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Synthesis, Characterization, Optical and Transport Properties of BaSnO3Synthesized by Wet Chemical Route

Materials Sciences and Applications 2018年第1期9卷 92-110页

作者： Rakesh Kurre Sharmila bajpai parmendra kumar bajpai Department of Pure & Applied Physics Guru Ghasidas Vishwavidyalaya Bilaspur India

Alkaline earth stannates have renewed attention as potential materials for gas sensing, transparent conducting oxides and ceramic capacitor applications. A noble wet chemical route is chosen to synthesize BaSnO3 powders having micron size grains. Problems related to uneven grains and poor densification in conventional solid state route have been overcome in the present method. X-ray diffraction data confirms the single phase formation without any secondary phase having cubic perovskite structure (S.G. Pm-3m). The estimated lattice parameter is ≈4.11933Åand percentage density is ≈90%. The microstructure probed by scanning electron micrograph reveals almost homogeneously distributed particles having random shape with some porosity. Phonon modes in FT-IR and Raman spectra confirm the local symmetry distortion. The DC conductivity at 200°C approaches almost 2 × 10-2 (Ω-cm)-1, which is almost of the same order as that observed in perovskite based electronic conductors. DC and a.c. electrical conductivity of the material follow Mott’s variable range hopping at low temperature and Arrhenius type thermally activated process at elevated temperatures. Evidence of small polar on formation is also verified. Optical band gap estimated from absorption data is ≈2.94 very close to the reported value. Composition prepared through the noble wet chemical route has high electrical conduction and suitable for gas sensing applications.

关键词： X-Ray Diffraction Raman Spectra Variable Range Hopping Phonons

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Effect of Substrate on CuS/PVA Nanocomposite Thin Films Deposited on Glass and Silicon Substrate

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Soft Nanoscience Letters 2018年第2期8卷 9-19页

作者： Sandhya Yadav parmendra kumar bajpai Advance Materials Research Laboratory Department of Pure & Applied Physics Guru Ghasidas Vishwavidyalaya Bilaspur India

Transition metal chalcogenide nanocomposite thin films deposited by chemical routes are currently attracting wide attention being inexpensive, simple and have utility for large area applications. The role of substrate becomes very important in film deposition as well as in controlling their properties due to strain induced properties modification and lattice mismatch. CuS/PVA nanocomposite thin films were successfully deposited on glass and silicon substrates using sol-gel technique. Thin films were characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), UV-visible (UV-VIS) and Raman spectroscopy. Structural data confirm the amorphous nature of as grown films which transform into crystalline films after annealing at 200°C. The degree of crystallinity seems to be better in film deposited on silicon substrate in comparison to those grown over glass substrate with average crystallite sizes ≅?4.00 nm and 7.00 nm for films deposited on glass and silicon substrate respectively. Atomic force microscopy (AFM) images in dynamic as well as contact modes display nanoparticles embedded in polymer network. The films surface roughness parameters quantitatively estimated from AFM micrographs are compared. Raman spectra show a sharp peak at ≅474 cm¯1 assigned to S-S stretching mode of S2 ions in films grown on both substrates and associated as due to presence of hexagonal (covellite) crystal structure. Optical band gaps of thin film on glass and silicon substrate are 2.10 eV and 2.02 eV respectively. The effect of substrate on the measured properties is discussed.

关键词： Copper Sulfide Nanocomposite Thin Films Surface Morphology Optical Band Gap Atomic Force Microscopy Raman Spectra

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Dielectric Relaxation in Pure Columbite Phase of SrNb2O6Ceramic Material: Impedance Analysis

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World Journal of Condensed Matter Physics 2011年第2期1卷 37-48页

作者： Karuna Nidhan Singh parmendra kumar bajpai 不详

Controlling the heating rate during calcination and cooling rate during sintering, pure columbite like phase of SrNb2O6 is synthesized. By optimizing the sintering temperature, ceramic with density (>92%) is achieved for material calcined at 11250C and sintered at 12000C. The ceramic shows orthorhombic structure with lattice parameters a = 11.011 ? b = 7.7136 ?, c = 5.5969? having average grain size ≈ 1.03 μm. The temperature dependent dielectric response shows a peak at temperature 300.90C, which shows significant dielectric dispersion towards high temperature side of the peak with almost dispersion free low temperature side;an effect observed in relaxors. Dielectric dispersion in the material is fitted with the Jonscher’s relation. Impedance analysis suggests strongly temperature dependent relaxation. The dielectric relaxation is polydispersive and conduction is mainly through grains. The equivalent circuit model for the impedance response is proposed and the temperature dependence of circuit elements deduced. The frequency dependent ac conductivity at different temperatures indicated that the conduction is governed through thermally activated processes. AC conduction activation energies are estimated from Arrhenius plots and conduction mechanism is discussed.

关键词： Electro Ceramics Dielectrics Microstructure Sintering Optimization Dielectric Relaxation

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Conclusive Growth of CdTe Nanorods by Solvothermal Decomposition Using Single Source Precursors

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Soft Nanoscience Letters 2013年第3期3卷 52-57页

作者： Arunendera kumar Tiwari Vinay kumar Verma Tripti A. Jain parmendra kumar bajpai Department of Pure and Applied Physics Guru Ghasidas Vishwavidyalaya Bilaspur India Department RTDC Sharda University Greater Noida India Disha Institute of Management and Technology Raipur India

CdTe nanorods are synthesized by solvothermal decomposition, using single source molecular precursors (SSMP) cadmium (II), complex of bis-(aminopropyl telluride) (SSMP-I) and cadmium (II) bis-(isopropyl telluro) propane (SSMP-II) and quinoline as solvent at relatively low temperature (210°C). As synthesized nanomaterials are structurally characterized by XRD and SEM, SEM micrographs revealed formation of rod shapes structures whose dimensions change with the source precursor molecule. The average crystallite size estimated from XRD data is 29.78 and 28.94 nm respectively using Precursors I and II. The average size of nanorods is 1.237 μm and 0.15μm respectively, estimated from SEM micrographs. These are much larger than the average crystallite size estimated from XRD data. This is attributed to the agglomeration of nanocrystallites as quinoline is not a good capping agent.

关键词： Single Source Molecular Precursor CdTe Nanorods SEM Solvothermal Synthesis

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