximum dielectric constant of 26,682, together with a room temperature dielectric constant of 19,206 at 1 kHz. The superb dielectric properties are correlated to the microstructural features of the sol-gel derived 0.9PMN–0.1PT, which has been characterized using techniques such as XRD, SEM, and TEM.