Hydrothermal synthesis of doped PZT powders: sintering and ceramic properties N. Texier Mandoki, C. Courtois * , P. Champagne, A. Leriche Lab. Materiaux Avances et Ceramiques LAMAC, Hainaut-Cambresis, Universite de Valenciennes et du UVHC, Zone Ind. du Champ de l’Abbesse, F-59600 Maubeuge, France Received 16 January 2003; received in revised form 5 March 2004; accepted 16 March 2004 Available online 10 May 2004 Abstract We present here the sintering behaviour, the ceramic characteristics and the electrical properties of PZT prepared from new hydrothermal powders. These results are compared with classical calcined ceramic properties. PZT powders are doped corresponding to the formula Pb((Zr 0.49 Ti 0.51 ) 0.94 Mn 0.0252 Sb 0.0192 W 0.0156 )O 3 with or without 0.8758 mol% Ni. D 2004 Elsevier B.V. All rights reserved. Keywords: Piezoelectric materials; Microstructure; Perovskite; Ceramic; PZT; Hydrothermal powders; Sintering; Electrical properties 1. Introduction The volatility of PbO during sintering of PZT powders can be quite serious, which leads the properties of ceramics to deteriorate and to pollute the environment. In that way, it is appropriate to develop more reactive powders to allow the making of dense and homogeneous PZT ceramics at low temperature. Hydothermal synthesis is an effective method for the production of reactive oxide powders. Generally, PZT powders are synthesised via a calcination route followed by a desagglomeration step [1,2]. High temperatures (above 1200 jC) are needed to densify PZT ceramics. At these temper- atures, the volatility of PbO during sintering is quite serious, which leads the properties of ceramics to deteriorate. That is why the lowering of the PZT ceramic sintering temperature has been studied by many authors. Different methods are reported: the use of additives to form liquid phases [3,4] and the development of the chemical powder process [1] like sol–gel [5], coprecipitation [6], hydrothermal [7,8] route which lead to fine reactive and homogeneous powders. The aim of this work is to produce PZT ceramics at low temperature for actuator applications starting from optimised chemically synthesised powders. The composition Pb((Zr 0.49 Ti 0.51 ) 0.94 Mn 0.0252 Sb 0.0192 W 0.0156 )O 3 + 0.2 wt.% NiO presents a high mechanical quality factor ( Q m ) and a high piezoelectric constant (d 33 ) [9] which are necessary for actuators. In a previous work [10], we have optimised the calcined route for this kind of products. The properties of the materials were determined and considered as a reference for the following. The sintering behaviour of the hydrothermal powders is presented here. Fully densified ceramics are obtained by sintering these powders; their electrical proper- ties are determined and compared with the reference. 2. Experimental procedure 2.1. Hydrothermal synthesis A clear solution of mixed titanium isopropoxide, zirconi- um propoxide and antimony ethoxide is prepared in isopro- panol. Once hydrolysed, the tungsten chloride solution is added and the suspension is mixed for 2 h. The precipitate is filtered to eliminate alcohol. The fresh precipitate is then redispersed in water. Aqueous solutions of lead nitrate, with an excess of 30%, and manganese nitrate are added. KOH pellets are then introduced, final KOH concentration is 1 mol l À 1 . In such a basic media, soluble Pb(OH) 4 2 À species remains and does not react to form PZT, a 30% excess is 0167-577X/$ - see front matter D 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.matlet.2004.03.019 * Corresponding author. Tel.: +33-3-2753-1660; fax: +33-3-2764- 6654. E-mail address: christian.courtois@univ-valenciennes.fr (C. Courtois). www.elsevier.com/locate/matlet Materials Letters 58 (2004) 2489 – 2493