Single Crystals In Silica Gels Research Articles

Morphological and FTIR Studies of Barium Oxalate Single Crystals

Abstract The conditions for the gel growth of barium oxalate single crystals in silica gels were studied in this paper. We describe the growth mechanism, effect concentration of feed solution, interchanging of the reactants, the effect of temperature and detailed study of microstructures of barium oxalate single crystals. At higher concentration of feed solution dense fibers were observed. With interchanged feed solution precipitate and spherulites have been obtained. The effect of temperature on growth barium oxalate crystals showed that there was a decrease in nucleation density at higher temperature. The crystals growth were observed under the electron microscope which revealed that the crystal have needle and spherulites structures. We also report the FTIR studies of barium oxalate crystals.

Study of growth condition and characterization of Monothiourea-Cadmium Sulphate Dihydrate single crystals in silica gel

Single crystals of Monothiourea-Cadmium Sulphate Dihydrate belonging to Semiorganic material with nonlinear optical properties have been grown in silica gel medium using gel technique. The grown crystals were subjected to single crystal X-ray diffraction (SXRD) and Fourier transform infrared spectroscopy to elucidate their lattice parameters and functional group confirmation. Vickers microhardness measurements reveal that these materials have reverse indentation size effect and belong to the category of soft materials. Further, mechanical characterizations are also asserted from yield strength and elastic stiffness studies. The dielectric studies at different temperatures and frequency applied are measured and their behavior is analyzed. Thermal behavior of the crystal was investigated by thermogravimetric analysis (TGA) and differential thermal analysis.

Optimized growth and characterization of cadmium oxalate single crystals in silica gel

Single crystals of cadmium oxalate hydrate have been grown in silica gel in the presence of divalent Cd 2+ ions impregnated with oxalic acid at room temperature. Gel aging technique was adopted to reduce the nucleation density and hence larger and more perfect single crystals were harvested. Obtained crystals exhibit triclinic structure with unit cell dimensions a = 6.0059 Å, b = 6.66 Å, c = 8.49 Å, α = 105.71°, β = 98.99° and γ = 74.66°. IR spectrum indicates the presence of oxalate ligands and water of crystallization. Thermal behavior and stability of the grown cadmium oxalate crystals were investigated in the temperature range of 30–600 °C. A.C. electrical conductivity of Cd(C 2O 4)·3H 2O was measured for different frequencies and was found to lie between usual conductivities of semiconductor and insulator. The activation energy required to move permanent intrinsic defects in the crystal lattice was found and was equal to 0.15 eV.

Study of optimum growth condition of Zinc Cadmium Thiocyanate (ZCTC) single crystals in silica gel

Some bimetallic thiocyanate complexes exhibit excellent nonlinear optical properties. Single crystals of one such material Zinc Cadmium Thiocyanate ZnCd(SCN) 4 abbreviated as ZCTC have been grown in Silica gel using gel technique by the process of diffusion. Colorless transparent crystals of size 12 mm × 2 mm × 1.3 mm have been obtained. Structural analysis has been carried out in powder form and for single crystal using X-ray diffractometer. Single crystal X-ray diffraction analysis reveals that the crystal lattice of ZCTC is tetragonal. From powder X-ray diffraction analysis the diffraction planes have been identified and unit cell parameters are determined.

Study of optimum growth condition and characterization of zinc mercury thiocyanate (ZMTC) single crystals in silica gel

Some bimetallic thiocyanate complexes exhibit excellent nonlinear optical properties. Single crystals of one such material, zinc mercury thiocyanate ZnHg(SCN) 4 have been grown in silica gel with gel technique by the process of diffusions and the optimum growth condition has been studied. Crystals of 4 mm length have been obtained. Their structural, optical and thermal properties have been studied. Structural analysis was carried out using an X-ray diffractometer and the crystal structure was confirmed to be tetragonal. Fourier transform infrared spectrum was obtained to confirm the functional groups. Transmission spectrum has been recorded in the solution state and the cut-off wavelength has been determined. Thermal stability of the grown crystal has been investigated by thermogravimetric and differential thermal analyses. Nonlinear optical property of the crystal has been confirmed using the Kurtz powder technique and a study of its second harmonic generation efficiency in comparison with urea has been made.

Effect of temperature on nucleation and growth of cadmium oxalate single crystals in silica gels

In continuation of our earlier work on the gel growth of single crystals, this paper presents results on the effect of temperature on nucleation and growth of cadmium oxalate single crystals. It has been found that the nucleation centres decrease drastically (to as low as two) as the temperature increases. Low nucleation centres resulted in larger and more perfect single crystals. The decrease in nucleation centres at higher temperature has been interpreted in terms of a decrease in supersaturation, an increase in critical size of nucleus and free energy of nucleus formation. The growth rates of the crystals measured as a function of temperature has clearly indicated that the crystal growth process in gel is a one-dimensional diffusion controlled process.

Growth of Doped Potassium Perchlorate Single Crystals in Silica Gel and Their Characterization

Chemical reaction method was employed to grow doped potassium perchlorate single crystals in silica gel. Dopants used were potassium permanganate and potassium dichromate and the dopant levels were 500 and 1000 ppm. FT-IR spectral analysis, etching study and microhardness measurements were carried out for these crystals.

Growth and characterization of pure and cadmium doped strontium tartrate tetrahydrate single crystals

The growth of pure and cadmium doped strontium tartrate tetrahydrate single crystals in silica gel is described. A systematic study of the dependence of the uptake of the dopant on the molarity of the dopant employed for the growth is presented in this paper. X-ray diffraction, Chemical etching, TGA, DSC, FTIR studies have been done and the results are reported.

Growth and characterization of pure and doped lead hydrogen phosphate single crystals in silica gel

AbstractFollowing the chemical reaction method pure and doped lead hydrogen phosphate single crystals were grown in silica gel using different gel density, various concentrations of phosphoric acid, and lead nitrate solutions. As the gel pH plays an important role in the formation of different H3PO4 species in the phosphoric acid system, the pH range in which HPO ions dominate, was considered which in turn in necessary for the growth of lead hydrogen phosphate crystals. Characteristics of these crystals were carried out by infrared spectral analysis and microhardness study.

Nucleation and growth of CdC2O4·3H2O single crystals in silica gels

As part of our work on growth of cadmium oxalate single crystals in gels, we describe here variation of nucleation density and growth of these crystals as a function of concentration of feed solution, gel ageing, gel density, gel pH and intermediate neutral gel column. While high density and high pH gels have been found to produce opaque crystals, good quality transparent single crystals have been obtained in low density and low pH gels. It was observed that the intermediate neutral gel column and gel ageing considerably reduced the number of nucleation sites and increased the size of the crystals without affecting their quality. By concentration programming the size of the crystals increased.

Electrolytic growth and dielectric properties of magnesium hydrogen phosphate single crystals

AbstractThe growth of MgHPO4, magnesium hydrogen phosphate, (MHP) single crystals in silica gels under the influence of an externally applied uniform electric field is described. A controlled reaction between magnesium chloride and orthophosphoric acid by a diffusion process in the gel medium is employed. The bright, transparent MHP crystals upto 4 × 2 × 1 mm3 in sizes are grown at room temperature. The dielectric measurements are carried out in the temperature range between 300 to 650 K. The effect of the applied frequency on the dielectric constants and the dielectric losses are investigated. It is observed that the mechanism of the dielectric behaviour is different in the lower and higher frequency and temperature ranges. The activation energy of the oscillators are calculated and found to be 1.105 eV. Attempt is made to draw some qualitative conclusions, taking in view the existing theories of various kinds of polarization, and implications are discussed.

Nucleation density and electrolytic growth of lead hydrogen phosphate single crystals in silica gels

A detailed study of the variation in nucleation density and growth of lead hydrogen phosphate (LHP), PbHPO4, single crystals as a function concentration of feed solution, gel aging, gel density, gel pH and replenishment programme is presented. While high density and high pH gels produce opaque LHP crystals, good quality transparent LHP single crystals are obtained at low density and low pH gels. It is observed that gel aging considerably reduces the number of nucleation sites. The growth of LHP crystals in silica gels under the influence of an externally applied uniform electric field is also investigated, The implications are discussed.

Growth of Te(OH)6Na2HPO4 · H2O single crystals in silica gel and their characterization

AbstractSingle crystals of Te(OH)6Na2HPO4 · H2O were grown in silica gel medium using single‐test tube diffusion method. Hexagonal pyramidal and hexagonal tabular single crystals were obtained. Crystals were characterized by IR, X‐ray, and Raman studies.

Growth history of PbS single crystals at room temperature

The growth history of PbS single crystals in silica gels acidified with HCl and HClO4 has been studied. A morphological evolution from dendritic growth (along {100} in HCl medium and {111} in HClO4 medium) to single crystals with equilibrium shape has been observed. The morphogenetical process is related to the growth mechanism dominating at different growth stages. This explanation agrees with the change of supersaturation expected in diffusing-reacting systems and with the surface topography analysis carried out by scanning electron microscopy.

Dendritic Growth of Ammonium Tartrate Single Crystals in Silica Gel

AbstractDendritic growth of Ammonium tartrate single crystals in silica gel at 30 °C is reported. Main stem parallel to the ‘C’ axis is observed. Dendritic growth in initial and final stages with its surface structures are illustrated and described. Growth features are correlated to the growing conditions and reacting components.

Nucleation control and growth kinetics of ammonium hydrogen tartrate single crystals in silica gels

A detailed study of the variation in the nucleation density and growth of ammonium hydrogen tartrate (AHT) single crystals as a function of the concentration of the feed solution, the gel density, the gel pH, the gel aging time and the temperature is presented. Whereas opaque crystals were produced from high density high pH gels, good quality transparent single crystals were obtained in low density low pH gels. The use of intermediate neutral gel column and gel aging times considerably reduces the number of nucleation sites. The nucleation density decreases as the temperature increases. A simple procedure to control nucleation sites in gels was adopted and resulted in a dramatic increase in the size of the crystals. Kinetics studies of the nucleation and growth of AHT needle crystals showed that these crystals grow by a one-dimensional diffusion-controlled reaction between ammonium chloride and tartaric acid. The implications of this behaviour are discussed.

A new technique for the growth of tin, SnI 2 and SnI 4 single crystals

The growth of tin, SnI 2 and SnI 4 single crystals in silica gels under the influence of an externally applied uniform electric field is described. A controlled reaction between stannous chloride and KI by a diffusion process in the gel medium was employed. Three different phases, transparent white crystals of tin up to 8 mm in size, yellowish long needles of SnI 2 up to 13 mm in size and reddish octahedral SnI 4 crystals up to 5 mm in size, were grown at room temperature in same experimental set-up. The habit changes resulting from the different growth parameters and the variations in the electrical conductivities of SnI 2 and SnI 4 are also reported. Two distinct electrical conductivity processes were observed and are interpreted as extrinsic and intrinsic conductivities. Magnetic susceptibility measurements reveal the diamagnetic characteristics of these materials and the implications are discussed.

Nucleation and growth of SnI 4 single crystals in silica gels

A detailed study of the variation in nucleation density and growth of stannic iodide (SnI 4) single crystals as a function of concentration of feed solution, gel aging, gel density and temperature is presented. It has been observed that the low density of gel gives good transparent single crystals and gel aging considerably reduces the number of nucleation sites. It has been found that the nucleation density decreases as the temperature increases. A simple procedure to control nucleation sites in gels has been adopted which has resulted in a dramatic increase in the size of the crystals. The growth of SnI 4 in silica gels under the influence of an externally applied uniform electric field has also been investigated. The implications are discussed.

Nucleation and growth of KClO 4 single crystals in silica gels

As part of a continuing effort on the growth of KClO 4 single crystals in gels, this paper describes the variation of nucleation density and growth of these crystals as a function of concentration of feed solution, gel ageing, gel density, gel pH and intermediate neutral gel column. While high density and high pH gels have been found to produce opaque crystals, good quality transparent single crystals have been obtained at low density and low pH gels. It is observed that the intermediate neutral gel column and gel ageing considerably reduce the number of nucleation sites. A simple procedure to control nucleation sites in gels has been adopted, which has resulted in a dramatic increase in the size of the crystals.

The growth of single crystals of lead sulphide in silica gels at ambient temperatures - preliminary characterization and effect of various organic compounds as sulphide ion donors

The use of thioacetamide as sulphide ion donor for the growth of lead sulphide single crystals in silica gels at ambient temperatures is discussed. Data are presented on the chemical purity and certain pertinent electronic properties of the gel grown lead sulphide crystals. Other organo-sulphur compounds are experimentally evaluated as possible sulphide ion donors and compared with thioacetamide which compound has given the best results to date.