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The synthesis of nanocrystalline calcium molybdate (CaMoO 4 ) through an autoigniting combustion technique is reported in this paper. The structural characterization of the as-prepared nanocrystallites were done by X-ray diffraction (XRD), Fourier transform Raman, and Fourier transform infrared (IR) spectroscopy and the morphological studies using transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The studies reveal that the as-prepared powder itself was phase pure with tetragonal structure and of particle size 25 nm. The sample was sintered at a relatively low temperature of 775 8C to a high density of $95% for the first time, without the use of any sintering aid. The optical bandgap energy calculated from the ultraviolet-visible absorption spectrum for the as-prepared and annealed sample was 3.72 and 3.99 eV, respectively. The photoluminescence spectra of the sample showed an intense emission in the green region (528 nm). The dielectric constant and loss factor of the sample at 5 MHz was found to be 11.00 and 6.40 Â 10 À3 at room temperature. The temperature coefficient of dielectric constant was À95.04 pp/8C. These observations reveal that nanostructured CaMoO 4 is a promising scheelite low-temperature co-fired ceramic (LTCC) and also an excellent luminescent material.

Synthesis of nano-BaWO4by a modified combustion technique and its suitability for various applications are reported. The structure and phase purity of the sample analyzed by X-ray diffraction, Fourier transform Raman, and infrared spectroscopy show that the sample is phase pure with tetragonal structure. The particle size from the transmission electron microscopy is 22 nm. The basic optical properties and optical constants of the nano BaWO4are studied using UV-visible absorption spectroscopy which showed that the material is a wide band gap semiconductor with band gap of 4.1 eV. The sample shows poor transmittance in ultraviolet region while maximum in visible-near infrared regions. The photoluminescence spectra show intense emission in blue region. The sample is sintered at low temperature of 810°C, without any sintering aid. Surface morphology of the sample is analyzed by scanning electron microscopy. The dielectric constant and loss factor measured at 5 MHz are 9 and1.56×10-3. The temperature coefficient of dielectric constant is −22 ppm/°C. The experimental results obtained in the present work claim the potential use of nano BaWO4as UV filters, transparent films for window layers on solar cells, antireflection coatings, scintillators, detectors, and for LTCC applications.

Single crystals of ammonium D, L-tartrate, a potential nonlinear optical (NLO) material of interest, were grown by the slow evaporation technique. The crystal structure was determined by single-crystal X-ray diffraction. Fourier transform infrared and Raman spectra of the crystallized molecule were recorded and analyzed. The geometry, intermolecular hydrogen bonding, first hyperpolarizability and harmonic vibrational wavenumbers were calculated with the help of B3LYP density functional theory method. The red shift of hydroxyl and NH 4 + stretching wavenumbers indicate the formation of inter-and intramolecular hydrogen bonding. Simultaneous activation of CH stretching wavenumbers shows the presence of intramolecular charge transfer in the molecule. Natural bond orbital analysis was carried out to demonstrate the various inter-and intramolecular interactions that are responsible for the stabilization of this molecule, leading to high NLO activity.

a b s t r a c tThe optical properties of nanocrystalline HfO 2 synthesized using a single-step auto-igniting combustion technique is reported. Nanocrystalline hafnium oxide having particle size of the order 10-15 nm were obtained in the present method. The nanopowder was characterized using X-ray diffraction, Fourier transform infrared and Fourier transform Raman spectroscopic studies. All these studies confirm that the phase formation is complete in the combustion synthesis and monoclinic phase [P2 1 /c (14)] of HfO 2 is obtained without the presence of any impurities or additional phases. The powder morphology of the as-prepared sample was studied using transmission electron microscopy and the results were in good agreement with that of the X-ray diffraction studies. The optical constants such as refractive index, extinction coefficient, optical conductivity and the band gap were estimated from UV-vis spectroscopic techniques. The band gap of nanocrystalline HfO 2 was found to be 5.1 eV and the sample shows a broad PL emission at 628 nm. It is concluded that the transitions between intermediate energy levels in the band gap are responsible for the interesting photoluminescent properties of nanocrystalline HfO 2 .