Relaxor ferroelectric behavior of La substituted BPZT ceramics J.K. Juneja a , Parveen Kumar b,e , Sangeeta Singh c , Chandra Prakash d, * , K.K. Raina e a Department of Physics, Hindu College, Sonepat 131001, India b Electroceramics Research Lab, GVM Girls College, Sonepat 131001, India c Department of Physics, GVM Girls College, Sonepat 131001, India d Directorate of ER&IPR, DRDO, DRDO Bhawan, New Delhi 110105, India e School of Physics & Material Science, Thapar University, Patiala 147004, India Received 9 November 2009; received in revised form 20 November 2009; accepted 21 December 2009 Available online 28 January 2010 Abstract Barium titanate (BT) based compounds have been of great importance in the fabrication of multilayer ceramic capacitors. Several substitutions are used to tailor its structural, electrical and ferroelectric properties. Substituent like zirconium (Zr) for titanium results in decrease in non- centrosymmetric tetragonal to centrosymmetric cubic phase transition temperature (Curie temperature). Whereas substituent like lead (Pb) for barium results in the increase in the Curie temperature. Here we are reporting effect of lanthanum (La) substitution on the properties of Zr and Pb co-substituted BT. The system Ba 0.80x La x Pb 0.20 Ti 0.90 Zr 0.10 O 3 with x = 0 and 0.01 was selected for study of structural and dielectric properties. Samples were prepared using solid state ceramic route. X-ray diffraction studies (XRD) were used to confirm single phase structure. Dielectric properties were studied as a function of frequency and temperature. Composition with x = 0.01 was found to show relaxor behavior. # 2010 Elsevier Ltd and Techna Group S.r.l. All rights reserved. Keywords: Dielectric properties; Barium titanate; Zirconium; Lanthanum; Relaxor behavior 1. Introduction The high dielectric constant of barium titanate (BT) and barium zirconate titanate (BZT) based electroceramics is responsible for selecting these materials for capacitor fabrication [1]. Further, these materials have potential applications in practical devices due to their good structural, electrical and ferroelectric properties. The properties can be tailored to suit specific requirements by molecular engineer- ing using substitutions at both Ba-site and Ti-site. Due to this reason these materials have attracted the attention of many researchers. Substituent like lead for Ba results in the increase in tetragonal to cubic phase transition temperature (Curie temperature) and decrease in room temperature dielectric constant. The temperature dependence of dielectric constant of lead substituted materials found to be better in comparison to pure barium titanate and undoped barium zirconate titanate. Substituent like zirconium for Ti results in the decrease in Curie temperature of the material, while increases the room temperature dielectric constant [2–6]. It is well reported in the literature that about 40 mol% Zr can be substituted for Ti. Aliovalent ions can act as donor as well as acceptors depending upon the amount of substitution. La 3+ and Sm 3+ can act as softener for a very small amount of substitution [1,7–10]. In the present work we have selected 10 mol% Zr content for the Ti and 20 mol% Pb for Ba for investigation. The present paper is focused on the study of relaxor type behavior of the Ba 0.80x La x Pb 0.20 Ti 0.90 Zr 0.10 O 3 for x = 0.01 in comparison with the non-relaxor Ba 0.80 Pb 0.20 Ti 0.90 Zr 0.10 O 3 (BPZT). 2. Experimental The samples were prepared using the solid state reaction route. The compositions Ba 0.80x La x Pb 0.20 Ti 0.90 Zr 0.10 O 3 with x = 0 and 0.01 were synthesized using AR grade BaCO 3 , PbO, La 2 O 3 , TiO 2 and ZrO 2 as starting raw materials. Appropriate amount of these raw materials were weighed and then were ball milled for 16 h by conventional ball mill with distilled water and zirconia balls as milling medium. The slurry was dried and www.elsevier.com/locate/ceramint Available online at www.sciencedirect.com Ceramics International 36 (2010) 1277–1281 * Corresponding author. E-mail address: cprakash@hqr.drdo.in (C. Prakash). 0272-8842/$36.00 # 2010 Elsevier Ltd and Techna Group S.r.l. All rights reserved. doi:10.1016/j.ceramint.2010.01.017