Indian Journal of Engineering & Materials Sciences Vol. 14, February 2007, pp. 64-68 Electrical and dielectric properties of double doped BaTiO 3 Md A Mohiddon a , P Goel a , K LYadav a , M Kumar b & P K Yadav b a Smart Materials Research Laboratory, Department of Physics, Indian Institute of Technology, Roorkee 247 667, India b Department of Physics, Meerut College, Meerut 250 001, India Received 1 May 2006; accepted 18 October 2006 Alkali (Li, Na, K) and lanthanum doped barium titanate has been prepared by solid-state reaction method. X-ray diffraction studies suggest the compound is in tetragonal phase with small change in c/a ratio. Detailed studies of dielectric constant as a function of temperature (40-300°C) and frequency (100 Hz-1 MHz) suggest that the compounds do not have relaxor behaviour and undergoes diffuse type of phase transition. Curie temperature is found to be independent of type of alkali doping and measuring frequency. However, maximum dielectric constant and resistivity are found to be strongly dependent on frequency and type of doping. IPC Code: G01R27/26, G01N33/38 Since the discovery of high permittivity (ε r ) of ferroelectric barium titanate (BaTiO 3 ) in 1943, ceramic materials based on this compound are utilized in the manufacture of electronic components, such as multilayer ceramic capacitors (MLCs), PTC thermistors, piezoelectric transducers, microwave devices and a variety of electro-optic devices 1 . Because of people’s demands, dielectric (essentially non-conducting) characteristics of ceramic materials are increasing rapidly, at the same time researchers are attempting to reduce the size of all communication devices as small and as light as possible. Due to this trend, high dielectric constant material such as barium titanate nowadays becomes more and more important in ceramic world. The permittivity of BaTiO 3 ceramic strongly depends upon the grain size. Coarse grained ceramic of pure BaTiO 3 having grain size 20-50 μm, show ε r ≈ 1500-2000 at room temperature 2 . Several other investigators 3,4 observed higher values ε r ≈ 3500-4000 in dense, fine-grained BaTiO 3 ceramic having 1 μm grain size. By adding oxide group softeners, hardeners and stabilizers one can modify the properties of BaTiO 3 ceramic. Softeners (donors) reduce the coercive field strength, elastic modulus; aging effects and increases the permittivity and dielectric constant 5 . Undoped BaTiO 3 is a high insulator material, but on doping with donors it turns into semiconductor and shows an electrical resistivity jump by several orders of magnitude at Curie temperature. In this paper, the effect of double doping on structural and dielectric properties of BaTiO 3 has been reported. Experimental Procedure The compositions Ba 0.99 (La 0.5 D 0.5 ) 0.01 TiO 3 where D = Li, Na, K were prepared by solid state reaction method, using analytical grade reagents BaCO 3, Li 2 O 3, Na 2 CO 3 , K 2 CO 3 and TiO 2 as starting materials. The stoichiometric amounts of individual reagents were homogeneously mixed in an agate mortar with acetone media to achieve a fine powder. The well- mixed powder was then calcined at 1000°C for 2 h, in alumina crucible. Calcined powder was pressed into cylindrical pellets of 1-2 mm thick and 7 mm diameter at a pressure of ~ 19×10 6 N/m 2 , using uniaxial hydraulic press. These pellets were then sintered at 1100°C for 2 h. Crystal structure and phase identification of sintered pellets was carried out by X-ray diffractometer (Brueker D8 Advance) using Cu-K α radiation (λ=1.5418 Å) and microstructure was analyzed by using scanning electron microscope (LEO 435 VP). Lattice parameters were also calculated and refined using least square method. Sintered pellets were polished and flat surface were coated with high purity silver paste and then dried at 120°C for 30 min, before taking electrical measurements. Dielectric measurements were conducted on an automated HIOKI 3532-50, LCR meter. Dielectric permitivities were acquired in the frequency range 100 Hz-1 MHz as a function of