High-Temperature Dielectric Relaxation and Electric Conduction Mechanisms in a LaCoO3-Modified Na0.5Bi0.5TiO3 System

This research study examines the high-temperature dielectric relaxation and electric conduction mechanisms in (x)LaCoO₃-(1 - x)Na_0.5Bi_0.5TiO₃ samples, where x is 0.05, 0.10, and 0.15. The findings demonstrate that all the samples exhibit two dielectric transitions: first, a frequency-dispersive shoulder at a lower temperature (T_s) around 425-450 K, which is associated with polar nanoregions (PNRs), and second, from ferroelectric to paraelectric transition at the Curie temperature (T_c) approximately between 580 and 650 K. The impedance analysis reveals the negative temperature coefficient of resistance behavior of the specimens. The broad and asymmetric relaxation peaks obtained from modulus spectroscopy demonstrate a wide range of relaxations, suggesting non-Debye-type behavior. Furthermore, the conductivity studies provide insights into understanding the transport phenomena in the samples. The oxygen vacancies resulting from the addition of LaCoO₃ into the Na_0.5Bi_0.5TiO₃ ceramics are responsible for the relaxation and conduction processes, and the charge carrier is doubly ionized oxygen ion vacancies. All samples except for LCNBT10 at 1 kHz exhibit a negative magnetodielectric response.

Synthesis and characterization of nanostructured graphene-doped selenium

In this work, we explore various properties of elemental selenium glass (g-Se) by doping with graphene through the facile melt-quench technique. The structural information of the synthesized sample was found by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and Raman spectroscopy. The analyses confirm that the graphene-doped g-Se behaves like a glass-ceramic material. Electrical and dielectric measurements were performed to discover the consequences of graphene incorporation on the nano-structure of g-Se. The electrical measurements of the dielectric parameters (i.e., dielectric constant ε' and loss ε'') and conductivity (σ _ac) reveal that graphene incorporation causes a rise in the dielectric constant but simultaneously increases dielectric loss. The enhancement in ε' and ε'' values is thought to be a consequence of the interface effect between graphene and the host selenium glass. Calorimetric experiments were performed in a standard differential scanning calorimetry (DSC) unit on the glassy nanocomposite in non-isothermal mode. By measuring the kinetic temperatures at four heating rates, the kinetics of the crystallization/glass transition were studied. The results were examined to understand the role of graphene doping on the well-known phase transitions (i.e., glass transition and crystallization) of g-Se.

Comprehensive studies of temperature and frequency dependent dielectric and a.c. conducting parameters in third generation multi-component glasses

The dielectric relaxation and thermally assisted a.c. conduction play an important role in understanding the conduction mechanism in chalcogenide glasses. These two phenomena are often the deciding factors of the suitability of chalcogenide materials for particular device applications. Dielectric relaxation studies are important to understand the nature and origin of dielectric losses, which, in effect, may be useful in the determination of structure and defects in solids. The study of thermally assisted a.c. conduction can be used as a tool to understand the nature of defect states and the estimation of their density of defect states. In this paper, therefore, we have studied the metal-induced effects of cadmium (Cd), indium (In) and antimony (Sb) on dielectric relaxation and thermally activated a.c. conduction in ternary Se₈₀Te₁₈Sn₂ glass. The density of charged defect states in quaternary Se₈₀Te₈Sn₂M₁₀ alloys is found to vary with the electro-negativity difference (ξ _M - ξ _Te) of the foreign element M and Te. Further analysis shows that the increasing sequence of the density of charged defects is explained in terms of variation in the lone-pair electrons after the incorporation of Cd, In and Sb.

Hybrid materials based on transition metal–BTC–benzimidazole: solvent assisted crystallographic and structural switching

Five transition metal–BTC–BIm based coordination polymers with hierarchical structures were synthesized under hydro/solvothermal condition. Crystal structure analysis of the compounds showed that 1 forms a 1D chain, 2 and 3 have 2D layers, while 4 and 5 have three-dimensional architectures.