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In this study, Vanadium pentoxide (VO) -graphene composite (VRGO) is prepared by simple hydrothermal treatment. VO nanoparticles are prepared by solvothermal method using environmentally benign precursor, vanadium oxide acetyl acetonate. Graphene oxide (GO) prepared by modified Hummer's method is the origin for graphene in prepared composite. GO is wrapped onto VO nanoparticles then subsequently reduced to graphene using simple heat treatment, thus avoiding the use of harmful reducing agents. This composite is characterized by X-ray diffraction for the structural analysis, scanning electron microscopy to identify the morphology, confocal Raman microscopy and Fourier transform infra-red spectroscopy for molecular structure and chemical bonds present in the composite. The BET surface area analyzer is used for surface area analysis and impedance analyzer for electrical studies. Impedance analysis carried out at room temperature shows a considerable decrease in the resistance of prepared composite VRGO, in comparison to bare VO thus providing a good conductivity for the sample. [ABSTRACT FROM AUTHOR]

Abstract: An attempt has been made to synthesize nanocrystalline high dense lithium ferrite, namely, Li0.5M x Fe2.5−x O4 (M = Bi, Pb; x = 0, 0.02) by a solution combustion technique. Various characterization methods like XRD and TG-DTA were employed to validate the structure and phase purity. UV–vis diffuse reflectance spectroscopic studies were conducted to obtain the oxidation states of metal ions. Raman analysis was used to identify the phonon modes involved in specific atomic motions present in the synthesized materials. Morphology of sample surface was explored by electron microscope and elemental analysis was done by energy dispersive analysis. The nanocrystalline nature of the materials were confirmed through transmission electron microscopy. Strong temperature dependence of electron spin resonance linewidth was exhibited by the samples and a resonance field was observed for all the materials. Ac electrical properties were investigated using the super-linear power law and activation energies were calculated for all compositions. The conductivity data were consistent with an asymmetric double well potential model. [Copyright &y& Elsevier]

Abstract: Nanocrystalline Li2Ni1−x Mg x TiO4 powders were synthesized using a sol–gel technique. They were crystallized in cubic rock salt phase with space group Fm-3m. The synthesis was carried out in nitrogen atmosphere using citric acid as fuel. AC electrical properties of the nanocrystalline Li2Ni1−x Mg x TiO4 were investigated by complex conductivity and impedance. The scaling behavior in the electrical conductivity and impedance confirmed the time temperature superposition principle of relaxation mechanism. [Copyright &y& Elsevier]

Abstract: Nano-crystallites of Li1.3Ti1.7Al0.3(PO4)2.9(VO4)0.1 NASICON type material are prepared by means of solid-state reaction of a stoichiometric mixture after milling it for 22 and 55h. The milling reduces the average crystallite size of the ceramic to 80 and 60nm, respectively. Mechanical milling changes structural parameters and the strain induced at the grain-boundaries plays a major role in improving electrical conductivity. An order of magnitude increase in electrical conductivity is observed in the material milled for 55h compared to the unmilled material, which is also reflected in permittivity loss. Modulus and permittivity representations substantiate the constriction effect of grain-boundaries observed in the complex impedance representation. [Copyright &y& Elsevier]

Abstract: Ion transport properties of Na2NbZnP3O12, Na2NbCdP3O12, Na2NbPbP3O12, Na2NbCuP3O12 and Li2NbPbP3O12 phosphate glasses were investigated over a frequency range from 100Hz to 1MHz at different temperatures. The non-Debye behaviors in real part of ac conductivity and permittivity of these glasses were analyzed using Jonscher''s universal power law (UPL), and anomalous diffusion model (ADM). The ADM was used to extract the dc conductivity and the relevant physical parameters, namely, crossover length and relaxation frequency in the ion diffusion process. The dc conductivity extracted from UPL matches well with ADM and hence their activation energy. The electric modulus data were analyzed using the Kohlrausch–Williams–Watts (KWW) stretched exponential function and ADM. The ADM fits superior to the KWW in the high frequency wing of electric modulus. [Copyright &y& Elsevier]

Abstract: Niobium based glasses of composition Na2NbMP3O12 (where M=Cd, Zn, Pb and Cu) have been synthesized by melt quenching method and characterized by XRD, FTIR and DSC. The ac conductivity measurements have been carried out over wide range of frequencies at different temperatures on these glassy systems. Ac conductivity data are analyzed using conductivity and electric modulus formalisms. The bulk dc conductivity obtained from complex impedance plots follow the Arrhenius behavior and its activation energy matches well with the activation energy obtained from electric modulus formalism. The ac conductivity plot exhibits universal power law features and the temperature dependence of dc and ac conductivity is discussed. The scaling behavior of the ac conductivity and electric modulus spectra with respect to temperature are discussed and reported for these glassy systems. [Copyright &y& Elsevier]

Abstract: The ac electrical conductivity properties of LiTi2(PO4)3 (LTP) polycrystalline material in two different crystallite sizes are compared. Micrometer sized LTP is prepared by conventional solid-state reaction. LTP crystallites of 71nm size are prepared by solid-state reaction of 40h planetary milled stoichiometric mixture. The XRD and SEM are used as characterization techniques. Electrical properties are studied using impedance spectroscopic technique. Ball-milled LTP shows one order increase in grain-interior conduction compared to microcrystalline LTP at 388K. The increase in conduction results from decreased crystallite size. [Copyright &y& Elsevier]

Abstract: Vitreous M4AlCdP3O12 (M=Li, Na, K) NASICON-type materials are synthesized, characterized and their electrical properties are reported at different temperatures in the frequency range of 42Hz to 1MHz. Ac conductivity and permittivity data are analyzed by using conductivity formalism. The dc conductivity and hopping frequency are thermally activated and their activation energies found to be in the range of 0.79–0.85eV. The variation of dielectric permittivity with frequency is attributed to ion diffusion and polarization occurring in the NASICON-type vitreous materials. Scaling in conductivity and permittivity shows that the relaxation mechanisms are independent of temperature for the NASICON-type vitreous materials. [Copyright &y& Elsevier]

Abstract: Conductivity dispersion, electric modulus and their scaling are studied for Na3M2P3O12 orthophosphate (M2=Fe2, TiCd, TiZn) glassy and crystallized glassy materials in the frequency range 20Hz to 1MHz at different temperatures (T). The power law and the stretched exponential approaches are used to analyze dispersion data. The DC conductivity σDC of crystallized glass is found to be greater than that of the parent glass. The conductivity scaling is studied with different scaling parameters like hopping frequency , the Summerfield scaling parameter σDCT and modified the Summerfield scaling parameter , where shows the temperature dependence. Ngai''s correlation is also observed between power-law exponent n and stretched exponent . [Copyright &y& Elsevier]

Ac conductivity measurements and its scaling analysis is studied on the new sodium and lithium bismuthate systems xNa2O+(1−x)Bi2O3 and xLi2O+(1−x)Bi2O3 for various compositions in the frequency range from 20 Hz to 1 MHz and in the temperature range from 467 to 750 K. The measured electrical relaxation data of these glasses are analysed using Jonscher''s universal power law (UPL) and random free energy barrier model (RFEBM). All experimentally known features of the ac conductivity, including its scaling behavior, are explained satisfactorily based on the power law and random free energy barrier model. [Copyright &y& Elsevier]

A.c. conductivity measurements and its analysis are performed on the xNa2O + (1 - x)B2O3 ionic conducting glass system, where 0.05 < x < 0.45. The a.c. conductivity data are analysed using both Jonscher's power law and diffusion controlled relaxation (DCR) model. The DCR model is used to interpret the observed dispersion in a.c. conductivity in terms of diffusion controlled dielectric loss relaxation mechanism. All the known experimental features of the σ(ω) including scaling behavior are explained satisfactorily. The results show an excellent agreement with scaling behavior based on loss peak frequency. [ABSTRACT FROM AUTHOR]

Ac conductivity measurements and its analysis has been performed on the glassy ionic conducting x Na2O + (1 − x) Bi2O3 system in the frequency range from 20 Hz to 1 MHz and in the temperature range 450 K to 750 K. The composition dependence of the dc electrical conductivity and activation energy has been obtained. The electrical relaxation analysis has been inquired on these glasses with universal power law and the random free energy barrier model. The relaxation parameters are obtained from the analysis has been compared. All experimentally known features of the σ′(ω) including its scaling behavior are explained satisfactorily. The results show an excellent agreement of scaling behavior based on random free energy barrier model and universal power law. [ABSTRACT FROM AUTHOR]

Different NASICON type ionic conducting systems with general formula AmBnP3O12 were prepared by quenching method, where A=Na, and B=Al, Ti, AlCd, TiCd and TiZn. The prepared compounds were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). The electrical conductivity measurements were made on the different systems as a function of frequency at different temperatures. Jonscher''s universal power law is applied to discuss the ac and dc conductivity and the scaling of conductivity spectrum. The conductivity spectra of the compounds show the power law feature and scaling behavior when the conductivity spectra are scaled vertically by dc conductivity and horizontally by hopping rate. The dc conductivity of the compounds is found to be in the range 10−9–10−6 S cm−1 at 423 K. The dc conductivity and hopping rate activation energies are found to be in the range 0.47–1.13 eV. [Copyright &y& Elsevier]

Most of the crystalline materials seldom show a well-defined dielectric loss peak due to domination of dc conductivity contribution, but effects of loss peaks are seen at high frequencies. Ac electrical data of nano-crystalline Mn 0.5 Zn 0.5 Fe 2 O 4 synthesised by chemical co-precipitation method show such behaviour. Properly combined and formulated conduction and dielectric relaxation functions are required for such materials. Cole–Cole type relaxation function in the combined conduction and dielectric process is formulated for complex resistivity ρ ⁎ ( ω ) , complex permittivity ε ⁎ ( ω ) , complex conductivity σ ⁎ ( ω ) and complex electric modulus M ⁎ ( ω ) . Conduction and dielectric relaxation are linked to Jonscher's idea of ‘pinned dipole’ and ‘free dipole’ to understand the relaxation dynamics. The physical parameters of ‘pinned dipole’ and ‘free dipole’ formalism are unique for all representations like ρ ⁎ ( ω ) , ε ⁎ ( ω ) , σ ⁎ ( ω ) and M ⁎ ( ω ) . ‘Pinned dipole’ relaxation time τ c related to conduction process and ‘free dipole’ relaxation time τ d related to dielectric process show Arrhenius behaviour with the same activation energy. Correlation of dc conductivity σ c with τ c and τ d indicates the coupled dynamics of ‘pinned dipole’ and ‘free dipole’. Time–temperature scaling of conduction and dielectric relaxation reveals that the mechanism of coupled dynamics of ‘pinned dipole’ and ‘free dipole’ is temperature independent. Hopping of charge carriers with dynamics of disordered cation distribution of host matrix generates a coupled conduction and dielectric relaxation in Mn 0.5 Zn 0.5 Fe 2 O 4 . [ABSTRACT FROM AUTHOR]

• Mixed ionic effect in (Li (1-x) Na x) 5 TiP 3 O 12 glass through thermal parameters, GFA, GS was spoted. • Stength of mixed ion in glass transition temperatures and dc conductivity was estimated. • Mixed alkali content in glassy phase plays a vital role in ionic transport and hopping relaxation. • Different conductivity spectra and electrical modulus scaling were exposed. • Dixon scaling is better in electrical modulus scaling. A NASICON based phosphate glass systems (Li (1-x) Na x) 5 TiP 3 O 12 with various composition x = 0, 0.2, 0.4, 0.6, 0.8 and 1.0 were synthesized by melt quenching method. X-ray diffraction patterns substantiate the amorphous nature. The mixed alkali effect (MAE) was explicated in thermal studies as well as in dielectric spectroscopy. The thermal analysis demonstrates that the series exhibit a MAE in their characteristic thermal parameters also. The dynamics of the ions in mixed alkali glass illustrate miniaturization of dc conductivity and maximum in their respective activation energy at x = 0.6. This decrease in conductivity in the glass composition is observed in all temperature range 273 K to 473 K and follows the same manner as glass transition temperature. The frequency dependence ac conductivity, as well as the electric modulus espouse a few interesting aspects of scaling regarding MAE. [ABSTRACT FROM AUTHOR]

Abstract: Thermally stable Na3Cr2(PO4)3 nano-crystallites are synthesized through novel solution combustion technique using glycine fuel in three molar ratios. Effects of fuel molar ratio on structural and electrical properties are investigated. Reaction parameters like fuel molar ratio, flame temperature and number of moles of gases evolved, play a major role in deciding physical and electrical properties. Out of the synthesized samples, one which contains fuel in 1:1 molar ratio shows highest grain conductivity of 2.35×10−6 Scm−1. Improved conductivity is elucidated by least size and highest density of the crystallites, which in turn is decided by the flame temperature. Ac electrical properties are investigated using complex impedance spectroscopy. Activation energies for dc conduction and relaxation are determined and the results are reported. [Copyright &y& Elsevier]

Highlights: [•] Gd doped CeO2 was successfully synthesized by carbonate co-precipitation method. [•] Lattice parameters and unit cell volume increases with increase in Gd concentration. [•] The optical absorption spectra of GDC20 exhibits a red shift when compare to pure CeO2. [•] Total conductivity of GDC10 and GDC20 is almost same between 473K and 623K. [ABSTRACT FROM AUTHOR]

Abstract: The effect of Co-60 gamma irradiation on l-alanine cadmium chloride (LACC), l-alanine doped potassium dihydrogen orthophosphate (KDP) and l-arginine doped KDP nonlinear optical (NLO) single crystals were studied in doses ranging from 100krad to 6Mrad. The crystals were grown by slow evaporation method at room temperature. The effects of gamma irradiation on the chemical, surface morphology, DC electrical conductivity, thermal and mechanical properties of the grown crystals have been studied. The functional groups of unirradiated and irradiated crystals have been identified and confirmed by Fourier transform infrared (FTIR) studies. Scanning electron microscopy (SEM) of irradiated crystals shows some morphological changes in the crystals. The dc conductivity of LACC and l-alanine doped KDP crystals were found to increase with increase in radiation dose whereas in case of l-arginine doped KDP crystals, the dc conductivity was found to decrease with increase in radiation dose. Differential scanning calorimetry (DSC) thermograms reveals that there is no significant change in the melting point of the crystals after irradiation and the crystals does not decompose as a result of irradiation. The mechanical behavior of both unirradiated and irradiated crystals is explained with the indentation effects using Vicker’s microhardness tester. The Vicker’s hardness number HV and Mayer’s index ‘n’ has been estimated and confirms that LACC belong to the hard materials. [Copyright &y& Elsevier]

Abstract: Third generation 200GHz silicon–germanium Heterojunction Bipolar Transistors (Si–Ge HBTs) were irradiated with high dose Co-60 gamma radiation up to 100Mrad. Pre-radiation and post-radiation DC figures of merits were used to quantify the radiation tolerance of the different geometry devices. The different electrical characteristics like Gummel measurements, excess base current, current gain, transconductance, neutral base recombination, avalanche multiplication of carriers and output characteristics were studied for different doses from 100krad to 100Mrad of total doses. The Si–Ge HBTs showed robust ionizing radiation tolerance up to a total dose of 100Mrad. [ABSTRACT FROM AUTHOR]