Study of the dielectric parameters of aluminium ore bauxite of Mainpat area of Chhattisgarh at X-band frequency

A simple method for measuring the dielectric parameter of materials in the form of powders at microwave frequencies is suggested. Measurement of the permittivity ε′ and ge″ at 9·967 GHz on powder samples of the aluminum ore bauxite gives interesting results. It is found that ε′ and ε″ increases with packing densities (δ ). Further ε′ and ε″ also depend upon the percentage of Al₂O₃. These results show that the values of ε′ and ε″ can be used to set certain basic values for minability of the ore for a particular sample. Conductivities (σ) and relaxation (τ) are also calculated in the present studies     

Study of the characteristics of the soil of Chhattisgarh at X-band frequency

The real and imaginary parts (ε₁ and ε₂) of the complex dielectric constant (ε) of sand, silt and clay with varied moisture content have been determined experimentally under laboratory conditions at 9·967 GHz. using infinite sample method. The values of (ε₁) and (ε₂) first increase slowly with moisture content upto a certain transition point and then increase rapidly with moisture content     

Dielectric relaxation in Se<Subscript>80−<Emphasis Type="Italic">x</Emphasis></Subscript>Te<Subscript>20</Subscript>Sn<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> chalcogenide glasses

This study reports the temperature and frequency dependence of dielectric constant (ε′) and dielectric loss (ε′′) in glassy Se_80−x Te₂₀Sn _x (x = 0, 2, 4, 6) alloys. The measurements have been made in the frequency range (1–500 KHz) and in the temperature range 305–335 K. The results indicate that the dielectric dispersion exists in the present glassy systems in the above frequency and temperature range. The composition dependence of the dielectric constant, dielectric loss and activation energy thermally activated crystallization is also discussed.     

Impact of metal filler on the dielectric properties of Nylon 11

Dielectric measurements of pure Nylon 11 in comparison with metal (Zn) filled Nylon 11 have been carried out using an impendence analyzer in the frequency range of 10²–10⁷ Hz and temperature range 20–120 °C. Two different concentrations (1% and 5% (w/w)) of metal (Zn) fillers were used. It was observed that at low frequencies and particularly at high temperature dielectric permittivity (ε′) for 1% Zn filled sample is more than that of pure Nylon 11 whereas ε′ for 5% Zn filler is less as compared to that for pure Nylon 11. But at very high frequencies dielectric permittivity (ε′) for pure Nylon 11 is less than Zn filled samples. Also it is found that for all frequencies and particularly at high temperature ε′′ as well as tan δ are maximum for pure Nylon 11 and decrease for filled Nylon 11 samples. The Cole–Cole arcs have also been plotted for these samples. Using these plots the static and instantaneous values of dielectric permittivity and orientation polarization parameter ‘S’ have been calculated.     

Frequency-dependent dielectric and electric modulus properties of Li–Ni–Sm–Fe–O spinel embedded in conducting polymer

Conducting polymeric nanocomposite containing Li–Ni–Sm–Fe–O spinel was synthesized by the chemical oxidizing of aniline in the presence of LiNi_0.5Sm_0.08Fe_1.92O₄ particles. The dielectric and electric modulus properties of the as-prepared samples were investigated over a frequency range from 10⁶ to 10⁹ Hz. The dielectric constant (ε′), dielectric loss (ε″) and dissipation factor (tan δ) for all samples presented relatively high values at low frequency and were found to decrease with the frequency. The values of ε′, ε″ and tan δ of the nanocomposite were lower than that of the pristine PANI. Electric modulus analysis had been carried out to understand the electrical relaxation process. The dielectric relaxation time for the nanocomposite became longer due to the introduction of LiNi_0.5Sm_0.08Fe_1.92O₄ particles lowering the crystallinity of PANI.     

Dielectric properties of a ceramic oxide: Li(Ni<Subscript>7/10</Subscript>Fe<Subscript>3/10</Subscript>)VO<Subscript>4</Subscript>

The Li(Ni_7/10Fe_3/10)VO₄ compound has been synthesized by solution-based chemical route. Its dielectric response is investigated using complex impedance spectroscopy technique. Frequency dependence of dielectric constant (ε_r) at different temperatures shows low-frequency dispersion due to polarized structure of the material and mobile charge carriers. Temperature dependence of ε_r at different frequencies exhibits the dielectric anomalies in ε_r at different temperatures. Dielectric relaxation process in the material is signified by the variation of tangent loss with frequency at different temperatures. The variation of relaxation time with temperature obeys the Vogel–Fulcher law.     

Synthesis and dielectric properties of MXTi<Subscript>7</Subscript>O<Subscript>16</Subscript> (M = Ba and Sr; X = Mg and Zn) hollandite ceramics

MXTi₇O₁₆ (M = Ba and Sr; X = Mg and Zn) ceramics have been synthesized by the conventional solid state ceramic route. The dielectric properties such as dielectric constant (ε_r), loss tangent (tan δ) and temperature variation of dielectric constant (τ_εr) of the sintered ceramic compacts are studied using an impedance analyser up to 13 MHz region. The strontium compounds have relatively high dielectric constant and low loss tangent compared to the barium analogue. The phase purity of these materials has been examined using X-ray diffraction studies and microstructure using SEM method.     

Dielectric behaviour of erbium substituted Mn-Zn ferrites

Dielectric properties such as dielectric constant (ε′) and dielectric loss tangent (tan□δ) of mixed Mn-Zn-Er ferrites having the compositional formula Mn_0.58Zn_0.37Fe_2.05−xEr_x0₄ (where itx = 0.2, 0.4, 0.6, 0.8 and 1.0) were measured at room temperature in the frequency range 1–13 MHz using a HP 4192A impedance analyser. Plots of dielectric constant (ε′) vs frequency show a normal dielectric behaviour of spinel ferrites. The frequency dependence of dielectric loss tangent (tan δ) was found to be abnormal, giving a peak at certain frequency for all mixed Mn-Zn-Er ferrites. A qualitative explanation is given for the composition and frequency dependence of the dielectric constant and dielectric loss tangent. Plots of dielectric constant vs temperature have shown a transition near the Curie temperature for all the samples of Mn-Zn-Er ferrites. However, Mn_0.58Zn_0.37Er_1.0Fe_1.05O₄ does not show a transition. On the basis of these results an explanation for the dielectric mechanism in Mn-Zn-Er ferrites is suggested.     

Dielectric studies of tin based chalcogenide glasses

The dc conductivity and dielectric parameters of glassy system of a-Se₇₀Te_30−x Sn _x (x = 0, 2, 4, 6, 8 and 10) glasses have been investigated. Frequency and temperature dependence of dielectric constants (ε′) and dielectric loss (ε′′) are studied in the frequency range 120–100 kHz and temperature range 300–390 K. Dielectric dispersion is observed when Tin (Sn) is incorporated to a-Se–Te system in the entire temperature range. These results explain that the dc conduction loss is dominated in the present system. From dc conductivity studies it is observed that the dc conductivity and activation energy increases with increasing tin concentration in the present system.     

On the compound- LiNi3/5Fe2/5VO4 for dielectric response

The LiNi_3/5Fe_2/5VO₄ has been prepared by solution-based chemical method. An orthorhombic unit cell structure with lattice parameters a = 3.7778 ?, b = 15.8244 ? and c = 5.5629 ? is confirmed by X-ray diffraction. Frequency dependence of dielectric constant (ε_r) at room temperature indicates the features of dielectric material. Temperature dependence of tangent loss at some selected frequencies shows the presence of dielectric relaxation phenomena in the material. Dielectric anomalies in ε_r at different temperatures are studied by temperature dependence of ε_r at some selected frequencies. The variant of relaxation time with temperature follows the Vogel-Fulcher relation.     

Determination of electrodynamic parameters of materials over a wide frequency range

We generalize experimental and theoretical material on investigation of the frequency dependence of magnetic permeability μ, dielectric permeability, ε and specific electrical conductivity σ in the 0–10 Hz range for a broad class of material and media with normal dispersion. We obtain analytic relations characterizing the relationship of the parameters μ, σ and ε in the indicated frequency range. Translated from Izmeritel'naya Tekhnika, No. 9, pp. 10–13, September, 1997.     

A note on ‘ferroelectricity in polymer films containing TGS powder’

Ferroelectric polymer films have been made by dispersingtgs powder. The dielectric constant ε′ of the films has been measured. The thermal behaviour of ε′ is also reported. Data have been obtained from samples prepared with different weight concentrations (10–75%) oftgs.     

Dielectric properties of Be(IO<Subscript>3</Subscript>)<Subscript>2</Subscript>⋅4H<Subscript>2</Subscript>O crystals

The article studies the dielectric properties, dc conductivity and ac conductivity of Be(IO₃)₂⋅4H₂O single crystals. The dielectric constant ε has been defined for the three directions of the vectors a, b and c in the crystals in the temperature interval 280–340 K and frequency range 100 Hz–10⁶ Hz. The crystals show strongly expressed anisotropy, at 20 ^∘C and frequency 100 Hz ε_a = 235, ε_b = 30 and ε_c = 85. The frequency dependence of ε is evidence of the presence of low-frequency relaxation polarization in the crystals. The activation energies of the three directions in the crystals have been derived from the temperature dependence of dc conductivity, and they are 1.03 eV, 0.836 eV and 1.2 eV respectively.     

Compound-LiCo<Subscript>3/5</Subscript>Fe<Subscript>1/5</Subscript>Mn<Subscript>1/5</Subscript>VO<Subscript>4</Subscript> and dielectric characteristics

The LiCo_3/5Fe_1/5Mn_1/5VO₄ compound was successfully synthesized by solution-based chemical method. The variation of dielectric constant (ε_r) with frequency at different temperatures shows a dispersive behavior at low frequencies. Temperature dependence of ε_r at different frequencies indicates dielectric anomalies in ε_r at temperature (T_max) = 220, 235, 245, 260 and 275 °C with (ε_r)_max ~ 6,830, 2,312, 1,224, 649 and 305 for 10, 50, 100, 200 and 500 kHz, respectively. The variation of tangent loss with frequency at different temperatures shows the presence of dielectric relaxation in the material. The variation of relaxation time as a function of temperature follows the Vogel-Fulcher relation.     

Dielectric and impedance spectroscopy studies on sisal fibre-reinforced polyester composite

Frequency and temperature dependence of dielectric constant (ε_r), dielectric loss (tanδ), ac conductivity (σ_ac) and complex impedance spectroscopy studies on cured polyester matrix and sisal fibre-reinforced polyester composites (SFRPC) have been investigated in the frequency range from 180 Hz to 1 MHz and temperature range from room temperature to 200 °C. The experimental results showed that with the incorporation of sisal fibre, the values of ε_r, tanδ and σ_ac are increased. It is also found that the values of ε_r and tanδ for both cured polyester matrix and SFRPC are decreased with increasing frequency, which indicates that the major contribution to the polarization may come from orientation polarization and interfacial polarization. The increasing value of ε_r with increasing temperature at a particular frequency is due to free motion of the dipole molecular chains within the cured polyester matrix and SFRPC at higher temperature.     

Impedance-spectroscopy analysis of oriented and mercerized bamboo fiber-reinforced epoxy composite

Bamboo fiber-reinforced epoxy composites were fabricated with untreated and alkali treated bamboo fibers. Dielectric, electric modulus, ac, and dc conductivity studies were carried out to rationalize the dielectric behavior of bamboo/epoxy composites. Composites of two fiber orientation parallel and perpendicular to the electric field were prepared. The dielectric behavior and electric modulus spectra of the composites were characterized using standard impedance analyzer. Dielectric properties were analyzed as a function of frequency (95 Hz–2 MHz) for temperatures in the range from 30 to 180 °C. Real part of dielectric constant (ε′), conductivity, and dielectric dissipation factor (tan δ) of 0° oriented bamboo/epoxy composites were higher than that of 90° oriented composites. Conductivity activation energy, tan δ, ε′, and volume resistivity decreased with increase in frequency at all the temperatures under study. Mercerization reduces the water absorption in bamboo fibers and thus improves corresponding dielectric properties of composites. Relaxation times 39.80 μs and 258.5 μs for 0° and 90° oriented bamboo/epoxy composites were calculated respectively from the relaxation peaks observed in electric modulus spectra at 180 °C.     

Electrical conductivity and dielectric properties of cadmium thiogallate CdGa<Subscript>2</Subscript>S<Subscript>4</Subscript> thin films

Cadmium thiogallate CdGa₂S₄ thin films were prepared using a conventional thermal evaporation technique. The dark electrical resistivity calculations were carried out at different elevated temperatures in the range 303–423 K and in thickness range 235–457 nm. The ac conductivity and dielectric properties of CdGa₂S₄ film with thickness 457 nm has been studied as a function of temperature in the range from 303 to 383 K and in frequency range from 174 Hz to 1.4 MHz. The experimental results indicate that σ_ac(ω) is proportional to ω ^s and s ranges from 0.674 to 0.804. It was found that s increases by increasing temperature. The results obtained are discussed in terms of the non overlapping small polaron tunneling model. The dielectric constant (ε′) and dielectric loss (ε″) were found to be decreased by increasing frequency and increased by increasing temperature. The maximum barrier height (W _m) was estimated from the analysis of the dielectric loss (ε″) according to Giuntini’s equation. Its value for the as-deposited films was found to be 0.294 eV.     

Magnetic and Dielectric Properties of <Emphasis Type="Italic">R</Emphasis><Subscript>2</Subscript>CuTiO<Subscript>6</Subscript> Compounds (<Emphasis Type="Italic">R</Emphasis>=Y,La, Pr and Nd)

Magnetic and dielectric properties of the double perovskite compounds of the type R ₂CuTiO₆ (RCTO, where R=Y, La, Pr and Nd) has been studied. Y₂CuTiO₆ (YCTO) crystallizes in a hexagonal unit cell, whereas the other three compounds form into orthorhombic structure. All four compounds show paramagnetic behavior down to 5 K. The dielectric studies show moderate dielectric constant (ε′) and very small dielectric loss (tan δ) for YCTO. The orthorhombic members of RCTO compounds exhibit moderate values of ε′ and tan δ. The dielectric properties are presented and discussed here in the light of the influence of structure and rare-earth ions on the physical properties of RCTO compounds.     

Dielectric properties of carbon black: SBR composites

A series of styrene–butadiene rubber (SBR) composites have been prepared with different weight ratios of polyacetylene based conducting carbon black (CCB) (0–90 phr). The SBR–CCB systems are characterized for dimensional stability which is enhanced by increasing the CCB loading because of enhancement in polymer-filler interaction. The electrical properties such as dielectric constant (ε_r), dissipation factor (tan δ) and dielectric loss (ε″) of the composites have been studied. The influence of different loading of CCB (0–90 phr), frequency of ac (100 Hz–30 MHz) and temperature (25–75 °C) on the electrical properties was studied. An increase in dielectric constant and tan δ of the SBR composites was observed with increase in CCB content and ac frequency. This is due to enhancement of filler–filler interaction and the increase in continuity of conducting phase. The surface morphology has been studied using scanning electron microscopy (SEM).     

Dielectric characteristic and local phase transition of gallium phosphide nanosolid

The dependences of relative dielectric permittivity, ε′ _r, and tangent of dielectric loss angle, tg δ, of gallium phosphide (GaP) nanosolid on frequency and temperature were investigated. The GaP nanopowders are subglobular in shape, with the average crystallite size of about 50 nm evaluated from Scherrer equation. It can be concluded that the leakage current mechanism plays an important role in the dielectric loss of the GaP nanosolid. The dielectric characteristic of the GaP nanosolid in the range 298–350 K allows to detect an ε′ _r or tg δ peak at 303 K that is due to local phase transitions, probably in the high hydrostatic stress field of dislocations with an edge component. Under the influence of an electric field, the high hydrostatic stress field of dislocations can undergo changes in deformation, accompanied by drastic stress-induced changes in the order parameter near the phase transition temperature, and hence, changes in the Gibbs free energy per unit volume can be found.