Prasun Ganguly

Bio: Prasun Ganguly is an academic researcher from Delhi Technological University. The author has contributed to research in topics: Dielectric & Ferroelectricity. The author has an hindex of 11, co-authored 16 publications receiving 302 citations.

Dielectric and Pyroelectric Studies of Tungsten—Bronze Structured Ba5SmTi3Nb7O30 Ferroelectric Ceramics

Abstract: In the present work, sample of composition Ba 5 SmTi 3 Nb 7 O 30 was prepared by solid-state reaction method. X-ray diffraction (XRD) analysis reveals the formation of single-phase compound with an orthorhombic structure. The grain morphology of the sample has been investigated by scanning electron microscopy. Dielectric properties of the compound have been studied as a function of temperature and frequency. The variation of dielectric constant (ϵ′r) with temperature at different frequencies shows that the compound has a dielectric anomaly of ferroelectric to paraelectric type at 170°C, and exhibits non-relaxor kind of diffuse phase transition. At different frequencies, the variation of dielectric loss (tan δ) with temperature shows at lower temperatures the loss is almost constant and increases sharply at higher temperatures. The frequency dependence of dielectric constant and loss show a decreasing trend upto 10 kHz and beyond this frequency they remain almost constant. The variation of pyroelectric coe...

Impedance spectroscopy analysis of Ba5NdTi3Nb7O30 ferroelectric ceramic

Abstract: The polycrystalline sample of Ba5NdTi3Nb7O30, a member of tungsten bronze family, was prepared by solid-state reaction method. X-ray diffraction (XRD) analysis shows the formation of single-phase compound with an orthorhombic structure. Scanning electron micrograph of the material shows uniform grain distribution throughout the sample. Variation of dielectric constant (e′r) with temperature at different frequencies shows that the compound has a dielectric anomaly of ferroelectric to paraelectric type at 100 °C, and exhibits non-relaxor kind of diffuse phase transition. Studies of electrical properties of Ba5NdTi3Nb7O30 using the complex impedance spectroscopy (CIS) technique show the decrease in bulk resistance with rise in temperature indicating a typical negative temperature coefficient of resistance (NTCR)-type behaviour. A possible hopping mechanism for electrical transport in the system is evident from the modulus analysis.

Investigation of conduction and relaxation phenomena in LaFe 0.9 Ni 0.1 O 3 by impedance spectroscopy

Abstract: Polycrystalline LaFe0.9Ni0.1O3 is prepared by the solid state reactions route. X-ray diffraction is used to analyse the phase purity of the compound. Impedance spectra of LaFe0.9Ni0.1O3 over the frequency range of 1?Hz to 10?MHz are investigated at different temperatures from 100 to 373?K. Two relaxation processes with different relaxation times are observed at each temperature. An equivalent circuit model (R1Q1) (R2Q2) is applied to explore the physical parameters associated with grains and grain boundaries. Frequency and temperature dependence of the relaxation processes and extracted parameters are discussed in terms of hopping between Fe+4 and Fe+3 and trap state scattering at grain boundaries. A change in conduction mechanism from variable range hopping to adiabatic small polaron hopping at 296?K is evident from these results. Traps are active below 296?K in capturing the charge.

Small polaronic hole hopping mechanism and Maxwell-Wagner relaxation in NdFeO3

Abstract: In the modern micro-electronics, transition metal oxides due to their colossal values of dielectric permittivity possess huge potential for the development of capacitive energy storage devices. In the present work, the dielectric permittivity and the effects of temperature and frequency on the electrical transport properties of polycrystalline NdFeO3, prepared by solid state reaction method, are discussed. Room temperature Mossbauer spectrum confirms the phase purity, octahedral environment for Fe ion, and high spin state of Fe3+ ion. From the impedance spectroscopic measurements, three relaxation processes are observed, which are related to grains, grain boundaries (gbs), and electrode-semiconductor contact in the measured temperature and frequency ranges. Decrease in resistances and relaxation times of the grains and grain boundaries with temperature confirms the involvement of thermally activated conduction mechanisms. Same type of charge carriers (i.e., small polaron hole hopping) have been found resp...

Ferroelectric Transition and Low-Temperature Dielectric Relaxations in Filled Tungsten Bronzes

Abstract: A comprehensive review on the latest development of the ferroelectric transition and low-temperature dielectric relaxations of filled tungsten bronze ceramics are presented together with some new issues. In the filled tungsten bronze ceramics M6−pRpTi2+pNb8−pO30 (p = 1, 2; M = Ba or Sr; R = rare earth or Bi), a ferroelectric transition is generally indicated together with up to three low-temperature dielectric relaxations. The ferroelectric transition is determined as 4/mmm → 4 mm, and the low-temperature dielectric relaxations are deeply concerned with the structure modulations due to the order/disorder of ions in A1 and A2 sites, their random cross occupancy, and the order/disorder of B-site ions. Both the ferroelectric transition and low-temperature dielectric relaxations are dominated by the composition and radius difference between A1- and A2-site ions, ∆r. The normal ferroelectric transition might be expected if the ratio of the biggest ion and second big ion is 2:1, otherwise the diffuse or relaxor ferroelectric is expected. Meanwhile, the larger ∆r generally results in the normal ferroelectric, and the smaller ∆r will lead to the diffuse or relaxor ferroelectric. Moreover, the effects of A sites order/disorder and the random cross occupancy of A-site ions are primary, and the effects of B-site ordering/disordering are secondary. The right ratio of 2:1 for A2- and A1-site ions and the large ∆r should be the guidelines for designing the possible multiferroic tungsten bronzes.