Physical Characterization of K-Doped 0.9PMN-0.1PT Synthesized by an Association of the Columbite Route and the Polymeric Precursor Method A. A. Cavalheiro, J. C. Bruno, M. A. Zaghete, J. A. Varela CMDMC- Instituto de Química, UNESP, Araraquara, SP. Zip Code: 14.801-970 P.O.Box: 355 Phone: +55 16 3301-6712, Fax: +55 16 3322-7932 e-mail: albecava@bol.com.br Keywords: PMN-PT, Ceramics, Chemical Synthesis, Columbite and Rietveld Method. Abstract: The solid solution 0.9PbMg 1/3 Nb 2/3 O 3 -0.1PbTiO 3 is one of the most widely investigated relaxor ceramic, because of its high dielectric constant and low sintering temperatures. PMN-PT powders containing single perovskite phase were prepared by using a Ti-modified columbite precursor obtained by the polymeric precursor method. Such precursor reacts directly with stoichiometric amount of PbO to obtain pyrochlore-free PMN- PT powders. The structural effects of K additive included in the columbite precursor and 0.9PMN-0.1PT powders were also studied. The phase formation at each processing step was verified by XRD analysis, being these results used for the structural refinement by the Rietveld method. It was verified the addition of K in the columbite precursor promotes a slight increasing in the powder crystallinity. There was not a decrease in the amount of perovskite phase PMN-PT for 1mol% of K, and the particle and grain size were reduced, making this additive a powerful tool for grain size control. Introduction Lead magnesium niobate Pb(Mg 1/3 Nb 2/3 )O 3 is an important ferroelectric material because of its high dielectric constant [1,2]. The temperature of maximum dielectric constant (Tm) occurs at negative temperature (close to -15ºC) for pure PMN ceramic, but with the addition of PbTiO 3 (PT) it can be widely shifted to higher temperature. PT can be easily dissolved in the PMN perovskite structure, forming a perfectly crystalline solid solution [3,4]. Furthermore, the composition 0.9PMN-0.1PT is the most system frequently studied because the relaxor behavior is not suppressed besides Tm is shifted toward room temperature [5]. The main problem about making a single-phase PMN-based ceramics is the formation of detrimental pyrochlore (Py) phases. Such phases are mainly formed due to PbO volatilization during the powder synthesis or sintering process, but it can also be rise by an alteration of the powder stoichiometry [6-9]. Thus, many methodologies to synthesize lead- based ceramics without Py phase have been investigated, but the most important one is the columbite route, once it permits to obtain high amount of perovskite phase and can be successfully used to prepare Pb-based solid solutions, as PMN-PT [10-13]. The final properties of dielectric ceramics are function of the ceramic density, which depends on several parameters, as powder reactivity, green density, PbO volatilization and firing conditions. While previous studies proposed the use of additives to control the particle size and its size distribution, as K-based additive, others studies improved the powder synthesis [14-16]. Materials Science Forum Vols. 498-499 (2005) pp 669-675 Online available since 2005/Nov/15 at www.scientific.net © (2005) Trans Tech Publications, Switzerland doi:10.4028/www.scientific.net/MSF.498-499.669 All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of TTP, www.ttp.net. (ID: 128.120.194.195, University of California Davis, Davis, USA-05/02/15,01:25:17)