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Glass samples with general formula NaCo1−x (VO) x PO4 (x = 0.1, 0.3, 0.5 and 0.7) are synthesized via a simple melt quenching method followed by high-energy ball milling for 30 h to form the homogeneous nanoscaled glass powders. DTA traces of all the glass and glass–ceramic samples indicated exothermic processes confirming selective crystallization induced in the glass network. The formation of major crystalline phase [sodium cobalt pyrophosphate (Na2CoP2O7)] with an ordered layered structure was monitored by X-ray diffraction and the same was justified by SEM images. Structural illustration of major crystalline Na2CoP2O7 phase offered more intra-layer Co–Co distance (7.12 A) than inter-layer Co–Co distance (5.37 A) which facilitates two-dimensional Na-ion diffusion pathways to achieve the fast intercalation and de-intercalation phenomenon along the a and c directions. The ionic conductivity was monitored by Impedance analysis and achieved to be highest (6.41 × 10−7 S cm−1) for the glass–ceramic cathode x = 0.3, NaCo1−x (VO) x PO4. The initial discharge capacity for the highest conducting NaCo0.7(VO)0.3PO4 cathode is obtained as 93 mA h g−1 in 0.1 C and had 65% capacity retention even at high rate 10 C.

The role of La+3/Sr+2 ratios, which is varied from 0.08 to 5.09, on density, molar volume, packing fraction, free volume, thermal and electrical properties in strontium lanthanum aluminoborosilicate based glass sealants intended for solid oxide fuel cell (SOFC) applications is evaluated. The studies reveal expansion of the glass network evident from increasing molar volume and decreasing packing fraction of glasses with progressive La+3 substitutions. The molecular origin of these macroscopic structural features can be accounted for by the free volume parameters measured from positron annihilation lifetime spectroscopy (PALS). The La+3 induced expanded glass networks show increased number of subnanoscopic voids with larger sizes, as revealed from the ortho-positronium (o-Ps) lifetime and its intensity. A remarkably direct correspondence between the molar volume and fractional free volume trend is established with progressive La2O3 substitution in the glasses. The effect of these structural changes on the glass transition temperature, softening temperature, coefficient of thermal expansion, thermal stability as well as electrical conductivity has been studied.

Citrate-nitrate autocombustion process is a promising synthesis route in the field of nanomaterials. This route involves many controlling parameters which ultimately affect properties of the products. In the present research work, the effect of concentration of fuel to that of metal nitrates has been studied in a systematic manner. The nature of exothermic reaction was analyzed with DSC-TGA and the powder properties were characterized by XRD, TEM and BET measurement. The properties of the powders have been explained with respect to fuel content, vigorousness of the exothermic reaction, combustion temperature and duration. The most vigorous reaction was found to occur for the composition with FER of 0.50 with the production of the smallest crystallite size of 9 nm.

Nanocrystalline yttrium aluminium garnet (YAG) powder has been synthesised by sucrose combustion method. A foamy mass obtained by drying a resin prepared by heating yttrium nitrate, aluminium nitrate and sucrose undergoes self-sustained combustion when initiated with a burning splinter and produces YAG precursors containing amorphous oxides of yttrium and aluminium. The YAG phase has been obtained from the precursors during calcination at a relatively low temperature of 900°C without the formation of any intermediate compounds. The YAG powder prepared by planetary ball milling of the combustion product calcined at 900°C contained particles in the size range of 0·06 to 5 μm with a D 50 value of 1·04 μm and had a surface area of 21·5 m2 g−1. The YAG particles are aggregate of crystallites of the size nearly 30 nm.

Nanocrystalline yittria-stabilized zirconia (YSZ) compounds with yittria concentration varying between 8 and 12 mol% have been synthesized by gel combustion method followed by heat treatment at 550°C. The YSZs are found to posses stable face centered cubic structure at room temperature by X-ray diffractometry. The lattice parameter ‘a’ showed an increasing trend with increasing concentration of yittria. The crystallite size estimated by Scherrer method was in the range of 7–10 nm. Band gap studies showed an increasing trend with increasing yittria concentration and are found to be consistent with respective lattice parameters following the tight binding approximation or linear combination of atomic orbitals approximation.

A series of SOFC glass sealants with composition SrO (x), La(2)O(3) (15), Al(2)O(3) (15), B(2)O(3) (40 - x), and SiO(2) (30) [x = 10, 15, 20, 25 and 30] (wt.%) [SLABS] are investigated for their structure property correlations at different compositions. Quantitative Fourier transform infrared spectroscopy shows structural rigidity with increasing SrO content, as demonstrate by an increase in the Si-O-Si/O-Si-O bending and B-O-B stretching frequencies. The role of SrO as a modifier dominates the control of the structure and behaviour of glasses compared with the effect of network formers, i.e., the B(2)O(3)/SiO(2) ratio. Consequent to the structural changes, increasing substitution of B(2)O(3) by SrO the glasses causes increases in the density, glass transition temperature and dilatometric softening point. On the other hand, the crystallization temperatures show a decreasing trend and the coefficient of thermal expansion increases with increase in substitution. (C) 2011 Elsevier B.V. All rights reserved.

Nanocrystalline 8 mol% yttria stabilized zirconia (YSZ) powder was synthesized using polyvinyl alcohol (PVA) as organic precursor and acidic solutions of yttrium oxynitrite and zirconium nitrate. Complex formation was established using Fourier transform infrared (FTIR) spectroscopy and solid state (13)C nuclear magnetic resonance (NMR) spectroscopy. Thermal stability of the complex was investigated by thermogravimetric analysis (TGA). X-ray diffractometry (XRD) revealed formation of cubic phase YSZ at a temperature as low as 600 degrees C. The lattice parameter and average crystallite size were calculated from the XRD data. Particle size of the YSZ powder was investigated through transmission electron microscopy (TEM). The band gap of the sintered YSZ pellet was measured by UV-Vis-diffused reflectance spectroscopy (DRS). AC electrical conductivity was measured in air at 1 kHz frequency using a programmable RCL meter. The activation energy was calculated from the conductivity data at different temperatures using the standard Arrhenius equation. (C) 2009 Elsevier Ltd and Techna Group S.r.l. .