2.2. Synthesis of barium titanate (BaTiO3) and Zr- and Sn-doped barium titanate

BaTiO3and Ba(Ti0.96SnxZr0.04-x)O3 (x = 0.020.04) nanocrystalline powders were synthesized by a combination of solid-state reaction and high-energy ball milling technique. The starting materials were analytical grade high-purity (999%) oxide precursors, BaCO3, ZrO2, TiO2 and SnO2. Stoichiometric amounts of the oxides were weighed according to nominal composition and ball-mixed for 12 h in alcohol. The mixture was dried in an oven and calcined in an alumina crucible at 1050C for 4 h in the air to yield BaTiO3, Ba(Ti0.96Sn0.02Zr0.02)O3, Ba (Ti0.96Sn0.03Zr0.01)O3, and Ba(Ti0.96Sn0.04)O3 powders. The calcined powders were ball-milled in an isopropyl alcohol as wetting medium using SPEX 8000 Mixer/Mills (60 Hz model) at room temperature for 7 h. The milling was stopped for 15 min after every 60 min of milling to cool down the system. The slurry was put in an oven and dried at 90C for 24 h. The milled powder was compacted at 5 ton to make pellets of size 15 mm in diameter and 1.5 mm in thickness using polyvinyl alcohol (PVA) as a binder. After burning off the binder (PVA), the pellets were sintered in a programmable furnace at temperatures of 1190C for 2 h in alumina crucibles.

#### 2.3. Characterization

Phase identification of calcined and sintered powders was carried out using X-ray diffractometer with monochromatic Cu-Kα radiation (λ = 1.54178 Å) under 40 kV/30 mA—over a 2θ range from 20 to 80 at a scanning rate of 2/min. The experimental densities of the samples were calculated using Electronic Densimeter MD-3005 ALFAMIRAGE. The morphological studies of the sintered sample were carried out using field-emission scanning electron microscopy (FE-SEM) (JEOL 7600F) operated at 15 kV. The polarization-electric field (P–E) hysteresis


Table 1. Precursors, purity level and manufacturers.

characteristics of the samples were determined using a Precision LC material analyzer (Radiant, U.S.A). The dielectric and impedance measurement was carried out for the sintered sample using an Agilent 4294 A Impedance Analyzer in the frequency and temperature range of 40 Hz–1 MHz and 30–400C, respectively.
