Structural and Electrical Properties of Complex Tungsten Bronze Ferroelectrics ; Li₂Pb₂La₂W₂Ti₄V₄O₃₀

Abstract

The polycrystalline sample of a new tungsten bronze ferroelectric vanadate, Li 2 Pb 2 La 2 W 2 Ti 4 V 4 O 30 , was prepared at a relatively low temperature using a mixedoxide technique. The formation of the material under the reported conditions has been confirmed by an X-ray diffraction technique. A preliminary structural analysis exhibits orthorhombic crystal structure of the material at room temperature. Studies of dielectric properties (ε, tanδ) of the above compound as a function of temperature (273-600K) at frequencies 10, 100, 1000 KHz exhibits a ferroelectric phase transition of diffuse type. The electrical properties of the material have been studied using ac impedance spectroscopy technique. Detailed studies of impedance and related parameters exhibit that the electrical properties of the material are strongly dependent on temperature, and bear a good correlation with its microstructures. The temperature dependence of electrical relaxation phenomenon in the materials has been observed. The bulk resistance, evaluated from complex impedance spectra, is found to decrease with rise in temperature, exhibiting a typical negative temperature co-efficient of resistance (NTCR) -type behavior similar to that of semiconductors. A small contribution of grain boundary effect was also observed. The complex electric modulus analysis indicates the possibility of hopping conduction mechanism in the system with non-exponential type of conductivity relaxation. The ac conductivity spectra exhibit a typical signature of an ionic conducting system, and are found to obey Jonscher's universal power law.

Synthesis, structural and dielectric properties of Ho-doped SrBi2Nb2O9 prepared by Co-precipitation method

“…The value of εʹ shows a sharp decrease with increasing frequencies. The strong decrease of dielectric constant towards a high frequency range may be due to the space charge polarization and interface effect [16]. However, this parameter tends to be constant for the Ho-doped SBN.…”

Study of multiferroic properties of Bi2Fe2WO9 ceramic for device application

“…The presence of two semicircular arcs indicates the existence of two different relaxation processes and distribution of relaxation time instead of a single relaxation time. In ideal Debye-type relaxation, a semicircle with its center at Z 0 -axis should be observed, 29 but depressed semi-circles of non-Debye type of relaxation are observed. The nature of plots suggest that the overall electrical processes in the compound arise mainly due to the contribution from grain and grain boundary, 29 and thus can be modeled as an equivalent electrical circuit.…”

“…In ideal Debye-type relaxation, a semicircle with its center at Z 0 -axis should be observed, 29 but depressed semi-circles of non-Debye type of relaxation are observed. The nature of plots suggest that the overall electrical processes in the compound arise mainly due to the contribution from grain and grain boundary, 29 and thus can be modeled as an equivalent electrical circuit. This figure compares the impedance data with fitted data using commercially available software ZSIMP WIN version 2.…”

Structural and Electrical Properties of Barium Strontium Cobaltite Nanoparticles Synthesized by Wet Chemical Methods

“…With the sufficient thermal energy provided, electrons cross the barrier and take part in hopping. With the increase in temperature, rate of successful hopping increases that in turns increases the conductivity [4,13]. The increase in temperature increases the vacancy sites which are also responsible for increase of conductivity following jump relaxation model [14].…”

“…At higher temperature, sufficient thermal energy was available for the electrons to hop. With increase in rate of successful hopping, conductivity increases and hence impedances decrease [2,13].…”