Synthesis of ferroelectric perovskites through aqueous-solution techniques

Abstract

The hydrolysis of niobates in aqueous solutions has been applied to the coprecipitation of PbNb2/3Mgl/303 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 rates of addition and the nature of the precursors salts -is described. The perovskite phase appears after heating at 350~ and is obtained as a pure phase at 800~ after heat treatment for 1 h. Relaxor ferroelectric ceramics with a high dielectric constant can be obtained by sintering at 1000 ~ The process has been also applied to the synthesis of other relaxor ceramic compositions such as PZN (PbNb2/3Znl/303) and PFN (PbNbl/2Fel/203) compounds.

Effect of pH value on phase structure, component, and grain morphology of Pb(Sc1/2Nb1/2)O3 powders by precipitation method

“…He believed that maintaining pH value at 11.5-12.5 is needed to completely precipitate all components from the solution. However, high pH value will lead to the serious aggregation of the powders as-precipitated due to the electrostatic affinity of the OH À wrapped particles, which further induces the agglomeration of the calcined PSN particles [13,15]. Hence, the control of the pH value during the precipitation is an important issue to obtain mineral powder with fine particles.…”

Sequential Combination of Constituent Oxides in the Synthesis of Pb(Fe1/2Nb1/2)O3by Mechanical Activation

“…Considerable efforts have been made to enhance the dielectric properties of PFN. Several processing techniques, including solidstate reaction, 5 the columbite method, 6 sol-gel, 7 molten salt, 8 and the coprecipitation method, 9,10 have been attempted to refine the required microstrucure. However, a relatively high sintering temperature is needed for obtaining a high density and desirable dielectric properties for the materials derived from most of these processing techniques.…”

Multilayer piezoelectric devices based on PZT

“…For a 70 Ag/30 Pd electrode, the sintering temperature has to be lowered to 1130~ by (a) increasing the reactivity of powders, which also improves the properties [12]; (b) using sintering aids such as V205, to achieve a 95% d, PZT at 1000-1100 ~ [6]. Other sintering aids make lower sintering temperatures possible but give an inferior homogeneity [13] in comparison with ceramic without adding aids; and (c) improving the layer processing, by controlling electrode and ceramic thickness, delaminations and interaction between ceramic and electrode, thus preventing interdiffusion [14,15].…”