J Integr Sci Technol, 2014, 2(1), 13-21 .Article. Journal of Integrated Science and Technology Structural analysis and dielectric characterization of Aurivillius type CaSrBi 2 Nb 2 O 9 ceramics S. Khasa, a Paramjeet Singh, b Sujata Sanghi, b Navneet Singh, b and Ashish Agarwal b* aDepartment of Physics, Deenbandhu Chhoturam University of Science & Technology, Murthal, Sonepat, Haryana, India-131039 b Department of Physics, Guru Jambheshwara University of Science & Technology, Hisar, Haryana, India-125001 ABSTRACT This work describes synthesis of powdered materials belonging to the Aurivillius oxide family (Bi2O2)2+(An- 1BnO3n+1)2- for n = 2 and provides an approach for understanding the structural evolution with composition. The effect of strontium doping on the lattice response and dielectric properties of Ca1-xSrxBi2Nb2O9 (x = 0.0, 0.5, 1.0) ferroelectric ceramics is studied. The XRD studies revealed single phase formation of orthorhombic structure. The average crystallite size was obtained in the range 22-41 nm. The dielectric properties, viz. dielectric constant, loss tangent and ac electrical conductivity of the samples were studied by using impedance spectroscopy. A strong low frequency dielectric dispersion was found to exist in these samples. Its occurrence was ascribed to the presence of ionized space charge carriers such as oxygen vacancies. The relationship among doping, crystal structure, and dielectric properties were also discussed. Measurements of the dielectric permittivity as a function of temperature reveal signs of single phase transition. The thermal activation energy for the grain electric conductivity was lower in the high temperature region (Ea(ht) = 0.08 eV) and higher in the low temperature region (Ea(lt) = 0.21 eV). Keywords: Aurivillius oxide, impedance spectroscopy, electrical conductivity, solid-state reaction. Introduction In 1950s, Aurivillius synthesized a new series of layered ceramics, which contained Bismuth layer as a structural constraint. The role of bismuth layer in influencing the electrical and ferroelectric properties of these ceramics has been found to be crucial. 1-6 Recently, capacitors based on layered perovskites such as CaBi 2 Nb 2 O 9 (CBNO) and metallic electrodes, such as Pt, have generated interest because of their negligible polarization fatigue (> 10 12 cycles), long polarization retention, and very low leakage current. 7-12 But the major limitations for the application of CBNO are the high processing temperature (~800-1000 o C) and low remnant polarization compared to the processing temperature of 600 o C for PZT ceramics. 13 The high processing temperature of CBNO makes it not easy to match the process of very-large-size-integrated circuits (VLSI) fabrication to produce high quality non-volatile memory. One of the approaches to solve the problem is to lower the CBNO processing temperature and the other is to solve the problems caused by the high processing temperature. It has been found that the thin film of CBNO demonstrates their excellent fatigue endurance and has a significant influence on the ferroelectric properties. 14, 15 The grain size of the polycrystal CBNO thin film plays an important role in improving the CBNO capacitor ferroelectric properties. It has been noticed that minimum ferroelectric properties are exhibited only when the grain approach a critical size. 15 Therefore it may be a good way to achieve a higher remnant polarization and lower processing temperature by forming solid solutions of CBNO with another ferroelectric material, which has higher remnant polarization, larger grain size and lower processing temperature. Some CBNO-based solid solutions, especially CBNO/SBTO have been studied in the past 16 but the dielectric properties of these ceramics are yet to be investigated experimentally. In the present study we have prepared solid solutions of Ca 1-x Sr x Bi 2 Nb 2 O 9 ceramics (with x = 0.0, 0.5, 1.0). These kind of ceramics belong to a family of oxides with a general formula (Bi 2 O 2 ) 2+ (A n-1 B n O 3n+1 ) 2- where, n = 1,2,3,4,5 representing the number of layers. The structure consists of (Bi 2 O 2 ) 2+ layers, made up of oxygen octahedral, interleaved with perovskite like (A n-1 B n O 3n+1 ) layers. Modification in these ceramics by doping to improve the properties of Aurivillius type of ceramics has been a matter of interest. These ceramics Received 25 July, 13 Address: Ashish Agarwal Department of Physics,Guru Jambheshwara University of Science & Technology, Hisar, Haryana, India-125001 Tel: +919416672988 Email: aagju@yahoo.com ---- Cite as: J. Integr. Sci. Technol, 2014, 2(1), 13-21 © IS Publications Journal of Integrated Science and Technology pubs.iscience.in/jist J. Integr. Sci. Technol., 2014, 2(1), 13-21 1 3