L Journal of Alloys and Compounds 311 (2000) 181–187 www.elsevier.com / locate / jallcom Mechanical activation synthesis and dielectric properties of 0.48PFN–0.36PFW–0.16PZN from mixed oxides * Ang Seok Khim, John Wang , Xue Junmin Department of Materials Science, Faculty of Science National University of Singapore, Singapore 119260, Singapore Received 4 June 2000; accepted 30 June 2000 Abstract Nanocrystalline 0.48PFN–0.36PFW–0.16PZN phase of perovskite structure was successfully prepared via mechanical activation of mixed oxides of PbO, Fe O , WO , Nb O and ZnO for more than 15 h at room temperature. The powder derived from 20 h of 2 3 3 2 5 mechanical activation exhibits a particle size in the range of 10–20 nm. It undergoes decomposition upon heat treatment to pyrochlore phase before a single perovskite phase was developed at the sintering temperature of 8208C for 45 min. The sintered ceramic exhibits a density of |98% theoretical density and a maximum dielectric permittivity of |9357 at the Curie temperature of |278C measured at a frequency of 100 Hz.  2000 Elsevier Science S.A. All rights reserved. Keywords: 0.48PFN–0.36PFW–0.16PZN; Mechanical activation; Dielectric properties; XRD 1. Introduction when sintering is carried out at above 8008C for 1 h [2]. The formation of these secondary phases was attributed to The solid solutions of Pb(Fe Nb )O – the preferential reactions between the oxides involved [2]. 1/2 1/2 3 Pb(Fe W )O –Pb(Zn Nb )O (abbreviated as Natarajan and Dougherty [5] reported recently that the 2/3 1/3 3 1/3 2/3 3 PFN–PFW–PZN) of perovskite structure have been recog- maximum dielectric permittivity of 0.48PFN–0.36PFW– nized as suitable materials for multilayer ceramic 0.16PZN synthesized through the conventional solid state capacitors because of their low firing temperatures below reaction was |8800 when measured at a frequency of 1 9008C, high dielectric constants and low dielectric losses kHz. [1,2]. Yonezawa [1,3] investigated widely into these com- Pioneered by Benjamin [10], mechanical alloying (MA) positions and reported that the composition of 0.48PFN– was originally devised for synthesizing alloys and inter- 0.36PFW–0.16PZN exhibited many of the most desirable metallics. It has recently been modified to synthesize properties required for a number of applications. It was functional ceramics, whereby the starting compositions subsequently employed as dielectrics in multilayer ceramic were subjected to a significant refinement in particle and capacitors [4]. crystallite sizes, together with a degree of amorphization, Unlike the synthesis of many other lead-based relaxor prior to the nucleation and growth of the designed ceramic ferroelectrics whereby several processing routes have been phases [11]. Several lead-based electroceramics have been explored, previous studies made on this ternary system prepared in the authors’ laboratory by mechanically ac- were based on the conventional ceramic processing route tivating the constituent oxides, including PMN [11], [1,2,5–7]. The five constituent oxides are mixed in a ball PMN–PT [12], PZT [13] and PZN [14,15]. As the mill, calcined at around 7508C, before the powder com- mechanical activation of mixed oxides resulted in the pacts were subjected to sintering at |8508C, resulting in formation of nanocrystalline perovskite phases at room either a single perovskite phase or a mixture of perovskite temperature, the multiple steps of calcination at high and pyrochlore phases [2,5,8,9]. Furthermore, varying temperatures commonly employed in conventional ceramic amounts of other secondary phases, such as lead tungstate processing routes for phase formation of these electro- (Pb WO ) and zinc ferrite (ZnFe O ), were also detected ceramic materials were skipped. The activation-derived 2 5 2 4 electroceramics exhibit a refined microstructure, high sintered density, and therefore excellent electrical prop- *Corresponding author. Tel.: 165-8-74-2958; fax: 165-7-76-4604. E-mail address: maswangj@nus.edu.sg (J. Wang). erties. In more recent studies, attempts were made to 0925-8388 / 00 / $ – see front matter  2000 Elsevier Science S.A. All rights reserved. PII: S0925-8388(00)01117-8