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Background: Zinc oxide (ZnO) is one of the most attractive II-VI semiconductor oxide material, because of its direct wide band gap (3.37 eV) and large binding energy (60 meV). Zinc oxide (ZnO) is a promising semiconductor due to its optimised optical properties. Among semiconductor nanostructures, the vertically aligned one-dimensional ZnO nanorods are very important for nano device application. Methods: Vertically aligned ZnO nanorod arrays were grown on ZnO, aluminum doped ZnO (ZnO:Al), tantalum doped ZnO (ZnO:Ta) and aluminum and tantalum co-doped ZnO (ZnO:Al,Ta) seed layer by hydrothermal method. Results: The X-Ray Diffraction (XRD) investigation indicated the presence of hexagonal phase for the both seed layers and nanorods. The Scanning Electron Microscope (SEM) images of ZnO and doped ZnO seed layer thin-films show spherical shaped nanograins organized into wave like morphology. The optical absorption spectra revealed shift in absorption edge towards the shorter wavelength (blue shifted) for ZnO nanorods grown on ZnO:Al, ZnO:Ta and ZnO:Al,Ta seed layer compared to ZnO nanorods grown on ZnO seed layer. Conclusion: The increase in band gap value for the ZnO nanorods grown on doped ZnO seed layers due to the decrease in crystallite size and lattice constant as evidenced from XRD analysis. The unique property of Al, Ta doped ZnO can be used to fabricate nano-optoelectronic devices and photovoltaic devices, due to their improved optical properties.

Theoretical calculations are performed to investigate the electronic structure, structural phase stability and optical properties of double perovskite oxide semiconductors namely Sr2AMoO6 (A= Mg, Zn) in tetragonal symmetry using WIEN2k. In order to estimate the ground state parameters, total energies are calculated with respect to molecular volume and the energies are fitted with Brich – Murnaghan equation of state. The estimated ground state parameters are comparable with the available experimental data. The band structure calculations for these compounds reveal that these compounds exhibit semiconducting behaviour with an indirect band gap. To explore the optical transitions in these compounds, the real and imaginary parts of the dielectric function are analyzed at ambient conditions and the important optical constants are calculated.

First principle calculations based on density functional theory have been performed to investigate the structural stability, electronic structure and Li+ intercalation potential for the compounds LiM2Sn (M= Cd,Zn,Pd). These electrode materials exhibit small percentage of volume change which accounts for excellent structural stability. The computed band structure along high symmetry lines in the Brillion zone, total and partial density of states clearly reveals that insertion of lithium to these electrode materials does not affect their metallic nature. The valence charge density calculation reveals the dominant ionic character of these compounds enables Li+ accommodation.

First principle calculations are performed to investigate the electronic structure, structural phase stability, optical properties and thermoelectric properties of double perovskite oxide semiconductors namely Sr 2 AlM'O 6 (M' = Nb and Ta) in the cubic symmetry using WIEN2k. In order to study the ground state properties of these compounds, the total energies are calculated as a function of reduced volumes and fitted with Brich Murnaghan equation. The estimated ground state parameters are comparable with the available experimental data. Calculations of electronic band structure on these compounds have been carried out using generalized gradient approximations and modified Becke-Johanson potential (TB-mBJ). The calculated band gap for Sr 2 AlNbO 6 and Sr 2 AlTaO 6 with GGA and TB-mBJ reveal that these compounds exhibit semiconducting behavior with a direct band gap. To explore the optical transitions in these compounds, the real and imaginary parts of the dielectric function, refractive index, extinction coefficient, reflectivity, optical absorption coefficient, real part of optical conductivity and the energy-loss function are calculated at ambient conditions and analyzed both with GGA and TB-mBJ potentials. Investigations of the thermoelectric properties of these compounds have been carried out by the calculations of transport coefficients based on Boltzmann transport theory in order to analyze the variation of Seebeck's coefficient at different temperatures for various carrier concentrations based on the electronic structure near the valence band maxima.

First-principle calculations based on density functional theory have been performed to investigate the negative electrode behaviors, structural changes, and electronic and bonding properties of lithium intercalated antimonides Ag3Sb and Mg3Sb2. Initial intercalation of lithium to orthorhombic Ag3Sb led to form cubic Li2AgSb. Lithium insertion to hexagonal Mg3Sb2 results in cubic LiMgSb. Further insertion of lithium with the intercalated compounds Li2AgSb and LiMgSb results in to the formation of alkali antimonide Li3Sb. The structural transformation of both antimonides Ag3Sb and Mg3Sb2 followed by the insertion of Li+ ends with the formation of Li3Sb with cubic phase. The computed band structures along high symmetry directions of the Brillouin zone, and total and partial density of states clearly illustrate that the intercalation of lithium with Ag3Sb and Mg3Sb2 changes their metallic nature into semiconductor. From the charge density calculations, it is observed that the covalent bond nature in the parent phases Ag3Sb and Mg3Sb2 changed into ionic bond in the Li+ intercalated phases Li2AgSb, LiMgSb, and Li3Sb.

First principle calculations based on density functional theory have been performed on lithium containing transition metal sulfides Li2TiS3 and Li3NbS4 which are recently identified as novel positive electrode materials for rechargeable Li+ batteries. The calculations were performed to investigate the structural stability, electronic and transport properties of Li2TiS3 and Li3NbS4 along with their corresponding delithiated phases LiTiS3 and Li2NbS4. In this study it has been observed that these lithium containing sulfur materials maintain their face-centered cubic structure upon extraction of Li+. To calculate the structural stability and volume change due to lithium extraction, the total energies of Li2TiS3, Li3NbS4 and their corresponding delithiated phases LiTiS3 and Li2NbS4 have been computed by applying full potential linearized augmented plane wave (FP-LAPW) method implemented in WIEN2K. The equilibrium structural parameters for all the phases were determined by achieving total energy convergence. These electrode materials exhibit very small percentage of volume change with change in Li+ concentration which accounts for excellent structural stability. The computed band structure along high symmetry lines in the Brillouin zone, total and partial density of states clearly reveals that the extraction lithium from these electrode materials does not change their metallic nature. The electronic conductivities of both lithiated and delithiated phases have been calculated by employing BoltzTrap which can be interfaced with WIEN2K. The topological distributions of electron charge density at various critical points within the system were analyzed with the use of CRITIC code which is based on Bader’s theory of atoms in molecules (AIM). From the charge density calculations, it was observed that, there is strong ionic bond and weak covalent bond between atoms of the compounds Li2TiS3 and Li3NbS4. But the ionic bond nature was found to decrease in the delithiated phases LiTiS3 and Li2NbS4. The calculated values of electronic conductivities and discharge voltages for both electrodes are found to be in accordance with the recent experimental reports.

CdS, sodium doped CdS (CdS:Na), potassium doped CdS (CdS:K) and sodium and potassium dual doped CdS (CdS:Na,K) thin films were deposited on glass substrate by chemical bath deposition (CBD) technique. Structural, morphological and optical properties of the as-grown films were characterised using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDAX), atomic force microscopy (AFM) and ultraviolet visible (UV–VIS) spectroscopy. The XRD analysis revealed cubic phase for ‘as-deposited’ CdS, CdS:Na, CdS:K and CdS:Na,K dual doped thin films. AFM analysis revealed uniform film surface with crack free and densely packed morphology for CdS:Na,K film. The absorption edge in the optical absorption spectra shifts towards the shorter wavelength for CdS:Na, CdS:K and CdS:Na,K thin films compared to CdS film. The optical band gap of CdS, CdS:Na, CdS:K and CdS:Na,K thin films was found to be 2.31, 2.35, 2.38 and 2.34 eV, respectively.

The electronic and structural properties of delafossite transparent conducting oxides, namely CuMO2 (M = Al, Ga, In), have been studied by means of self-consistent Tight Binding Linear Muffin-Tin Orbital (TB-LMTO) method. Electronic structure and hence total energies of these compounds have been computed as a function of reduced volumes and fitted with Birch Murnaghan equation. The calculated equilibrium lattice parameters and bulk modulus are in good agreement with experimental and reported values. The energy band gap of 2H (hexagonal) and 3R (trigonal) CuMO2 (M = Al, Ga, In) has been calculated and compared with available data. The stability of 2H and 3R polytypes has also been studied.

The transport phenomena in alkali-metal super ionic conductors based on Na3PO4 structure are of particular interest due to their potential technological application. Differential thermal analysis (DTA), differential scanning calorimetry (DSC), Raman spectroscopy and temperature dependent electrical conductivity measurements were carried out to probe the nature of the phase transformation involved in anhydrous Na3PO4. The changes in spectral profile of the v3 mode and the line width of v1 mode of PO 4 3− observed in the temperature interval from 331 to 345 °C revealed the high degree of disorder nature during the α-γNa3PO4 phase transformation.

The structural phase transformations of ZnS, ZnSe and ZnTe under high pressure are studied by tight binding linear muffin tin orbital (TB-LMTO) method. A simple cubic 16 (SC16) phase is observed in all three zinc chalcogenides ZnX (X=S, Se, Te) and the stability of the high pressure phases is also presented. In ZnS and ZnSe, the sequence of transformation is similar to zincblende (ZB)→SC16→rock salt (RS), but in ZnTe the transformation sequence is different, namely the SC16 phase is observed above the cinnabar phase. The ground state properties of the phases of zinc chalcogenides ZnX (X=S, Se, Te) are also calculated.

The ionic conductivity and thermo-Raman spectra of anhydrous sodium pyrophosphate Na 4 P 2 O 7 were measured dynamically in the temperature range from 25 to 600 °C with a heating rate of 2 °C min −1 to understand the structural evolution and phase transformation involved. The DSC thermogram was also measured in the same thermal process for the phase transformation investigation. The spectral variations observed in the thermo-Raman investigation indicated the transformation of Na 4 P 2 O 7 from low temperature phase ( e ) to high temperature phase ( α ) proceeded through pre-transitional region from 75 to 410 °C before the major orientational disorder at 420 °C and minor structural modifications at 511, 540 and 560 °C. The activation energies and enthalpies of the proposed phase transformations were determined. The possible mechanism for temperature dependent conductivity in Na 4 P 2 O 7 was discussed with the available data.

In this paper, detailed examination of the doping effect on electronic band structure, magnetic properties of nonmagnetic (NM) and striped antiferromagnetic (S-AFM) phases of MFeAs ( M = Li , Na ) compounds were carried out using ab initio method. The crystal structure of these compounds is a well known tetragonal structure. Self-consistent calculations were performed by plane wave pseudo potential, density functional based method using PWSCF-Quantum Espresso code. To study the structural phase stability, the total energies of these compounds were calculated as a function of reduced volumes and fitted with Brich Murnaghan equation. 3d valence elements like Mn , Co induce strong local magnetic moments on doping. However, Cu substitution weakens the average local moments. The 3d elements on doping at Fe site directly affect the electrons correlations in the Fe – As layer.

Lithium garnet Li7La3Zr2O12 (LLZ) sintered at 1230 °C has received considerable importance in recent times as result of its high total (bulk + grain boundary) ionic conductivity of 5 × 10−4 S cm−1 at room temperature. In this work we report Li+ transport process of Li7−2xLa3Zr2−xWxO12 (x = 0.3, 0.5) cubic lithium garnets. Among the investigated compounds, Li6.4La3Zr1.7W0.3O12 sintered relatively at lower temperature 1100 °C exhibits highest room temperature (30 °C) total (bulk + grain boundary) ionic conductivity of 7.89 × 10−4 S cm−1. The temperature dependencies of the bulk conductivity and relaxation frequency in the bulk are governed by the same activation energy. Scaling the conductivity spectra for both Li6.4La3Zr1.7W0.3O12 and Li6La3Zr1.5W0.5O12 sample at different temperatures merges on a single curve, which implies that the relaxation dynamics of charge carriers is independent of temperature. The shape of the imaginary part of the modulus spectra suggests that the relaxation processes are non-Debye in nature. The present studies supports the prediction of optimum Li+ concentration required for the highest room temperature Li+ conductivity in LixLa3M2O12 is around x = 6.4 ± 0.1.