Dielectric Properties of γ-Iirradiated, Stretched, and Poled PVDF Thin Films

The effects of γ‐irradiation on the dielectric properties of stretched and poled polyvinylidene fluoride thin films synthesized by solvent cast method are reported. The films are subjected to γ‐irradiation with different doses (25, 50, and 75 kGy). XRD pattern is obtained to identify the presence of α/β phases. Dielectric constant and loss values of the stretched and poled films have been measured, before and after irradiation, and their nature of variation has been studied. β phase is retained even after the irradiation thereby confirming that the radiation damage is not significant. The dielectric loss is minimum in the frequency range 102 to104 Hz, giving the preferable frequency range of operation for device

ac conductivity studies on the electron irradiated BaZrO3BaZrO_3 ceramic

Barium zirconate $(BaZrO_3)$ powder samples were synthesized by ceramic method and their response to the high energy electron irradiation was studied in terms of their ac conductivity, dielectric constant and dielectric losses. Samples were irradiated with the 8 MeV electrons with an absorbed dose of 100 kGy. The ac conductivity is explained by the charge carrier hopping model. Irradiated $BaZrO_3$ samples exhibited a significant variation of the frequency dependent exponent (s). The ‘s’ parameter decreased after irradiation. The activation energy calculated from the Arrhenius plots was found to increase from 0.06 eV to 0.16 eV after irradiation

Composition dependent elastic and thermal properties of Li-Zn ferrites

We report the composition dependent elastic and thermal properties of LieZn ferrite (Li(0.5-x/2)ZnxFe(2.5-x/) O-2(4), x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) ceramics. The IR absorption frequencies (obtained from the Fourier transform infrared spectra), the lattice parameters and the mass-densities were used to evaluate the elastic and thermal parameters such as force constant, elastic moduli and Debye temperature of the studied LieZn ferrite samples as a function of Zn-content x. The observed force constants were low in value for the octahedral site complexes than that of the tetrahedral site complexes, but both the force constants were increasing with increasing Zn content. The longitudinal elastic wave velocities in the sample were higher than the transverse wave velocities. The elastic moduli such as Young's modulus (E), bulk modulus (B) and rigidity modulus (G) showed increasing trends with Zn concentration in the samples. The calculated Debye temperature (theta(D)) is near to the literature values obtained experimentally. Our results provide a better understanding of the variation of mechanical, elastic and thermal properties of LieZn ferrites. (C) 2017 Elsevier B.V. All rights reserved

Combustion synthesis, structure and magnetic properties of Li-Zn ferrite ceramic powders

We report the effect of Zn-substitution on the structure and magnetic properties of Li-ferrite powders (Li0.5-x/2ZnxFe2.5-x/2O4, x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) synthesized by combustion synthesis route. Different stages involved during progress of combustion synthesis of Li-Zn ferrite samples were monitored by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The scanning electron micrographs of the synthesized samples show foamy network type of morphology with rod-shaped particles. Rietveld refinement of the X-ray diffraction (XRD) data confirmed the preferential occupancy of the Zn-atoms at the tetrahedral sites and the Li atoms at the octahedral sites of the spinel structure. Trace amounts of zinc-oxide and iron-oxide impurity phases were found for the samples with high Zn content (x >= 0.6). The comparison of the particle sizes obtained from scanning electron micrographs and the crystallite sizes estimated from XRD results suggest that the particles are polycrystalline aggregates of a few crystalline grains. Fourier transform infrared (FTIR) spectroscopy confirmed the presence of broad (vibrational) absorption bands between similar to 510 and 800 cm(-1) (v(1)) corresponding to tetrahedral complexes and between similar to 250 and 510 cm(-1) (v(2)) corresponding to octahedral complexes in the spinel structure of the Li-Zn ferrites. The phase compositions of the samples were obtained from the analysis of Mossbauer spectra and XRD patterns. Substitution of higher amount of Zn2+ ions reduces the saturation magnetization of the samples. Our work demonstrates that combustion synthesis method is a cost effective and simple way to synthesize bulk amount of Li-Zn ferrite samples with desired physical properties

High energy oxygen ion induced modifications in lead based perovskite thin films

The lead based ferroelectric PbZr0.53Ti0.47O3 (PZT), (Pb0.90La0.10)TiO3 (PLT10) and (Pb0.80La0.20)TiO3 (PLT20) thin films, prepared by pulsed laser ablation technique, were studied for their response to the 70 MeV oxygen ion irradiation. The dielectric analysis, capacitance-voltage (C- V) and DC leakage current measurements were performed before and after the irradiation to high-energy oxygen ions. The irradiation produced considerable changes in the dielectric, C-V, leakage characteristics and induced some amount of amorphization. The PZT films showed partial recrystallization after a thermal annealing at 400 degrees C for 10 min. The phase transition temperature [T-c] of PLT20 increased from 115 degrees C to 120 degrees C. The DC conductivity measurements showed a shift in the onset of non-linear conduction region. The current density decreased by two orders of magnitude after irradiation. After annealing the irradiated films at a temperature of 400 degrees C for 10 min, the films partially regained the dielectric and electrical properties. The results are discussed in terms of the irradiation-induced amorphization, the pinning of the ferroelectric domains by trapped charges and the thermal annealing of the defects generated during the irradiation. (C) 2007 Elsevier B.V. All rights reserved

Synthesis and thermal expansion hysteresis of Ca1-xSrxZr4P6O24

The low thermal expansion ceramic system, Ca1-xSrxZr4P6O24, for the compositions with x = 0, 0.25, 0.50, 0.75 and 1 was synthesized by solid-state reaction. The sintering characteristics were ascertained by bulk density measurements. The fracture surface microstructure examined by scanning electron microscopy showed the average grain size of 2.47 mum for all the compositions. The thermal expansion data for these ceramic systems over the temperature range 25-800degreesC is reported. The sinterability of various solid solutions and the hysteresis in dilatometric behaviour are shown to be related to the crystallographic thermal expansion anisotropy. A steady increase in the amount of porosity and critical grain size with increase in x is suggested to explain the observed decrease in the hysteresis

Radiation resistance of PFN and PNM-PT relaxor ferroelectrics

The relaxor ferroelectric compositions Pb(Fe1/2Nb1/2)O-3 (PEN) and [Pb(Mg1/3Nb2/3)O-3](0.8)-[PbTiO3](0.2) (PMN-PT) are studied for their radiation response to the high energy heavy ions (50 MeV Li3+, fluence 1 X 10(13)-1 X 10(14) ions/cm(2)) in terms of their structural, dielectric and piezoelectric properties. There was no change in the crystallinity of both the compositions after irradiation as seen from the XRD. The PEN composition did not show much change in the dielectric constant but the value of T-m decreased by 8degreesC. The PMN-PT composition showed an increase in the dielectric constant with increase in the irradiation fluence from 1 x 10(13) to 1 X 10(14) ions/cm(2) with no change in the value of T-m. The piezoelectric coefficient decreased in both the samples after irradiation. Among the compositions studied, PEN is observed to be more radiation resistant to changes in structural and dielectric properties than PM-PT. (C) 2003 Elsevier Ltd. All rights reserved

Ac conductivity studies on the Li irradiated PZT and SBT ferroelectric thin films

Pb(Zr_{0}_{.53}Ti_{0}_{.47})O_{3 }(PZT) and $SrBi_{2}Ta_{2}O_{9 }$(SBT) ferroelectric thin films were prepared on Pt coated Si substrates by pulsed laser ablation technique and their responses to the high energy Lithium ion irradiation were studied in terms of their ac conductivity, dielectric studies, polarization hysteresis and structural properties. The PZT and SBT thin films were fabricated in Metal/ Insulator-Metal capacitor configuration and were irradiated with the 50 MeV Lithium ions with varying fluence from $1*10^{12}$ to $1-10^{14}$ions cm^-^2. The ferroelectric properties were observed to be degraded by the irradiation. The ac conductivity of the films was explained by the charge carrier hopping model. Irradiated PZT thin films exhibited a significant variation on the frequency dependent exponent(s) while the irradiated SBT thin films had a negligible influence. The activation energy calculated from the Arrhenius plots was found to increase from 1.05 to 1.55 eV for PZT and from 0.85 to 0.91 eV for SBT thin film after irradiation. These energies were attributed to the oxygen vacancies and the deep trap carriers induced by the irradiation

High Energy Oxygen Ion Induced Modifications in Ferroelectric SrBi2Ta2O9SrBi_{2}Ta_{2}O_{9} Thin Films

The effects of high energy oxygen ion irradiation on the ferroelectric properties of $SrBi_{2}Ta_{2}O_{9}$ (SBT) thin films are reported. The films were grown using pulsed laser ablation. Fluence dependant degradation in the ferroelectric properties was observed. The dielectric constant did not show any frequency dispersion in both the unirradiated and irradiated films. After irradiation, the films showed only a decrease in the capacitance value retaining their ferroelectric nature. The switching voltages increased with broader peaks and showed a partial recovery after annealing of the irradiated film. A slim hysteresis loop with decreased $P_{s}$, $P_{r}$ and $E_{c}$ values was observed. The current density increased to a larger extent. The decrease in the dielectric constant, capacitance and polarization values was to a lesser extent as compared to those of PZT thin films under identical irradiation conditions. The results presented in this paper are illustrative of the fact that the layered perovskites have a stable structure and are less sensitive to extrinsic effects. The relatively high resistance of bismuth layered perovskites such as SBT to the high energy radiation along with the greater fatigue endurance as compared to PZT make them better candidates for applications in memory devices

Annealing temperature dependent structural and magnetic properties of MnFe2O4 nanoparticles grown by sol-gel auto-combustion method

Manganese ferrite (MnFe2O4) nanoparticles were synthesized by sol-gel auto-combustion method using manganese nitrate and ferric nitrate as precursors and citric acid as a fuel. Scanning electron micrographs show irregularly shaped morphology of the particles. The as-prepared samples were annealed at 400, 500, 600 and 800 degrees C for 2 h in air. The phase identification and structural characterizations were performed using powder X-ray diffraction technique along with Mossbauer spectroscopy. Magnetization loops and Fe-57 Mossbauer spectra were measured at RT. After annealing the sample at or below similar to 500 degrees C, we observed two different spinel phases corresponding to two different lattice parameters. This is originating due to the partial oxidation of Mn2+ to Mn3+. At high annealing temperatures (similar to 600 degrees C or above) the spinel MnFe2O4 phase decomposes into crystalline alpha-Mn2O3 and alpha-Fe2O3 phases, and amorphous FeO phase. (c) 2017 Elsevier B.V. All rights reserved