The modulus and impedance spectroscopy studies on barium strontium lanthanum bismuth niobate (Ba 0.1 Sr 0.81 La 0.06 Bi 2 Nb 2 O 9 , BSLBN) were investigated in the frequency range, 45 Hz–5 MHz and in the temperature duration from room temperature (rt) to 570 °C. The dielectric anomaly with a broad peak was observed at 485 °C. Simultaneous substitution of Ba 2+ and La 3+ increases the transition temperature of SrBi 2 Nb 2 O 9 (SBN) from 392 to 485 °C. XRD studies in BSLBN revealed an orthorhombic structure with lattice parameters a  = 5.5023 Ǻ, b / a  = 1.000 and c  = 25.0697 Ǻ. Impedance and modulus plots were used as tools to analyze the sample behavior as a function of frequency. Cole–Cole plots showed non-Debye relaxation. DC and AC conductivity measurements were performed on BSLBN. The electric modulus which describes the dielectric relaxation behavior is fitted to the Kohlrausch exponential function. Near the phase transition temperature, a stretched exponential parameter β indicating the degree of distribution of the relaxation time has a small value.

Impedance and modulus spectroscopy studies on Ba0.1Sr0.81La0.06Bi2Nb2O9 ceramic

Electrical conductivity effects in biaxially stretched polyethylene terephthalate (PET) films of 6 μm thickness and 68% degree of crystallinity were investigated by means of dielectric relaxation spectroscopy in the frequency range 10−2–106 Hz and at temperatures higher than the glass transition temperature (∼85 °C) up to 190 °C. The formalisms of complex permittivity, electric modulus, and impedance were employed to analyze the experimental data. The results are discussed in terms of dc conductivity, conductivity current relaxation, interfacial Maxwell–Wagner–Sillars polarization, ρ peak, space-charge polarization, and electrode polarization. They are compared with the predictions of models for the electrical and dielectric properties of ion-conducting polymers. The dc conductivity values determined from dc measurement, from ac conductivity plots and from complex impedance plots agree well with each other. Their temperature dependence is described by the Vogel–Tammann–Fulcher equation and classifies PET ...

Electrical conductivity effects in polyethylene terephthalate films

Superprotonic conduction and ferroelectricity in addition cesium sulfate tellurate Cs2SO4.Te(OH)6

Barium Strontium Bismuth Niobate Layered Perovskites: Dielectric, Impedance and Electrical Modulus Characteristics M.P. Dasaria,∗, K. Sambasiva Rao, P. Murali Krishna and G. Gopala Krishna Department of Physics, Gitam Institute of Technology, Gitam University Visakhapatnam-530 045, India Centre for Piezoelectric Transducer Materials, Physics Department, Andhra University Visakhapatnam-530 003, India

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Barium Strontium Bismuth Niobate Layered Perovskites: Dielectric, Impedance and Electrical Modulus Characteristics

In order to examine the influence of phosphate impurities upon the conduction properties of SnP2O7, SnP2O7-H3PO4 composites were synthesised through different methods with varying starting P:Sn molar ratios. The composites were then carefully characterised by XRD, SEM, HRTEM, NMR, FT-IR and a.c. impedance spectroscopy to explore the phase compositions and electrical properties. It was found that cubic SnP2O7 is the main crystalline phase and amorphous phases were observed when starting P:Sn ratios exceeded 2 : 1. Solid State 31P NMR confirmed residual phosphoric acid in samples with high starting P:Sn ratios whilst impedance spectroscopy indicated these to be good proton conductors. The highest conductivity observed was 3.5 × 10−2 S/cm at 300 °C in air for samples with high starting P:Sn ratios and calcined at higher temperatures. The conductivity stability of the composites was found to be promising, suggesting a new approach for the development of technically useful proton conductors.

Intermediate temperature stable proton conductors based upon SnP2O7, including additional H3PO4

Conductivity relaxation parameters of some H+ and K+ conducting in the polycrystalline compound KDyHP3O10

Low-frequency dielectric dispersion phenomena in NH 4 DyHP 3 O 10 (ammonium dysprosium hydrogen phosphate type) polycrystalline compounds have been analyzed by impedance spectroscopy. The thermal evolution of the dielectric constant shows a phase transition at 305 K which is ferroelectric-paraelectric type. The ferroelectric phase is isotypic with KDyHP 3 O 10 and exhibits the triclinic symmetry P1 (at room temperature: a = 6.820 A, b = 7.583 A, c = 8.467 A, a = 104.396°, β = 103.545°, y = 90.349°, Z = 2). An empirical expression has been deduced for the complex permittivity e * (ω), e * (ω) = e∞ + e s -e∞/ 1 + (iω/ω 1 ) + σ 0 /e 0 ω [1 + (iω/ω 2 ) n ], where the (ω 1 , m) and (ω 2 , n) couples characterize the lattice and the charge carriers responses, respectively. This relation may be considered as a generalisation of the Cole-Cole dielectric expression. The influence of the charge carrier contribution on the dielectric permittivity at low frequency is significant, as shown when both lattice and carrier polarization mechanisms are simultaneously considered.

Structural and Electrical Properties of the NH4DyHP3O10 Compound

Single crystals and polycrystalline samples of KH(SO 4 ) 0.8 (SeO 4 ) 0.2 were obtained by slow evaporation at 300 K. The samples were characterized by X-ray diffraction, examined by Raman vibrational spectroscopy and impedance spectroscopy technique. At high temperatures, no phase transition leading to a superionic phase was found. KH(SO 4 ) 0.8 (SeO 4 ) 0.2 is characterized by a medium conductivity σ 3 x 10 -8 Ω -1 cm -1 and an activation energy E a m 0.5 eV.

Conductivity and Structural Studies of New Mixed Potassium Hydrogeno‐Sulphate Selenate KH(SO4)0.8(SeO4)0.2

The phase transition in the mixed Cs 0.9 (NH 4 ) 0.1 HSO 4 were characterized by differential scanning calorimetry and Raman spectroscopy studies at temperatures ranging from 300 to 500 K. The I-II transition is characterized by the conversion of infinite (HSOj) n chains into cyclic (HSO 4 - ) 2 dimers. The II-III phase transition corresponds to a superprotonic phase transition (STP) where protons and SO 2- 4 ions contribute to the unusually high conductivity. The activation energy was determined from the plot of Δυ 1/2 as a function of temperature for the υ S-OH bands and from the conductivities. The two values have the same order of magnitude.

M. Mnif

Papers

Conductivity relaxation parameters of some H+ and K+ conducting in the polycrystalline compound KDyHP3O10

Structural and Electrical Properties of the NH4DyHP3O10 Compound

Conductivity and Structural Studies of New Mixed Potassium Hydrogeno‐Sulphate Selenate KH(SO4)0.8(SeO4)0.2

Phase Transition and Raman Studies on Cs0.9(NH4)0.1HSO4