Micro-Raman scattering and DC field dependent dielectric properties of BaZr x Ti 1-x O 3 relaxor ferroelectric ceramics Shanming Ke a, b , Haitao Huang* b , Huiqing Fan* a , H.L.W. Chan b , L.M. Zhou c a State Key Laboratory of Solidification Processing, School of Materials Science, Northwestern Polytechnical University, Xi’an 710072, PR China; b Department of Applied Physics and Materials Research Center, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, PR China; c Department of Mechanical Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, PR China ABSTRACT Barium zirconate titanate BaZr x Ti 1-x O 3 (BZT, x=0.25-0.55) ceramics have been prepared by traditional mixed oxide process. Dielectric and Raman scattering experiments were performed on various compositions. The evolution of Raman normal modes with increasing x suggested that BZT exhibits a variation of properties from conventional ferroelectric to relaxor with increasing Zr concentration. The DC electric field tunable behavior of the environmental friendly lead-free perovskite BZT relaxor ceramics was studied in the temperature range from 77 to 350 K. The results have been analyzed in relation to tunability and K factor (figure of merit) of the tunable dielectric materials. Keywords: BZT, relaxor ferroelectrics, dielectric property, tunability, Micro-Raman scattering 1. INTRODUCTION In recent years, electric-field tunable (i.e. the dependence of permittivity on electric field) dielectric materials have been extensively studied [1-3], due to their potential applications in phase shifters, filters, and high Q resonators, etc. Dielectric materials possessing high tunability, low dielectric loss, and desired dielectric permittivity are required for such applications. Many research efforts have been focused on the ferroelectric Ba x Sr 1-x TiO 3 (BST) and Pb x Sr 1-x TiO 3 (PST) solid solutions with some additives such as MgO or MgTiO 3 [1, 2], but their reproducibility, as well as the stability of the materials needs to be improved. BaTiO 3 -BaZrO 3 system was identified as an infinite solid solution in the 1950s [4]. The BaZr x Ti 1-x O 3 (BZT) system exhibits a pinched phase transition at x∼0.15, that is, all the three phase transitions corresponding to pure BaTiO 3 are merged into one broad peak [5]. Further increase in Zr concentration results in a ferroelectric relaxor [6]. Very recently, BaZr x Ti 1-x O 3 system has shown great potential for the application in tunable microwave devices [7, 8]. It should be emphasized that Zr 4+ is chemically more stable than Ti 4+ [9]. For BZT system, the most studied compositions for tunable materials are from x=0.2 to 0.3 [7, 8]. Although high tunability and low loss around room temperature have been reported in these compositions, high dielectric constant and high insertion loss of BZT (0.2 <x<0.3) has restricted its application in tunable microwave devices [2]. Considering that BaZrO 3 has relatively low dielectric constant (∼30), BZT ceramics with higher Zr concentration should exhibit lower dielectric constant. In the present work, BZT (x=0.25-0.55) ceramics were prepared by traditional solid state reaction method. Micro-Raman spectroscopy was performed to study the solid-solution of BZT ceramics. The dc field dependence of the dielectrics behavior of BaZr 0.25 Ti 0.75 O 3 (BZT25), BaZr 0.35 Ti 0.65 O 3 (BZT35) and BaZr 0.4 Ti 0.6 O 3 (BZT40) have been examined for potential application as microwave tunable materials. Results show very high tunability with low loss for BZT25 and BZT35, as well as high tunability with low loss and low dielectric constant for BZT35 and BZT40. *aphhuang@polyu.edu.hk ; phone 852 2766 5694; fax 852 2333 7629; hqfan3@163.com ; phone 86 88494463; fax 86 88494463; International Conference on Smart Materials and Nanotechnology in Engineering edited by Shanyi Du, Jinsong Leng, Anand K. Asundi Proc. of SPIE Vol. 6423, 64232E, (2007) · 0277-786X/07/$18 · doi: 10.1117/12.779867 Proc. of SPIE Vol. 6423 64232E-1