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This paper describes the processing, microstructure, optical and electrical properties of the nanocrystalline (NC) niobium and zinc doped titanium-tin-oxide (TTO:NZ) based ceramics. Variety of techniques was employed (X-ray diffraction, scanning electron microscopy, energy dispersive, Raman and impedance spectroscopy) in the characterization of the obtained TTO:NZ, which confirmed the formation of NC solid-solution matrix with Ti0.8Sn0.2O2 composition. A specific highly dense (approximately 97% of the theoretical density was reached) varistor like microstructure (matrix metal-oxide grains surrounded by the grain-boundary regions) and accordingly resembling electrical properties (breakdown electric field of approximately 130 V/mm and nonlinearity coefficient of α ≈ 6.5) were achieved through double cation doping and elected condition of the mechanochemical solid-state synthesis. Impedance response analysis of TTO:NZ ceramics by means of an equivalent electrical circuit based on the brick-layer model for polycrystalline materials revealed the presence of two temperature dependent electrical relaxation phenomena of the non-Debye type as well as the negative temperature coefficient of resistance behavior.

In this research we prepared nanocrystalline YNbO4:Eu3+ phosphor, i.e. nanophosphor, powder using an efficient mechanochemical method followed by annealing. X-ray diffraction analysis revealed that YNbO4:Eu3+ crystallizes in monoclinic structure C2/c where, from the point of view of A and B in ABO(4) compounds, cation coordination can be noted as [6+2, 4+2]. Crystallite size of about 40 nm, was estimated using Debye Scherrers equation. Raman spectroscopy with 785 and 532 rim excitation wavelengths is performed to record a majority of materials phonon modes and to provide more in depth understanding of the YNbO4 structure. Scanning electron microscopy observations indicate that the mechanical treatment during synthesis is causing non-uniformity of the powder microstructure. High resolution photoluminescent measurements upon UV excitation showed intense emission coming from f-f transitions of the europium ion with the lifetime of 0.68 ms, suggesting that the obtained YNbO4:Eu3+ is a good potential phosphor. A comparison of emissive properties with microcrystalline YNbO4:Eu3+ was made and it showed higher values of emission intensity and lifetime of the nanocrystalline sample.(C) 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

In this research we prepared nanocrystalline YNbO4:Eu3+ phosphor, i.e. nanophosphor, powder using an efficient mechanochemical method followed by annealing. X-ray diffraction analysis revealed that YNbO4:Eu3+ crystallizes in monoclinic structure C2/c where, from the point of view of A and B in ABO(4) compounds, cation coordination can be noted as [6+2, 4+2]. Crystallite size of about 40 nm, was estimated using Debye Scherrers equation. Raman spectroscopy with 785 and 532 rim excitation wavelengths is performed to record a majority of materials phonon modes and to provide more in depth understanding of the YNbO4 structure. Scanning electron microscopy observations indicate that the mechanical treatment during synthesis is causing non-uniformity of the powder microstructure. High resolution photoluminescent measurements upon UV excitation showed intense emission coming from f-f transitions of the europium ion with the lifetime of 0.68 ms, suggesting that the obtained YNbO4:Eu3+ is a good potential phosphor. A comparison of emissive properties with microcrystalline YNbO4:Eu3+ was made and it showed higher values of emission intensity and lifetime of the nanocrystalline sample.(C) 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved.