Synthesis of ferroelectric perovskites through aqueous solutions techniques

Abstract

The hydrolysis of niobates in aqueous solutions has been studied as a function of pH and concentration. The process has been applied to the coprecipitation of PbNb2/3Mg1/3O3 leading to a low temperature synthesis of this ferroelectric relaxor ceramic. The effect of hydrolysis conditions such as the concentration of bases and acids used, their rate of addition, temperature and the nature of the precursor salts is described. The homogeneity of the precipitates has been characterized through infrared spectroscopy and X-ray diffraction techniques. The perovskite phase appears after heating at 350°C and is obtained as a pure phase above 750°C after one hour heat-treatment. Relaxor ceramics with high dielectric constant can be obtained by sintering above 1000°C. The process also has been successfully applied to the synthesis of other relaxor ceramic compositions such as PZN (PbNb2/3Zn1/3O3), PFN (PbNb1/2Fe1/2O3) as well as CdNb2O6 and MgNb2O6 compounds.