Journal of the European Ceramic Society 27 (2007) 4055–4059 Effect of lead content on the structure and piezoelectric properties of hard type lead titanate–zirconate ceramics C. Miclea a,∗ , C. Tanasoiu a , C.F. Miclea a , L. Amarande a , A. Gheorghiu b , I. Spanulescu b , C. Plavitu b , C.T. Miclea a , M.C. Cioangher a , L. Trupina a , A. Iuga a a National Institute for Materials Physics, Bucharest-Magurele, Romania b Hyperion University, Str. Calarasi 169, Sector 3, Bucharest, Romania Available online 28 March 2007 Abstract In the present investigation we studied the effect of lead content on a hard type ceramics starting from lack to excess PbO. Specimens of Pb x (Mn 0.017 Sb 0.033 Zr 0.48 Ti 0.47 )O 3 with 0.96 ≤ x ≤ 1.06 were prepared by conventional oxide mixing technique and sintered at temperatures between 1280 and 1350 ◦ C. In samples with lower Pb concentration the pyrochlore phase appeared, while in those with higher Pb an excess of PbO phase was detected. These phases proved detrimental for the properties of sintered ceramics. The highest values of piezoelectric properties were observed only for samples with an excess lead of about 2% sintered at 1340 ◦ C, indicating that it represents the optimum amount of PbO. For such samples, the density ρ was 7.77 g/cm 3 , the remnant polarization P r was 37 C/cm 3 the planar coupling coefficient k p was 0.57 and the charge constant d 33 was 340 pC/N. © 2007 Elsevier Ltd. All rights reserved. Keywords: PZT; PbO loss; Sintering; Piezoelectric properties; Dielectric properties 1. Introduction Solid solution of lead zirconate–lead titanate ceramics, known as PZT (Pb(Zr,Ti)O 3 compounds modified with izo or aliovalent ions, in order to improve their basic properties, have become the most important materials in an increasing range of application as sensors and transducers. Their excellent elec- tromechanical properties make them the key candidates for power ultrasonic transducers, actuators for fine displacements systems, piezoelectric motors, medical transducers for diagno- sis and ultrasonic imaging. 1 The performance requirements for transducers implies similar requirements for piezoelectric mate- rials. Hence high care must be taken in controlling the material properties by a careful control of processing factors such as composition, structure and heat treatment. One of the prob- lem encountered in obtaining high quality PZT materials is the compositional control and stability due to the fact that at high temperature, one of the basic component, PbO, volatilizes in a uncontrollably manner and so the stoichiometry of the final product is altered. 2 Some studies regarding the effect of compo- ∗ Corresponding author. Tel.: +40 21 4930047; fax: +40 21 4930267. E-mail address: cmic@infim.ro (C. Miclea). sitional fluctuations due to the PbO loss on material properties were already reported. 3,4 More recently Fernandez et al. 5 stud- ied in details the origin of the decomposition mechanism and its relationship with compositional fluctuations and the final prop- erties of an iron-doped PZT material. They suggested that the dopant incorporation into the crystalline lattice of the material represents the main phenomenon which controls the nature and evolution of foreign phases formed by PbO loss and the change of the properties of iron-doped PZT. This process is temperature dependent, being more intense at high temperature. Unfortu- nately, there is not yet known a relationship between temperature and PbO loss in PZT type ceramics, because there are many other factors of influence such as the nature and amount of other addi- tives used, 6 the samples environments (sintering atmosphere) during sintering. There are a few ways to avoid as much as possible the PbO volatilization. The usual practice is to pro- tect the samples during sintering either by covering them with a blanket of a similar presintered powder able to create a rich PbO atmosphere during sintering 7 or by tightly sealing the cru- cibles in which the samples are sintered. Another way is to add small amounts of PbO in excess to the basic composition 8–12 or to use sintering aids to lower, to some extent, the sinter- ing temperature. 13–22 Unfortunately, though helpful, neither way can provide a satisfactory solution to the problem but from the 0955-2219/$ – see front matter © 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.jeurceramsoc.2007.02.094