Jaiban et al. Nanoscale Research Letters 2012, 7:45 http://www.nanoscalereslett.com/content/7/1/45 N A N O E X P R E S S Open Access Influences of phase transition and microstructure on dielectric properties of Bi Na Zr Ti O 0.5 0.5 1-x x 3 ceramics Panupong Jaiban1, Ampika Rachakom1, Sukanda Jiansirisomboon1,2 and Anucha Watcharapasorn1,2* Abstract Bismuth sodium zirconate titanate ceramics with the formula Bi0.5Na0.5Zr1-xTixO3 [BNZT], where x = 0.3, 0.4, 0.5, and 0.6, were prepared by a conventional solid-state sintering method. Phase identification was investigated using an X-ray diffraction technique. All compositions exhibited complete solubility of Ti4+ at the Zr4+ site. Both a decrease of unit cell size and phase transition from an orthorhombic Zr-rich composition to a rhombohedral crystal structure in a Ti-rich composition were observed as a result of Ti4+ substitution. These changes caused dielectric properties of BNZT ceramics to enhance. Microstructural observation carried out employing SEM showed that average grain size decreased when addition of Ti increased. Grain size difference of BNZT above 0.4 mole fraction of Ti4+ displayed a significant increase of dielectric constant at room temperature. Keywords: ceramics, X-ray diffraction, electron microscopy, crystal structure, electrical properties Background Nowadays, materials possessing a diffuse phase transi- tion at high temperature are of interest because they are believed to be a promising candidate for various electro- nic devices. Examples are multilayer capacitors, detec- tors, MEMs, sensors, actuators, etc. However, high permittivity at room temperature is also significant. Recently, Lily et al. [1] have successfully fabricated and investigated a novel perovskite-type ceramic of Bi0.5Na0.5ZrO3 [BNZ] compound. They reported that the mentioned ceramic had an orthorhombic structure and a high curie temperature of 425°C. This value is rather high when compared with well-known lead-free ceramics such as BaTiO3 (130°C) [2] and Bi0.5Na0.5TiO3 [BNT] (320°C) [3]. Unfortunately, the BNZ system showed low dielectric constant at room temperature, i. e., approximately 100, 60, and 25 at a frequency of 1, 10, and 100 kHz, respectively. According to the most investigated PbTiO3-PbZrO3 [PZT] solid solution system, it was known that the dielectric constant of orthorhombic PbZrO3 compound * Correspondence: anucha@stanfordalumni.org 1Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai 50200, Thailand Full list of author information is available at the end of the article was quite low (i.e., approximately 190) [4], but the value could be enhanced to range about 400 to 800 with par- tial substitution of Ti4+ ions at the Zr4+ site within the perovskite lattice [5]. Improvement of the permittivity was attributed to the transformation of orthorhombic crystal structure to rhombohedral and tetragonal lat- tices. In this phase transformation, the Zr/Ti ratio was the main factor that specified the crystal structure of PZT ceramics. For a similar system of BNT-BNZ, Yamada et al. [6] predicted only that the phase-transition point of the phase diagram seemed to be approximately at a Zr/Ti ratio of 0.6:0.4. In addition, a study concerning Bi0.5Na0.5Zr1-xTixO3 [BNZT] ceramic from a Zr-rich composition has not been reported. Hence, the purpose of this work is to investigate influences of the occupancy of Ti4+ ions at the B-site of Zr4+ host ions with Zr/Ti ratios of 0.7:0.3, 0.6:0.4, 0.5:0.5, and 0.4:0.6 on phase transition and dielectric properties at room temperature of the orthorhombic BNZ ceramic. Methods The specimen was fabricated according to the chemical formula Bi0.5Na0.5Zr1-xTixO3, where x = 0.3, 0.4, 0.5, and 0.6. The powders were prepared by a conventional © 2012 Jaiban et al; licensee Springer. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.