AC conductivity and dielectric studies in V2O5–TeO2 and V2O5–CoO–TeO2 glasses

Gamma radiation-induced synthesis of novel PVA/Ag/CaTiO3 nanocomposite film for flexible optoelectronics

A flexible nanocomposite film based on polyvinyl alcohol (PVA), silver nanoparticles, and calcium titanate (CaTiO₃) was synthesized using gamma radiation induced-reduction. Temperature-dependent structural, optical, DC electrical conductivity, electric modulus, and dielectric properties of PVA/Ag/CaTiO₃ nanocomposite film were investigated. The XRD pattern proved the successful preparation of the nanocomposite film. Also, as the temperature increases, the average crystallite sizes of CaTiO₃ and Ag nanoparticles decrease from 19.8 to 9.7 nm and 25 to 14.8 nm, respectively. Further, the optical band gap increased from 5.75 to 5.84 eV with increasing temperature. The thermal stability is improved, and the semiconductor behavior for PVA/Ag/CaTiO₃ nanocomposite film is confirmed by thermal activation energy ΔE with values in the 0.11-0.8 eV range. Furthermore, the maximum barrier W_m value was found of 0.29 eV. PVA/Ag/CaTiO₃ nanocomposite film exhibits a semicircular arc originating from the material's grain boundary contributions for all temperatures. The optical, DC electrical conductivity, and dielectric properties of the PVA/Ag/CaTiO₃ nanocomposite film can be suitable for flexible electronic devices such as electronic chips, optoelectronics, and energy storage applications.

Mixed Ionic and Electronic Conduction in TeO2-ZnO-V2O5 Glasses towards Good Dielectric Features

The melt-quenching technique was used to synthesize tellurite glasses of the chemical composition 80TeO₂-(20-x) ZnO-xV₂O₅. X-ray diffraction (XRD) patterns indicate the amorphous nature of the prepared glasses. Raman and FTIR measurements demonstrate a progressive substitution of the Te-O-Te linkages by the Te-O-V bridges and the formation of VO₄ and VO₅ units by a change of the vanadium coordination due to the higher number of oxygens incorporated by further addition of V₂O₅. The AC conductivity was investigated in the frequency range of 40 Hz to 10⁷ Hz between 473 K to 573 K. A good coherence of the AC conductivity was found using a model correlating the barrier hopping (CPH) and the dominant conduction process changes from ionic to polaronic with the addition of V₂O₅. The dielectric constant exhibits high values in the range of lower and medium frequencies. Both variations of the electric modulus and the dielectric loss parameters with frequency and temperature showed a relaxation character mainly assigned to the vanadate phases. The electric modulus displays a non-Debye dielectric dispersion and a relaxation process. The present results open the door to future zinc-tellurite glasses-doped vanadium exploitation as a potential electrolyte-based material for solid-state batteries.

Thermal, dielectric characteristics and conduction mechanism of azodyes derived from quinoline and their copper complexes

A novel series of (5-(4'-derivatives phenyl azo)-8-hydroxy-7-quinolinecarboxaldehyde) (AQLn) (n=1, p-OCH3; n=2, R=H; and n=3; p-NO2) and their complexes [Cu(AQLn)2]·5H2O are synthesized and investigated. The optimized bond lengths, bond angles and the calculated quantum chemical parameters for AQLn are investigated. HOMO-LUMO energy gap, absolute electronegativities, chemical potentials, and absolute hardness are also calculated. The thermal properties, dielectric properties, alternating current conductivity (σac) and conduction mechanism are investigated in the frequency range 0.1-100kHz and temperature range 293-568K for AQL1-3 and 318-693K for [Cu(AQL1-3)2]·5H2O complexes. The thermal properties are of ligands (AQLn) and their Cu(II) complexes investigated by thermogravimetric analysis (TGA). The temperature and frequency dependence of the real and the imaginary part of the dielectric constant are studied. The values of the thermal activation energy of conduction mechanism for AQLn and their complexes [Cu(AQLn)2]·5H2O under investigation are calculated at different test frequencies. The values of thermal activation energies ΔE1 and ΔE2 for AQLn and [Cu(AQLn)2]·5H2O decrease with increasing the values of frequency. The ac conductivity is found to be depending on the chemical structure of the compounds. Different conduction mechanisms have been proposed to explain the obtained experimental data. The small polaron tunneling (SPT) is the dominant conduction mechanism for AQL1 and its complex [Cu(AQL1)2]·5H2O. The quantum mechanical tunneling (QMT) is the dominant conduction mechanism for AQL2 and its complex [Cu(AQL2)2]·5H2O. The correlated barrier hopping (CBH) is the dominant conduction mechanism for AQL3 and its complex [Cu(AQL3)2]·5H2O, and the values of the maximum barrier height (Wm) are calculated.

Structural investigations on PbO-Sb(2)O(3)-B(2)O(3):CoO glass ceramics by means of spectroscopic and dielectric studies

PbO-Sb(2)O(3)-B(2)O(3) glasses mixed with different concentrations of CoO (ranging from 0 to 2.0 mol%) were crystallized. The samples were characterized by x-ray diffraction, scanning electron microscopy and differential scanning calorimetric techniques. The x-ray diffraction and scanning electron microscopic studies have revealed the presence of CoSb(2)O(6), Co(2.33)Sb(0.67)O(4), Pb(5)Sb(2)O(8),Pb(3)(SbO(4))(2), PbB(4)O(7) and Co(3)O(4) crystalline phases in these samples. The DSC studies have indicated the spreading of the crystallization from the inside to the surface of the samples as the concentration of the crystallizing agent is increased. The IR and Raman spectroscopic studies have pointed out the existence of conventional BO(3), BO(4), SbO(4) and also Co(III)-O structural units in the glass ceramic samples. These studies have further indicated the decreasing concentration of symmetrical structural vibrational groups with increase in the concentration of CoO. The results of various studies, namely dielectric properties over a range of frequency and temperature, photo-induced birefringence, optical absorption, fluorescence and magnetic susceptibility at room temperature of PbO-Sb(2)O(3)-B(2)O(3):CoO glass ceramics, have also been reported. The variations observed as a function of the concentration of crystallizing agent in all these properties have been analyzed in the light of different oxidation states and environments of cobalt ions in the glass ceramic network.