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Nanocrystalline samples of ZnCr0.4Fe1.6O4ferrite were synthesized by the advanced sol–gel method to investigate the effect of 200 MeV Ag+15ion irradiation on the cation distribution, magnetic and dielectric properties. Rietveld profile refinement of the X-ray diffraction (XRD) patterns confirms the single-phase cubic spinel structure of the specimens. The irradiated sample retains the cubic spinel structure with a slight increase in the lattice parameters and the average crystallite size. Temperature- and field-dependent dc magnetization studies show an appreciable enhancement in the saturation magnetization and blocking temperature of the irradiated samples, which could be attributed to the slight increase in the particle size due to the heat evolved during irradiation. Subsequently, the rearrangement of cations in the lattice structure and the ion-induced modifications on the surface states of the nanoparticles could be accountable. The room temperature dielectric constant and the loss tangent in the frequency range 75 kHz–10 MHz revealed the normal frequency dispersion. The increase in ϵrand tan δ on irradiation could be attributed to the slight crystal growth and hence the availability of the sufficient number of Fe2+and/or Zn3+ions particularly at the octahedral site on the grain boundaries, showing a fair agreement with the magnetization results. [ABSTRACT FROM AUTHOR]

Herein, the dielectric properties such as permittivity (real part ε ′ and imaginary part ε ′′) and dielectric loss tangent (tan δ ) are reported for Zn substituted Cu ferrites (Cu 1− x Zn x Fe 2 O 4 ; 0≤ x ≤1) composite using the sol–gel auto-combustion method. The variations of real and imaginary part of dielectric constant, tan δ and AC conductivity ( σ ac ) are studied at room temperature in the frequency range of 100 Hz–120 MHz. The real part of dielectric constant decrease with increasing frequency and the imaginary part ( ε ′′) varies with frequency showing the characteristic peak for each sample. The relation of tan δ with frequency shows relaxation spectra. Further, the σ ac tended to increase with increase in frequency. The variation in dielectric constant may be explained on the basis of space charge polarization, according to Maxwell and Wagner two-layer model. The dielectric constant and tan δ as a function of temperature are also studied with different temperatures ranging from 323 K to 583 K. [ABSTRACT FROM AUTHOR]

Abstract: Measurements of effective thermal conductivity (λ e) and effective thermal diffusivity (χ e) of twin pellets of Zn x Te100−x (x =5, 10, 30 and 50) chalcogenide materials, prepared under load of 5tons (equivalent pressure ≈433MPa) have been made simultaneously at room temperature using transient plane source (TPS) technique. Specific heat per unit volume (C p ) has also been determined from the so obtained data of λ e and χ e. The material has been prepared by melt quenching method. The results indicate that both the values of λ e and χ e increase logarithmically with increasing Zn concentration. This behaviour of λ e and χ e with zinc concentration can be explained by change of bond formation from covalent to ionic in this system. An effort has also been made to predict these values by an empirical relation. X-ray diffraction (XRD) studies for structural investigation of ZnTe have also been carried out and found to be polycrystalline in nature. [Copyright &y& Elsevier]