Debasis Dhak

Dielectric diffuseness and conductivity study of CuNb2O6 incorporated BaTiO3 synthesized by chemical route

The dielectric ceramics of BaTi1−3xCuxNb2xO3 (BTCN) with x=0.0, 0.1, 0.2, and 0.3 were prepared by chemical route with the help of soluble tartarate complexes of Ti4+ and Nb5+ ions. It was found that the substitution of Cu2+ and Nb5+ at the Ti site of BTCN ceramics caused a diffused phase transition. Discontinuous grain growth accompanied with excellent dielectric diffuseness was found with increasing concentration of substitution. The dielectric diffuseness (γ) was found to be maximum to 1.92 at the substitution of BTCN, x=0.1. The maximum solubility limit was found up to the entire composition range studied. A dielectric study of these compounds as a function of temperature suggested that with increasing substitution concentration the dielectric constant increased to maximum at x=0.3 with minimum tangent loss and the Curie temperature shifted onwards to the higher temperature side. The bulk conductivity indicated an Arrhenius-type thermally activated process. The variation of ac conductivity as a functi...

Density of states and impedance behaviour of transition metal substituted SrBi2Nb2O9 ferroelectric nanoceramics prepared by chemical process

Nanocrystalline layered perovskite Sr0.5A0.5Bi2Nb2O9 (A = Co2+, Ni2+, Cu2+) ferroelectric ceramics were synthesized through chemical process. The synthesized compounds were found to have tolerance values 0.90, 0.865 and 0.872 which are well within its limit. The electrical behaviour was thoroughly studied through impedance analysis within the temperature range between 400 °C and 500 °C after sintering the pressed pellet at 750 °C for 4h. Strong relaxation behaviour was found for Sr0.5Co0.5Bi2Nb2O9 and Sr0.5Cu0.5Bi2Nb2O9. The ac activation energy was calculated from the relaxation behaviour. All the studied samples showed grain conductivity behaviour only. The binding energy and density of states were studied with respect to temperature and frequency. The hopping behaviour was also studied and established a correlated barrier hopping model.

Synthesis and characterization of nanocrystalline LaMnO3 modified BaTiO3 ferroelectric ceramics prepared by chemical route

Nanocrystalline Ba1−3xTi1−3xLa2xMn4xO3, [x = 0.006, 0.008, 0.01 and 0.05] (abbreviated hereafter as BTLM) by chemical route. The phase formation and purity were checked by X-ray diffraction (XRD) study and transmission electron microscopy (TEM). The grain morphology after sintering was studied by scanning electron microscopy (SEM). The crystallite sizes range from 21 nm to 30 nm, while the particle size ranges between 27 nm and 38 nm. The grain size 212 nm and grain density 96.8% were found to be maximum for BTLM x = 0.05 and x = 0.01, respectively. The temperature dependence of dielectric constants was found to be more diffused and the peak value of the dielectric constant was decreased and more flat with the increase of the substituent concentration. The tangent loss was found to be decreased and reached to the minimum value of 0.032 for BTLM x = 0.05. The remnant polarization Pr, was 10 μC/cm2 for BTLM x = 0.01.

Synthesis, characterization, properties, and applications of nanosized ferroelectric, ferromagnetic, or multiferroic materials

1Department of Chemistry, Sidho-Kanho-Birsha University, Purulia, West Bengal 723101, India 2Materials Science Division, Argonne National Laboratory, Lemont, IL 60439, USA 3Electronics & Communication Engineering, Institute of Technology, Guru Ghasidas Vishwavidyalaya, Bilaspur 495009, India 4Department of Materials Science and Engineering, Seoul National University, Seoul 151-744, Republic of Korea