Dielectric spectroscopy characterization of relaxation process in Ni/epoxy composites

Structural, dielectric, electrical properties of Nd doped double perovskite ceramics and variation of density of states upon doping

Core‐shell structured Al/PVDF nanocomposites with high dielectric permittivity but low loss and enhanced thermal conductivity

Dielectric relaxation dynamics of Al/epoxy micro-composites

A new lead-free perovskite Ba(Bi1/2Ta1/2)O3 was prepared by conventional ceramic fabrication technique at 1,200 °C/4 h in air atmosphere. The crystal symmetry, space group and unit cell dimensions were determined from the experimental results using FullProf software. The crystallite size and lattice strain were estimated from Williamson-Hall approach. XRD analysis of the compound indicated the formation of a single-phase cubic structure with the space group Pm3m. EDAX and SEM studies were carried out in order to evaluate the quality and purity of the compound. Permittivity data showed a low temperature coefficient of capacitance (T
 CC
  < 4%) up to +125 °C. Complex impedance analyses suggested the dielectric relaxation to be of non-Debye type. Electric modulus studies supported the hopping type of conduction in Ba(Bi1/2Ta1/2)O3.

Dielectric relaxation in complex perovskite Ba(Bi 1/2 Ta 1/2 )O 3

Lead-free perovskite BaY 0.5 Nb 0.5 O 3 was prepared by conventional ceramic technique at 1375 °C/7 h in air atmosphere. The crystal symmetry, space group and unit cell dimensions were derived from the experimental results using FullProf software. XRD analysis of the compound indicated the formation of a single-phase cubic structure with the space group Pm3m. EDAX, X-ray mapping and SEM studies were carried to study the quality and purity of the compound. Complex impedance analyses suggested the dielectric relaxation to be of non-Debye type. To find a correlation between the response of the real system and idealized model circuit composed of discrete electrical components, the model fittings were presented using the impedance data. Electric modulus studies supported the hopping type of conduction in BaY 0.5 Nb 0.5 O 3 . The correlated barrier hopping model was employed to successfully explain the mechanism of charge transport in BaY 0.5 Nb 0.5 O 3 . The ac conductivity data were used to evaluate the density of states at Fermi level, minimum hopping length and apparent activation energy of the compound.

Electrical properties of BaY0.5Nb0.5O3 ceramic: Impedance spectroscopy analysis

Lead-free (1 − x)Ba(Y1/2Nb1/2)O3–xBaTiO3; (0 ≤ x ≤ 1) ceramics have been synthesized using solid-state reaction method and characterized by X-ray diffraction, scanning electron microscopy, dielectric and impedance studies. The crystal-structure of the compounds is found to be cubic with the space group Pm3m(221) except for BaTiO3 for which it is tetragonal (P4/mmm). Complex impedance spectroscopy analysis indicated the presence of non-Debye type dielectric relaxation in Ba(Y1/2Nb1/2)O3–BaTiO3 system. Compound 0.25Ba(Y1/2Nb1/2)O3–0.75BaTiO3 exhibited a low value of temperature coefficient of capacitance (<±8 %) in the working temperature range (up to +100 °C), room temperature dielectric constant equal to 295 and low loss tangent (0.039) which meets the specifications for “Z5F” of Class I dielectrics of Electronic Industries Association. Hence, this composition might be a suitable candidate for capacitor applications. Ac conductivity and electric modulus studies supported the hopping type of conduction in the system and frequency dependent ac conductivity data obeyed Jonscher’s power law.

K. AmarNath

Papers

Electrical properties of BaY0.5Nb0.5O3 ceramic: Impedance spectroscopy analysis

Dielectric relaxation in Ba(Y 1/2 Nb 1/2 )O 3 -BaTiO 3 ceramics