http://nopr.niscair.res.in/handle/123456789/1946 Search the Channel search http://nopr.niscair.res.in/simple-search http://nopr.niscair.res.in/handle/123456789/1978 Title: Nonlinear wave propagation in ferroelectric/ferrite interface <br/> <br/>Authors: Augustine, Michael; Pius, Roji; Mathew, Sunny; Mathew, Vincent <br/> <br/>Abstract: The propagation of electromagnetic wave through the interface of magnetized ferrite and nonlinear ferroelectric half-spaces has been theoretically studied. A dispersion relation for the wave propagation corresponding to the TE mode has been derived and numerically solved. It is observed that the propagation is non-reciprocal. The dependence of power on frequency has also been evaluated. <br/> <br/>Page(s): 211-214 http://nopr.niscair.res.in/handle/123456789/1977 Title: Low frequency dielectric dispersion studies in ferroelectric ceramics of Pb₀․₇₇K₀․₂₆Li₀․₂Ti₀․₂₅Nb₁․₈O₆ <br/> <br/>Authors: Rao, K Sambasiva; Krishna, P Murali; Prasad, D Madhava; Latha, T Swana; Satyanarayana, C <br/> <br/>Abstract: Temperature and frequency dependence of dielectric constant and conductivity properties of Pb₀․₇₇K₀․₂₆Li₀․₂Ti₀․₂₅Nb₁․₈O₆ (PKLTNO) ceramics are modeled through universal dielectric response (UDR). Partial substitution of Ti⁴⁺ in Nb⁵⁺ increased the B- sites ordering, supported by charge compensation and creation of oxygen vacancies that obeys Kroger-Vink notation. The release of electrons by this reaction are captured by the Nb⁵⁺ and Ti⁴⁺ to generate Nb³⁺ and or Ti³⁺. Thus the possibility of the hopping of electrons among Nb⁵⁺ and Nb³⁺ and Ti⁴⁺ and Ti³⁺ entering in the crystal structure participate in the conductivity. The dielectric characterization is performed from room temperature to 590°C, in the frequency range of 45 Hz-5 MHz. The measured dielectric constant has been found to fit to Jonscher’s dielectric dispersion relations: Ɛ' = Ɛ∞ + sin(n(T)л/2) (a(T)/ Ɛ0) (ω ⁿ(T)⁻¹) and Ɛ" = σ/i Ɛ0 ω + cos(n(T)л/2) (a(T)/ Ɛ0) (ωⁿ(T)⁻¹). Cole-Cole plots are found inclined at an angle (1-n(T))X л/2 which obeys the universal material behaviour Ɛ∞ + A(T) (ωⁿ (T) ⁻¹). The exponent n(T) and coefficient A(T) = [a(T)S/L] has been observed to be minimum and maximum respectively at TC~425°C. The conductivity studies reveal the conduction in the material arisising due to hopping of bound charges. <br/> <br/>Page(s): 215-223 http://nopr.niscair.res.in/handle/123456789/1975 Title: Dielectric properties of In-Se-Te glassy alloys <br/> <br/>Authors: Maan, A S; Goyal, D R <br/> <br/>Abstract: In this paper, the dielectric properties of In₄₀SexTe₆₀₋x glassy alloys (x = 10, 20 & 30) have been reported. These measurements are carried out as a function of temperature and frequency in the range 120-350 K and 0.1-10 kHz respectively. The frequency and temperature dependence of dielectric constant Ɛ΄ and dielectric loss Ɛ΄΄ is almost similar in nature in all the alloys and the experimental results indicate that dielectric dispersion sets in at temperature exceeding 150 K and is more prominent at lower frequencies. Ɛ΄ and Ɛ΄΄ values as a function of temperature and frequency are maximum for x = 20 alloy, though similar behaviour is observed in all the samples. The experimental results seem to be explained in terms of the theory of dielectric dispersion based on two electrons hopping over a potential barrier. The frequency dependence of dielectric loss in present set of glasses at a fixed temperature is in good agreement with theory of dielectric dispersion. <br/> <br/>Page(s): 207-210 http://nopr.niscair.res.in/handle/123456789/1974 Title: Structural and dielectric properties of LaBi₂Fe₅O₁₂ <br/> <br/>Authors: Jawahar, K; Choudhary, R N P <br/> <br/>Abstract: The polycrystalline sample of LaBi₂Fe₅O₁₂ (LBIG) distorted perovskite compound is prepared using a high-temperature solid-state reaction technique. Room temperature preliminary X-ray diffraction (XRD) studies of the compound show the tetragonal splitting. It confirms the formation of single-phase compound with 2% of pyrochlore phase. The elemental content of the compound has been verified by energy dispersive spectroscopy (EDS) microanalysis. Microstructural analysis by scanning electron microscopy (SEM) shows that the grains are homogeneously as well as uniformly distributed throughout the surface of the sample. Dielectric studies as a function of temperature (30-360C) at four different frequencies (1, 10, 100, 1000 kHz) yielded a dielectric anomaly at 325C. It is interesting to note that the loss tangent (tan δ) seems to be reduced at higher frequencies after reaching the instrumental saturation. Also, dielectric measurement as a function of frequency (100 Hz-1 MHz) at room temperature reveals the presence of different types of polarization mechanisms involved in the material. Again the frequency dependent loss tangent (tan δ) shows the sinusoidal variation, which is unusual for this kind of measurement. This variation has been confirmed by repeating the measurement at various temperatures. <br/> <br/>Page(s): 203-206