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This work presents the structural and the thermoelectric properties of wurtzite ZnO using ab-initio density functional theory (DFT) with GGA exchange-correlation functional. The relaxed lattice parameters are generated by variable cell relaxation method. The thermoelectric properties as a function of chemical potential are studied within constant relaxation-time approximation for different temperatures. The Seebeck co-efficient is found to be more for positive chemical potential where the major contribution is from electrons and it decreases with increase in temperature. The electrical conductivity, power factor and electronic thermal conductivity show enhanced values for p-type doping region and increases with rise in temperature. The figure of merit (ZT) is computed to be 0.98 which is adequate for thermoelectric applications. [ABSTRACT FROM AUTHOR]

Lead free ferroelectric ceramics of (K0.5Na0.5)(Nb1-xMnx)O3 (x = 0, 0.01) were prepared by solid state reaction technique and the effect of Mn doping on their crystal structure, dielectric and ferroelectric properties was investigated. Rietveld refinement on the XRD data was carried out using an orthorhombic crystal structure having Amm2 space group, suggesting the formation of single phase compounds. The temperature dependent dielectric properties for both the compounds show two phase transitions, one corresponding to orthorhombic to tetragonal (TO-T) phase transition and the other to the tetragonal to cubic phase transition (TC). An improved dielectric constant of 345 (at RT) and 5175 (at TC) in Mn doped KNN is observed compared to pure KNN (285 at RT and 4610 at TC). Ferroelectric properties measurement at room temperature indicates a significant enhancement of remnant polarization (2Pr) in Mn doped KNN (25.26 µC/cm2) ceramics with respect to pure KNN (16.38 µC/cm2). [ABSTRACT FROM AUTHOR]

We report the structural and magneto-dielectric properties of 0.95 Pb(Fe0.5Nb0.5)-0.05 Co0.6 Zn0.4Fe1.7Mn0.3O4 (0.95PFN-0.05CZFMO, PC5) particulate composite prepared using a hybrid synthesis technique. Rietveld refinement on the XRD patterns of the end compounds i.e. PFN and CZFMO were performed using monoclinic crystal structure with space group Cm and cubic crystal structure with space group Fd-3m respectively. The dual phase space group Cm+Fd-3m was taken to refine the XRD pattern of PC5 sample which confirms the formation of composite. The changes in the dielectric parameters by the application of magnetic field suggest existence of magneto-electric coupling behavior in the composite at room temperature (RT). The quantitative changes of the magneto-dielectric properties i.e. MC% (magneto- capacitance), ML% (magneto-loss), MI% (magneto-impedance) and MP% (magneto-phase) were calculated and discussed their dependence with magnetic fields at RT. [ABSTRACT FROM AUTHOR]

The Eu3+ doped phosphate based phosphors NaCdPO4 hosts were prepared by solid-state reaction. The effects of the crystalline host and the incorporation of a sensitizer Eu3+ on the luminescence characteristics of the specimen phosphors were studied. NaCdPO4 was investigated for its structural and luminescence properties, as a possible host material for efficient phosphors. Prepared phosphors were characterized by photoluminescence technique possesses a 320 nm excitation maxima and emission broad peak appears at 637 nm indicating a possible red phosphor for UV excitation operated white LED application. [ABSTRACT FROM AUTHOR]

Physical properties are known to be drastically varied with chemical pressure and crystallite size in a multifunctional material. In this context, various concentrations of Zn (0 ≤ x ≤ 0.2) in the Fe site of LaFeO3 are prepared by wet-chemical route. The average particle size is of the order of 40-50 nm. The concentration dependent electrical behavior and the conduction mechanism at room temperature have been studied in detail by cole-cole plot of the Impedance and modulus spectra. The high frequency depressed semi circles represent the grain conduction while the intermediate frequency semi circles appear may be due to grain boundary effect. [ABSTRACT FROM AUTHOR]

We report the structural, magnetic and dielectric properties of lightly Gd-substituted DyMnO3 (Dy0.95Gd0.05MnO3) prepared by acrylamide polymer gel template method. Rietveld refinement on powder X-ray diffraction (XRD) data were carried out using orthorhombic crystal structure with Pnmaspace group, which suggest the formation of single phase material. The temperature dependence magnetic susceptibility data indicates the existence of antiferromagnetic transition due to rare-earth ion and lock-in transition temperature. The magnetic properties study reveal the signature of antiferromagnetic behavior along with the existence of weak ferromagnetic component in low temperature region. The intrinsic dielectric behavior of the material was observed up to 160 K and above 160 K there is large increase in dielectric behavior, which may be due to contribution from extrinsic Maxwell-Wagner polarization phenomena. [ABSTRACT FROM AUTHOR]

Lead-free ferroelectric 0.7Ba(Zr0.2Ti0.8)O3-0.3(Ba0.7Ca0.3)TiO3 (BZT-BCT) ceramics have been prepared by sol-gel auto combustion technique. XRD pattern reveals the realization of single phase material. Rietveld refinement of the XRD patterns confirms the rhombohedral structure having space group R3m. FESEM micrograph shows a highly dense microstructure. The effect of electrical poling on ferroelectric properties and leakage current behavior discussed in detail. The variation of leakage current with the electric field is in consistent with the space charge conduction mechanism. [ABSTRACT FROM AUTHOR]

Detailed magnetic measurements of the Pr0.75Na0.25MnO3 polycrystalline sample have been carried out under external hydrostatic pressure upto 10kbar. Pressure strongly suppresses the first order magnetic transition, while thermal hysteresis narrows down progressively and then disappears with increase in pressure. The significant enhancement of the field cooled magnetization value at different pressures is due to the antiferromagnetic to ferromagnetic transformation, while ruling out any contribution from the domain alignment within the ferromagnetic phase. [ABSTRACT FROM AUTHOR]

Modified-PZT ceramics with a formula Pb0.9Ni0.1[(Zr0.52Ti0.48)]1-xSnxO3 located near the morphotropic phase boundary (MPB) were prepared by conventional solid state process to investigate effects of dilute doping of Ni and Sn in different sites of PZT. The single phase structure of the series of samples has been identified by x-ray diffraction technique. The optical band gap has been obtained from the UV-Vis spectra and found to be shrinkage with doping. The detail dielectric and impedance studies are being carried out to investigate the conduction mechanism of the samples. A significant enhancement in the electric polarization is observed for the maximum Sn doping in a modified PZT. [ABSTRACT FROM AUTHOR]

Simultaneous measurement of field dependent resistivity and dielectric permittivity has been carried out to observe the tunability of magnetoelectric phases of contrasting order in a charge order material Pr0.75Na0.25MnO3. The material is synthesized by wet chemical technique to reduce the volatilization of Na and avoid any precipitation of manganese oxide. The dielectric study reveals highly resistivity correlated dielectric behavior has been observed throughout the insulator to metal and vice versa transition. The metallic phase in the proximity of insulating phase enhances the functionality of this material with a several order in the magnetoelectric parameter. Furthermore, the Maxwell-Garnett theory is being used to analyze the field and temperature dependent dielectric anomaly. [ABSTRACT FROM AUTHOR]

Simultaneous measurement of field dependent resistivity and dielectric permittivity has been carried out to observe the tunability of magnetoelectric phases of contrasting order in a charge order material Pr0.75Na0.25MnO3. The material is synthesized by wet chemical technique to reduce the volatilization of Na and avoid any precipitation of manganese oxide. The dielectric study reveals highly resistivity correlated dielectric behavior has been observed throughout the insulator to metal and vice versa transition. The metallic phase in the proximity of insulating phase enhances the functionality of this material with a several order in the magnetoelectric parameter. Furthermore, the Maxwell-Garnett theory is being used to analyze the field and temperature dependent dielectric anomaly. [ABSTRACT FROM AUTHOR]

Nanostructured Bi2O3 was prepared through mechanical alloying method. Detailed microstructural information was obtained after Rietveld refinement of the prepared samples. The Transmission Electron Microscope images confirmed the crystallinity of the sample. The average crystallite size decreases whereas microstrain increases due to milling. The ionic conductivity of the milled sample was found to have increased few orders than the unmilled sample. The change in structural and electrical properties due to milling were discussed and correlated. [ABSTRACT FROM AUTHOR]

Conductivity and structural relaxation has been explored from modulus and dielectric loss formalisms respectively for a series of polymer composite electrolytes with zirconia as filler. The temperature dependence of conductivity followed Vogel-Tamman-Fulcher (VTF) behavior, which suggested a close correlation between conductivity and the segmental relaxation process in polymer electrolytes. Vogel temperature (T0) plays significant role in ion conduction process in these kind of materials. [ABSTRACT FROM AUTHOR]

Ba1-xCax Zr0.52Ti0.48 O3 ceramics was prepared by sol gel method. The crystallite size was in nano scale range. The dielectric constant was increased with increase in Ca2+ concentration in the sample. The dielectric loss was decreased with increase in ca concentration in the sample. The ac conductivity of the sample was increased with increase in Ca2+ concentration in the sample. The ac conductivity of the sample follows Johnscher power law. AC conductivity analysis shows that the interactions between neighbouring dipoles were decreased with the increase in Ca2+ concentration in the sample. [ABSTRACT FROM AUTHOR]

Frequency dependent dielectric measurements are carried out at several temperatures for BiFe0.98Co0.02O3. A diffuse dielectric anomaly with strong frequency dispersion has been seen ~ 400K- 600K. The temperature corresponding to the maximum of the peak satisfies the Vogel- Fulcher relation and other characteristics of a relaxor ferroelectric. Havrliak- Negami equation equivalent for impedance is found to be well fitting the Cole-Cole plot. The relaxation time obtained from the fitting shows slower dynamics at higher temperatures. [ABSTRACT FROM AUTHOR]

The CaCu3Ti4O12 (CCTO) remains as the best material for practical applications due to its high dielectric constant. To improve further the dielectric properties of CCTO to several orders in magnitude, a novel approach is adopted by codoping of Sr, Sb ions. The ceramic samples were fabricated by the conventional solid state route. The structure, morphology and detail dielectric properties were investigated systematically. All the samples crystalizes in a cubic symmetry with Im-3 space group. Sr substituted in Ca site can effectively suppress the grain growth, achieving a fine grained ceramic structure; however the grain size decreased slightly as Sb concentration increased further; whereas the dielectric permittivity of the ceramics increased drastically. The giant dielectric response was considered to be closely related with a reduction in the potential barrier height at grain boundaries (GBs) supported by the reduction in the activation energy for the conduction process. [ABSTRACT FROM AUTHOR]

Physical properties are known to be drastically varied with crystallite size and in a multifunctional material this size reduction is seem to be interesting. One such material is chosen as LaFeO3 nanoparticles which have been prepared by wet-chemical route. The average particle size found to be in the order of 45nm in which the chemical content of the unit cell has been verified. A distorted orthorhombic structure with Pbnm space group is possessed by this nanoparticle. From the bifurcation of ZFC and FC in low field, behavior of inverse susceptibility and the small hysteresis loop favors the material to be in a weak FM state well below the Neel temperature. The electrical behavior and the conduction mechanism above room temperature have been studied by cole-cole plot of the Impedance spectra. The high frequency depressed semi circles represent the grain conduction while the intermediate frequency semi circles appear may be due to grain boundary effect. [ABSTRACT FROM AUTHOR]

Nanostructured Bi2O3 was prepared through mechanical alloying method. Detailed microstructural information was obtained after Rietveld refinement of the prepared samples. The Transmission Electron Microscope images confirmed the crystallinity of the sample. The average crystallite size decreases whereas microstrain increases due to milling. The ionic conductivity of the milled sample was found to have increased few orders than the unmilled sample. The change in structural and electrical properties due to milling were discussed and correlated. [ABSTRACT FROM AUTHOR]

Frequency dependent dielectric measurements are carried out at several temperatures for BiFe0.98Co0.02O3. A diffuse dielectric anomaly with strong frequency dispersion has been seen ~ 400K- 600K. The temperature corresponding to the maximum of the peak satisfies the Vogel- Fulcher relation and other characteristics of a relaxor ferroelectric. Havrliak- Negami equation equivalent for impedance is found to be well fitting the Cole-Cole plot. The relaxation time obtained from the fitting shows slower dynamics at higher temperatures. [ABSTRACT FROM AUTHOR]