Study of Structural and Electrical Properties of a New Type of Complex Tungsten Bronze Electroceramics; Li<sub>2</sub>Pb<sub>2</sub>Y<sub>2</sub>W<sub>2</sub>Ti<sub>4</sub>V<sub>4</sub>O<sub>30</sub>

Abstract

A polycrystalline ceramic, a new type of complex tungsten bronze type structure, having a general formula Li 2 Pb 2 Y 2 W 2 Ti 4 V 4 O 30 has been prepared relatively at low temperature using a mixed-oxide technique after optimizing the calcination conditions on the basis of thermal analysis. The material has been characterized by different experimental techniques. The formation of the material under the reported conditions has been confirmed by an X-ray diffraction technique. A preliminary structural analysis of the material showed the formation of single phase compound in an orthorhombic crystal structure at room temperature. Studies of dielectric properties (ε r , tanδ ) of the above compound as a function of temperature at different frequencies exhibit 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 microstructure. The temperature dependence of electrical relaxation phenomenon in the material 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.

Hydrothermally Synthesized h-MoO3 and α-MoO3 Nanocrystals: New Findings on Crystal-Structure-Dependent Charge Transport

“…It is noted that the value of E aσ matches well with the value of E aτ for h-MoO 3 and α-MoO 3 . The close resemblance of the activation energies indicates that the same type of charge carriers may be involved in both the conduction and relaxation processes. − …”

Mn‐Doped Ba0.45Sr0.55TiO3 Ceramic Systems: Dielectric and Impedance Spectroscopic Characterization

“…Low magnitude of tan δ was recorded for the samples with x = 0.04 around room temperature as 0.007 at 100 kHz. Factors such as crystal defects, formation of space charge, and distortion in the crystal lattice are responsible for the tan δ in materials . The small amount of Mn results in the reduction of Ti 4+ to Ti 3+ by neutralizing the donor action of oxygen vacancies (2Ti 4+ → 2Ti 3+ + ).…”

Reduced impedance in dual substituted strontium cobaltite nanoparticles for renewable energy applications

“…As the grain boundaries resistance was reduced, the opposition provided by the electrons to hop decreased. Consequently, impedance of hydrothermally synthesized samples decreased at higher temperatures [41,50,51]. The dominant conduction mechanism in this case was conduction along the and through the grain boundaries [40].…”

“…After 792°C, an endothermic peak was appeared at 919°C in the DTA curve. Along with this endothermic change, TGA curve followed a steady weight loss which was assigned to the decomposition of carbonate (BaCO 3 , SrCO 3 ) impurities and development of barium strontium iron cobaltite (Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3−δ ) [28,29,34,38,41] product. Afterwards, with continues heating up to 1200°C, led to a slight increase in weight was appeared which was credited to the rise of oxygen content (δ) per formula unit cell in Ba 0.5 Sr 0.5 Co 0.8 Fe 0.…”

“…With the successive increase of temperature, electrons gained adequate thermal energy required for hopping. The decrease of impedance and increase of conductivity against temperature was due to increase of the rate of successful hopping [27,33,41]. Moreover, decrease of impedance can be caused by the increase of vacant sites with the increase of temperature (100 to 600°C).…”