S.K. Arora

Gel growth of single crystals of barium and strontium tungstates

Abstract An account of the growth of single crystals of the tungstates of barium and strontium in gels has been presented. While “impure” gel has been found to produce three-dimensional spherulites, good quality single crystals have been obtained by using “pure” gel. Some aspects, such as (i) crystallization apparatus, (ii) effect of pH value, temperature, and concentration changes in reactants, have been studied and described. A simple procedure to contrl nucleation sites in gels has been adopted, which has resulted into a dramatic increase in the size of the crystals.

Electrochemical characteristics of copper tungstate single crystals

Fabrication and characterisation of photoelectrochemical solar cells employing flux-grown copper tungstate single crystals have been accomplished. Mott-Schottky plots have been drawn to provide a useful estimation of the properties of CuWO4 from the measurements, and thus the nature and the values of the parameters ND, EC, EF and EV of the semiconductor have been determined. The J-V characteristics of the crystal in contact with KCl/H2SO4 electrolyte are discussed with reference to the charge transfer mechanism operative at the interface.

Growth of strontium tartrate tetrahydrate single crystals in silica gels

Growth of single crystals of strontium tartrate tetrahydrate by controlled diffusion in silica gels has been narrated. In the field of material science, there is always a keen and competitive race to grow perfect single crystals with sufficient purity and perfection. Successful attempts to larger as well as more perfect crystals of SrTr are described in this paper and thus probably the largest (about 2 in. across) ever grown size of gel-grown products is reported here. The effect of several parameters, e.g. crystallization apparatus, environmental temperature, reactant concentration, gel density, gel-ageing and gel pH, on the size, quality and morphology of the crystals has also been studied.

Growth and important properties of CuWO4 single crystals

Abstract CuWO 4 single crystals were grown from slow-cooled indirect flux reaction technique. The grown crystals were characterized using EDAX, X-ray diffraction, IR, etc.

Controlled nucleation of cadmium oxalate in silica hydrogel and characterization of grown crystals

Abstract Cadmium oxalate trihydrate single crystals have been grown in silica hydrogel at ambient temperatures employing various nucleation control methods. Conventional methods such as concentration programming, two-gel technique, seeding, gel ageing, etc., were less successful in reducing nucleation centres than the addition of foreign substances such as LiCl, NaCl, KCl and NH4Cl, added to modify the initial characteristics of the gel. They helped to suppress dramatically the density of nucleation centres. Crystals grown in silica gels with NH4Cl addition were flawless and up to about 22 times larger than the ones obtained with conventional methods. Chemical etching proved a high degree of perfection of the crystals. The crystals were characterized by thermogravimetric analysis, mechanical strength measurements and dissolution behaviour.

Growth of mixed Sr1−xCaxC4H4O6 crystals in gel

Abstract Mixed crystals of strontium-calcium tartrates of different configurations have been grown for the first time in silica gels. Growth in a more convenient and simple apparatus has been accomplished and described here. Suitable chemical and X-ray diffraction methods have been employed for the characterization of grown crystals.

Optical characterization of CuWO4 single crystals

Abstract The optical absorption in single crystals of CuWO4 has been studied at room temperature in the wavelength range 300–2000 nm. Crystalline samples suitable for optical measurements were prepared by the flux method. Optical absorption studies indicate a shoulder in the absorption edge akin to the transition from the valence to the conduction band.

Crystal growth of BaWO4 and SrWO4 by flux evaporation

An account is presented of the growth of large and high quality single crystals of barium and strontium tungstates by evaporating their respective solutions in molten NaCl-LiCl system. A study of the relation of crystal morphology to growth temperature has also been made. Perfect cleavages of the grown crystals have been found and interferometrically examined. Crystalline perfection has been studied using the chemical etch-pit method. Microtopographical investigations carried out on the as-grown faces have revealed a mechanism of crystal growth. At times, large inclusions which introduce stresses in the crystals are responsible for a large dislocation concentration.

Large step-height spirals on BaMoO4 crystals

The single crystalline platelets of barium molybdate were grown from a LiCl solvent using the method of isothermal flux evaporation at 700°C. The floating platelets exhibited a spirally depressed pattern on their top as grown surface. The nature and the probable mechanism of their formation is explained as a manifestation of lamellar growth.

Growth of single crystals of barium tungstate by double decomposition in melt

The suitability of double decomposition reaction in molten phase for the growth of good quality single crystals of barium tungstate, an isotype of scheelite, has been investigation. The crystals grown have been identified by X-ray analysis. The crystals are quite transparant with flat, smooth and well-developed {111} habit faces. Studies made on chemical etching of the cleavages have revealed that the crystals are relatively perfect. A major source of dislocations has been conjectured to be the inclusions present in the crystals.