JOURNALOF MATERIALS SCIENCE: MATERIALS IN ELECTRONICS 15 (2004) 671±675 Effect of doping Ca ions on structural and electrical properties of Ba(Zr 0.05 Ti 0.95 )O 3 electroceramics SHRABANEE SEN, R. N. P. CHOUDHARY Department of Physics and Meteorology, Indian Institute of Technology, Kharagpur 721302, India Polycrystalline samples of (Ba 1  z Ca z )(Zr 0.05 Ti 0.95 )O 3 z  0, 0.03, 0.06 and 0.09 (BCZT) belonging to perovskite ferroelectric were prepared by a high-temperature solid-state reaction technique. Preliminary room temperature X-ray study con®rmed the formation of a single phase compound in orthorhombic crystal structure. Detailed studies of dielectric parameters as a function of temperature at 10 kHz suggests that the substitution of Ca 2  ion at the Ba-site and Zr 4  at Ti-site has a strong effect on the dielectric properties of BaTiO 3 . # 2004 Kluwer Academic Publishers 1. Introduction Since the discovery of ferroelectric properties in BaTiO 3 [1], a large number of ferroelectric compounds with perovskite structure of a general formula ABO 3 (A  monovalent/divalent, B  tri to hexavalent ions) have been extensively studied in search of new materials for device applications. The growing interest in search of suitable materials for devices has led to the development of a large number of new complex ferroelectric ceramics with a wide variety of composition and stable structure. Some complex perovskite ferroelectric compounds prepared in a single crystal, thin ®lm and/or ceramic form are nowadays widely used for computer memory, electro-optical modulators, pyroelectric sensors and other electronic devices [2±9]. It has already been reported that ferroelectric properties of the compound BaZr 0:05 Ti 0:95 O 3 [10] formed by the addition of BaTiO 3 and BaZrO 3 showed that they have phase transition with a high-dielectric constant. It is well known that a suitable ionic substitution at different atomic sites of ABO 3 type materials has a dramatic effect on their physical properties. Substitution of both isovalent and aliovalent cations for the host ones in perovskite lattice plays a very important role in these modi®cation mechanisms [11]. In view of this, we have synthesized and studied various physical properties of a group of new compounds having a general formula (Ba 1  z Ca z )(Zr 0:05 Ti 0:95 )O 3 z  0, 0.03, 0.06 and 0.09, on which not much has yet been reported. In this paper we report the structural, dielectric and electrical properties of (Ba 1  z Ca z )(Zr 0:05 Ti 0:95 )O 3 (BCZT) z  0, 0.03, 0.06 and 0.09 compounds. 2. Experiment Polycrystalline samples of BCZT with z  0, 0.03, 0.06 and 0.09 were prepared by a high-temperature solid-state reaction technique using pure carbonates and oxides: BaCO 3 (99% M/s Glaxo Laboratories, India), CaCO 3 (98.5%, M/s Loba Chemical India), ZrO 2 (97%, M/s Loba Chemical India) and TiO 2 (99.9% M/s s.d.®ne Chemical, India). These carbonates and oxides were taken in desired stoichiometry and thoroughly mixed in wet atmosphere (methanol) in an agate mortar for 2 h, and then dried by slow evaporation. The air-dried powders of the compounds were calcined at 1150  C for 18h. The process of mixing and calcination was repeated until homogeneous ®ne powder was obtained. The calcined powder was used to make cylindrical pellets of diameter 10 mm and thickness 1±2 mm using a hydraulic press at a pressure of 6610 7 N/m 2 . Polyvinyl alcohol (PVA) was used as a binder to reduce the brittleness of the pellets. The pellets were sintered at 1250  C for 15 h in an air atmosphere. The formation of single-phase compound was checked by an X-ray diffraction (XRD) technique using an X-ray Powder diffractometer with CoK a radiation l  1.7902A Ê  in a wide range of Bragg angles 2y 20  5 2y5 100  . In order to study the electrical properties, both the ¯at surfaces of the samples were polished and electroded with high purity silver paint. All the samples were dried at 180  C for 4 h to remove moisture, if any, and then cooled at room temperature before taking any measure- ment. The dielectric constant e, tangent loss tan d was measured as a function of temperature (30±300  C) at different frequencies (100 Hz±1MHz) using a HIOKI 3532 LCR HITESTER. The d.c. resistivity was obtained as a function of temperature at a constant voltage of 10 V with the help of Keithley (model 617) programmable electrometer. 3. Results and discussion All the prominent re¯ection peaks of the XRD pattern of the samples were indexed and the lattice parameters were determined in tetragonal and orthorhombic crystal system using a standard computer package ``POWD'' [12]. On the basis of the best agreement between d obs and d cal SDd  Sd obs  d cal  minimum, a suitable unit 0957±4522 # 2004 Kluwer Academic Publishers 671