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Aliovalent anion substitution in inorganic materials brings about marked changes in properties, as exemplified by N,F‐codoped metal oxides. Recently, complete substitution of oxygen in ZnO by N and F was carried out to generate Zn 2 NF. In view of the important properties of TiO 2 , we have attempted to prepare TiNF by employing an entirely new procedure involving the reaction of TiN with TiF 4 . While the reaction at low temperature (450 °C) yields TiNF in the anatase phase, reaction at a higher temperature (600 °C) yields TiNF in the rutile phase. This is interesting since the anatase phase of TiO 2 also transforms to the rutile phase on heating. The lattice parameters of TiNF are close to those of the parent oxide. Partial substitution of oxygen in TiO 2 by N and F reduces the band gap, but complete substitution increases the value comparable to that of the oxide. We have examined properties of N,F‐codoped TiO 2 , and more interestingly N,F‐codoped Ti 3 O 5 , both with lower band gaps than the parent oxides. A detailed first‐principles calculations has been carried out on structural and electronic properties of N,F−TiO 2 and the TiNF phases. This has enabled us to understand the effects of N,F substitution in TiO 2 in terms of the crystal structure, electronic structure and optical properties.

Systematics in the superconducting behaviour of Ln 2−xSr x(Ba x)CuO 4, La 2−xSr x−yBa y(Ca y)CuO 4, (La 1−xLn x) 2−ySr y(Ba y)CuO 4 with Ln = Pr, Nd or Y and related systems are presented. The role of oxygen stoichiometry and lattice parameters of these mixed valent copper oxides is indicated. These high T c superconducting oxides exhibit high-temperature resistivities in the borderline of the metal-nonmetal transition.

Metastable phases of Ga1-x Al x FeO3 (x = 0, 0.25, 0.5) have been prepared under high pressure (4.5 GPa) and high temperature (1000 °C) using a cubic-anvil high pressure apparatus. X-ray diffraction studies show that application of pressure transforms the structure of these compounds from the polar Pna21 to the non-polar R 3 ̅ c phase. Intriguingly, the orthorhombic phase of the compound with x = 1.0, synthesized at ambient pressure decomposes into their constituent oxides, Al2O3 (R 3 ̅ c) and Fe2O3 (R 3 ̅ c) under the same conditions of pressure and temperature. Magnetization measurements reveal antiferromagnetic ordering with a weak ferromagnetism below T N ~ 450 K, 590 K and 650 K, respectively. All these oxides exhibit a spin glass behavior at low temperatures. Analysis of ac susceptibility measurements indicate the existence of a cluster spin glass phase below T * ~ 45, 40 and 43 K respectively for x = 0, 0.25, 0.5. Such a re-entrant spin glass behavior arises due to antiferromagnetic interactions among the disordered Fe3+ ions in the octahedral site of the corundum structure.

Several methods have been employed to synthesize SiC nanowires. The methods include heating silica gel or fumed silica with activated carbon in a reducing atmosphere, the carbon particles being produced in situ in one of the methods. The simplest method to obtain β-SiC nanowires involves heating silica gel with activated carbon at 1360 °C in H2 or NH3. The same reaction, if carried out in the presence of catalytic iron particles, at 1200 °C gives α-Si3N4 nanowires and Si2N2O nanowires at 1100 °C. Another method to obtain Si3N4 nanowires is to heat multi-walled carbon nanotubes with silica gel at 1360 °C in an atmosphere of NH3. In the presence of catalytic Fe particles, this method yields α-Si3N4 nanowires in pure form.

A copper-binding complex formed in the exopolysaccharide fraction of Pseudomonas Aeruqinosa was isolated and characterized using a variety of techniques. By comparison with model Cu(II) complexes of uronic acids, it is shown that the Pseudonomonas Aeruginosa forms a square-planer, cupric complex similar to cupric glucuronates.

Arsenic selenide-telluride glasses have been investigated by X-ray absorption and photoelectron spectroscopy. The core electron energy shifts and chemical shifts in K-absorption edge measurements associated with the glass-crystal transitions of pure As2Se3 and As2Te3 have been studied. The effect of composition on the core level energy and valence bands of As2(Se,Te)3 glasses, has been discussed. Mixed-composition glasses are found to be considerably ionic.