CERAMICS INTERNATIONAL Available online at www.sciencedirect.com Ceramics International 40 (2014) 16141–16146 Sol–gel combustion synthesis of Zr-doped BaTiO 3 nanopowders and ceramics: Dielectric and ferroelectric studies M. Aghayan a , A. Khorsand Zak b,c,n , M. Behdani a , A. Manaf Hashim c a Department of Physics, Faculty of Science, Ferdowsi University of Mashhad, Mashhad, Iran b Nanotechnology Laboratory, Esfarayen University of Technology, Esfarayen 96619-98195, North Khorasan, Iran c Malaysia-Japan International Institute of Technology, Universiti Teknologi Malaysia, Jalan Semarak, 54100 Kuala Lumpur, Malaysia Received 18 June 2014; received in revised form 8 July 2014; accepted 8 July 2014 Available online 15 July 2014 Abstract The dielectric and ferroelectric properties of the ceramic system, Ba(Ti 1 x ,Zr x )O 3 , were investigated for compositions 0 rx r0.2. The primary nanopowders were synthesized using a sol–gel combustion route to obtain the homogenous compounds. X-ray diffraction patterns demonstrated that there was a cubic structure for the prepared nanopowders. The nanopowders were pressed into pellet form and sintered at 1250, 1300, and 1350 1C. The results revealed a significant increase in the permittivity of the Zr-doped samples. The sample showed the best dielectric properties and a ferroelectric behavior for the value of x ¼ 0.05. & 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved. Keywords: BaTiO 3 ; Barium titanate; Nanoparticles; Nanopowders; Dielectric 1. Introduction Barium titanate (BaTiO 3 ) is an environment-friendly dielectric and ferroelectric materials with similar performance as many Pb-based electro-ceramics [1]. Due to its high dielectric constant, it is widely utilized to manufacture electronic components such as multilayer ceramic capacitor (MLCC), Micro-Electro Mechanical Systems (MEMs), Dynamic Random Access Memories (DRAM), PTC thermistors, piezoelectric transducers, and a variety of electro- optic devices [2–4]. Micrometer BaTiO 3 undergoes a paraelectric to ferroelectric phase transition at about T c =130 1C, which is accompanied by a sharp peak in the permittivity curve. Above the Curie temperature, the structure of barium titanate is cubic and paraelectric. Below the Curie point, the structure is slightly distorted and three ferroelectric phase with nonzero dipole moment exist depending on temperature. The tetragonal is stable between  10 1C and 130 1C. Below 10 1C the structure becomes orthorhombic and a further transition to rhombohedral structure occurs at  80 1C [5]. In tetragonal phase, the ratio of the lattice constant (c/ a) has been shown to decrease as the particle size decreases [6]. Therefore, by controlling the grain size, the dielectric and ferroelectric properties of the ceramics will be changed. It was found that the dielectric permittivity is increased by the grain size decreases [7]. Using nanopowders as source to prepare ceramics pellet is one of the ways to control the growing of the ceramics grains. So the grain size of ceramic layer should be controlled to be small enough. Since the permanent polarization disappears above the Curie temperature, the control of T c in ferroelectric materials is of great importance for practical applications [8]. Recently, Ba (Zr x Ti 1x )O 3 (BZT) has been chosen for the fabrication of ceramic capacitors because Zr 4 þ is chemically more stable than Ti 4 þ [9]. In addition, Zr-substitution at Ti-site has been found to be an effective way to decrease the Curie temperature and exhibited several interesting features in the dielectric behavior of BaTiO 3 ceramics [10] . The nature of the ferroelectric phase transition at the Curie temperature T c of BZT is known to change strongly with the Zr content. At higher Zr contents (x 40.08), BZT ceramics show a broad dielectric constant-temperature curve near T c ; caused by www.elsevier.com/locate/ceramint http://dx.doi.org/10.1016/j.ceramint.2014.07.045 0272-8842/& 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved. n Corresponding author. Tel.: þ60 162017558, þ98 9155021785. E-mail address: alikhorsandzak@gmail.com (A. Khorsand Zak).