Jaiban et al. Nanoscale Research Letters 2012, 7:45 http://www.nanoscalereslett.com/content/7/1/45 mixed-oxide method. The starting materials used in this study were ZrO2 (99%, Riedel-de Haën, Sigma-Aldrich Corporation, St. Louis, MO, USA), TiO2 (99%, Riedel-de Haën), Bi2O3 (98%, Fluka, Sigma-Aldrich Corporation, St. Louis, MO, USA), and Na2CO3 (99.5%, Riedel-de Haën). The mixtures of oxides were ball milled in etha- nol for 24 h. The mixed powders were dried at 120°C for 24 h and then calcined in a closed alumina crucible at a temperature of 800°C for 2 h with a heating/cooling rate of 5°C/min. After sieving, a few drops of 3 wt.% polyvinyl alcohol binders were added to the mixed pow- ders which were subsequently pressed into pellets with a diameter of 10 mm using a uniaxial press with 1-ton weight for 15 s. Binder removal was carried out by heat- ing the pellets at 500°C for 1 h. These pellets were then sintered at 950°C for a 2-h dwell time with a heating/ cooling rate of 5°C/min on a covered alumina plate. The sintered samples were polished using sandpaper and cleaned using an ultrasonic bath. After that, phase identification of ceramics was investigated in a 2θ range of 20° to 80° using an X-ray diffractometer [XRD] (Phil- lip Model X-pert, PANalytical B.V., Almelo, The Neth- erlands). For a microstructural observation, the sintered pellets were polished using sandpaper as well as alumina slurry and cleaned in the same ultrasonic bath. Then, the polished samples were etched at a temperature of 800°C for 15 min with a heating/cooling rate of 5°C/min on a covered alumina plate. Microstructure of etched materials was observed using a backscattered-electron mode of a scanning electron microscope [SEM] (JSM 6335F, JEOL Ltd., Akishima, Tokyo, Japan). Numerical detail of the lattice parameters of all sam- ples was obtained from fitting between observed reflec- tion angles of experimental XRD patterns and calculated angles using the Powder Cell Software (BAM, Berlin, Germany) [7]. Measurement of grain size was performed by employing a linear intercept method on SEM images. For dielectric property measurements, the sintered sam- ples were polished by sandpaper until the thickness was approximately 1 μm. Subsequently, two parallel surfaces of polished ceramics were painted with a silver paste for electrical contacts. Dielectric constant and loss were measured at room temperature with measured frequen- cies of 1, 10, and 100 kHz using a 4284A LCR meter (Agilent Technologies Inc., Santa Clara, CA, USA). Results and discussion Figure 1 presents XRD patterns of Bi0.5Na0.5Zr1-xTixO3 ceramics where x = 0.3, 0.4, 0.5, and 0.6. All composi- tions exhibited a perovskite structure and complete solu- bility. As observed, peaks in XRD patterns shifted to higher reflection angles when Ti addition increased. The analysis indicated that Ti4+ could diffuse successfully into the BNZ lattice to form desired solid solutions. Smaller Page 2 of 5 Figure 1 X-ray diffraction patterns of BNZT ceramics. The samples were sintered at 950°C; (a) 2θ = 20° to 80° and (b) 2θ = 50° to 60°. ion of Ti4+ (0.605 Å) substituting a larger host ion of Zr4 + (0.72 Å) [8] at the B-site of the BNZ perovskite material resulted in a decrease in volume of its original unit cell. This therefore caused the patterns to shift to the right. Besides, modification by adding more than 0.4 mole frac- tion of Ti4+ changed the crystal system from an orthor- hombic prototype structure to another structure. The feature of the changed patterns was in agreement with the rhombohedral structure of BNT at room temperature (ICSD file no. 28-0983). The presence of the rhombohe- dral structure was believed to be a Ti-rich composition in the BNZ-BNT phase diagram. Observed planes in the 2θ range of 50° to 60° include (321), (042), and (300) as shown in Figure 2b. For a Ti4+ amount of 0.3 mole frac- tion, the BNZT ceramic maintained the orthorhombic structure with splitted peaks, i.e., (321) and (042). Subse- quently, the existence of a single peak (300) was found for the composition where x = 0.4. The orthorhombic to rhombohedral phase transition was then presumed to occur at a Bi0.5Na0.5Zr0.6Ti0.4O3 composition at room temperature. This was influenced by the distortion of the crystal lattice because Ti4+ occupied at the Zr4+ site. The phase transition for the Zr/Ti ratio (0.6:0.4) found in this study was in agreement with the previous report of Yamada et al. [6] who mentioned that the approximate phase transition point of the BNT-BNZ binary system was at a Zr/Ti ratio of 0.6:0.4. Quantitative data of lattice parameters obtained from the comparison between the observed and calculated reflection angles with a selected d-spacing are also given in Table 1. Thus, as a result, an isovalent substitution of Ti ion not only reduced the unit cell dimension, but also promoted the phase transition at the composition of Bi0.5Na0.5Zr0.6Ti0.4O3. SEM-BEI images of Bi0.5Na0.5Zr1-xTixO3 ceramics, where x = 0.3, 0.4, 0.5, and 0.6, are shown in Figure 2. All compo- sitions produced similarly shaped crystalline grains. The images also showed that the average size of grains decreased slightly with an increase of the Ti content up to