Investigation of the conductivity of Na2SO4–PbTiO3 composite electrolyte system: Non linear electrical behavior at Curie temperature of the dispersoid (original) (raw)
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Electrical properties of Na2SO4-based composite systems
Ionics, 2007
Composite electrolytes are well-known multiphase systems and exhibit maxima in the conductivity at certain second-phase concentration. An attempt has been made to investigate a number of sodium sulfate (Na 2 SO 4)based composite systems. The dispersoids that have been used are MgO, Al 2 O 3 , and SiO 2. The samples have been characterized using impedance spectroscopy, X-ray diffraction, and differential scanning calorimetry. The maximum conductivity has been observed for MgO dispersed system, and the percolation threshold has been observed at 30-mol% dispersoid, MgO concentration. Interestingly, two maxima have been observed in case of the Na 2 SO 4-SiO 2 and Na 2 SO 4-Al 2 O 3 composite systems. In the Na 2 SO 4-SiO 2 system, the first maximum occurs at lower concentration, i.e., in the range between 10 and 20 mol%, whereas the second occurs at the 40-mol% dispersoid concentration. For the Na 2 SO 4-Al 2 O 3 system, although slightly indistinguishable, two peaks in the conductivity vs composition plot have been observed around 12-and 30-mol% Al 2 O 3 concentrations.
Journal of Solid State Chemistry, 2000
A moderate increase in the electrical conductivity of sodium sulfate has been obtained by dispersing alumina particles. The largest enhancement in conductivity for furnace-cooled samples is observed for 5.5 and 35 m/o-Al 2 O 3 compositions. For 35 m/o composition, the conductivity increases by more than 1 order of magnitude at 4003C and 2 orders of magnitude at 2003C. In contrast to the understanding based on many composite electrolyte theories, 0.004 m alumina brings about the same or even lower enhancement in conductivity as 0.5 m alumina. Furthermore, contrary to expectations, negligible enhancement is observed when-Al 2 O 3 is employed. The maximum enhancement in this study is observed for the 4 m/o Al 2 O 3 quenched sample: the conductivity increases by 2 orders for the high-temperature phase and by more than 3 orders for the low-temperature phase. 2000 Academic Press
Na2SO4–Al2O3 composite electrolytes: some interesting observations
Materials Research Bulletin, 2000
In the Na 2 SO 4-Al 2 O 3 system, the variation in electrical conductivity with composition and dispersoid size stands in stark contrast to that of most other reported composite systems. Two maxima, instead of one, are observed in the conductivity vs. composition plot, at 5.5 and 35 mol% Al 2 O 3. Maximum conductivity enhancement is observed for 35 mol% Al 2 O 3. The increase is about 20 times at 400°C and 450 times at 200°C. Possible conductivity enhancement mechanisms operating in this system are suggested. Surprisingly, the reduction in alumina particle size from 0.5 to 0.004 m does not bring about any further enhancement in conductivity.
Physica B: Condensed Matter, 2019
By using the semi-wet synthesis method, lead-free ferroelectric materials Ba0.9Sr0.1Ti1-xSnxO3 with x = 0, 0.02, 0.05, and 0.10 (abbreviated as BSTS) were prepared and their structural, electric and electrocaloric properties were investigated. The X-ray diffraction (XRD) patterns show that the samples calcined at 950°C have well crystallized into perovskite structure suggesting the substitution of Ti 4+ by Sn 4+ in BST lattice. With increasing content of Sn, the enhancement of the dielectric permittivity was observed for (0≤x≤0.05) and the ferroelectric transition temperature (TC) was found to shift towards the room temperature (TC = 20°C for x = 0.10). Direct measurements of the electrocaloric effect (ECE) were performed on all samples by using the highresolution calorimeter. It is found that Ba0.9Sr0.1Ti0.95Sn0.05O3 exhibits a high ECE temperature change of TEC = 0.188 K at an applied electric field of only 7 kV/cm. Impedance spectrum analysis of all the samples performed in the temperature range of 300-360°C reveals the existence of two relaxation contributions related to the grain and grain boundaries that are well separated in frequency. Activation energies of conduction and relaxation processes were deduced for both contributions in order to determine the conduction mechanism of the studied compositions.
Journal of Alloys and Compounds, 2015
Polycrystalline samples of (1 À x)(Na 0.4725 K 0.4725 Li 0.055 NbO 3) À x(BiFe 0.5 Ta 0.5 O 3) (where x = 0.005 and 0.007 were prepared by using a solid state reaction technique. The XRD patterns of the samples at room temperature shows perovskite phase with monoclinic structure. The dielectric constant for x = 0.007 is maximum. Detailed studies of dielectric and impedance properties of the materials in a wide range of frequency (100 Hz-1 MHz) and temperatures (RT-500°C) shows that dielectric properties were strongly temperature and frequency dependent. Dielectric and electrical properties of samples, indicate that the Curie temperature shifted to higher temperature side with the increase in frequency. The AC conductivity also increases with increase in frequency. The low value of activation energy obtained for the ceramic samples could be attributed to the influence of electronic contribution to the conductivity. The plots of Z 00 and M 00 vs frequency at various temperatures shows peaks in the higher temperature range (>320°C). The compounds show dielectric relaxation, which is found to be of non-Debye type and the relaxation frequency shifted to higher side with increase in temperature. The Nyquist plot and conductivity studies showed the NTCR character of samples.
Informacije Midem-journal of Microelectronics Electronic Components and Materials, 2015
We report the specific heat capacity and thermal conductivity of electrocaloric (1-x)Pb(Mg 1/3 Nb 2/3)O 3-xPbTiO 3 (x = 0, 0.1, 0.3 and 0.35) ceramics between room temperature and 300 °C. The specific heat capacity for all ceramic samples is between 0.323 and 0.326 J/gK at 35 °C. For the samples with a high PbTiO 3 content (x = 0.3 and 0.35), a pronounced anomaly is observed in the specific heat capacity versus temperature at 130 °C and 153 °C, indicating the phase transition from the polar to a non-polar phase. The thermal conductivity in this system significantly depends on the PbTiO 3 content. The lowest thermal conductivity is obtained for Pb(Mg 1/3 Nb 2/3)O 3 , and it increases with increasing PbTiO 3 content in the whole temperature range. For example at 23 °C the values of thermal conductivity of Pb(Mg 1/3 Nb 2/3)O 3 and 0.65Pb(Mg 1/3 Nb 2/3)O 3-0.35PbTiO 3 are 1.25 W/mK and 1.43 W/mK, respectively.
Journal of Physics and Chemistry of Solids, 2005
The dependence of loss tangent (tanδ) and relative permittivity (εr) on temperature and frequency has been reported for Na2-XKXTi3O7 (with X=0.2, 0.3, 0.4) ceramics. The losses are characteristic of dipole mechanism and electrical conduction. The peaks of εr at high temperature indicate a possible ferroelectric phase transition for all three compositions. The results of a.c. conductivity studies on the same samples have also been reported. The corresponding ln(σT) versus 1000/T plots have been divided into five regions namely I, II, III, IV and V. The various conduction mechanisms in the different regions have been stressed. Furthermore, the log(σ) versus frequency plots for all the above samples reveal that the electronic hopping (polaron) conduction, which diminishes with the rise in temperature, is dominant in the lower temperature region. The interlayer ionic conduction seems to play a major role in conduction towards higher temperature.
Journal of Crystallization Process and Technology, 2012
Nano-composite, perovskite Ba (1-x-y) Sr (x) TiFe (y) O 3 , denoted as (BSTF) in powder form was derived via sol-gel (SG) method followed by sintering at fixed temperature 750˚C for one hour. The morphology and structure of the powder samples were investigated by using X-ray diffraction (XRD), transmission electron microscope (TEM) and scanning electron microscope (SEM). The XRD characterization indicates formation of a tetragonal crystalline phase in the pure BST. A well defined perovskite phase with nano-crystallite sizes equal to about 32 nm was achieved from XRD for B10ST20F sample, while TEM study confirmed the obtained XRD results giving the following crystallite size value about 29.82 nm for the same sample. The dielectric A.C. conductivity was evaluated as a function of temperature and frequency ranging from 42 Hz up to 1 MHz.
Electrical Properties and AC Conductivity of (Bi 0.5 Na 0.5 ) 0.94 Ba 0.06 TiO 3 Ceramic
ISRN Ceramics, 2012
Lead-free perovskite (Bi0.5Na0.5)0.94Ba0.06TiO3(BNBT06) was prepared by conventional ceramic fabrication technique at 1160°C/3h in air atmosphere. The crystal structure, microstructure, dielectric, polarization, piezoelectric properties, and ac conductivity of the sample were studied. X-ray diffraction data confirmed the formation of a single phase tetragonal unit cell. Williamson-Hall plot was used to calculate the lattice strain and the apparent particle size. The experimental relative density of BNBT06 was found to be~96-97% of the theoretical one with an average grain size~4 μm. Room temperature dielectric constant and loss factor at 1 kHz were found to be equal to 781 and 0.085, respectively. Longitudinal piezoelectric charge coefficient of the poled sample under 2.5 kV/mm at 80°C in silicone bath was found to be equal to 124 pC/N. Complex impedance and electric modulus spectroscopic analyses showed the dielectric relaxation in the material to be of non-Debye type. The Nyquist ...