M. J. Joshi

GROWTH AND CHARACTERIZATION OF BIS-THIOUREA STRONTIUM CHLORIDE SINGLE CRYSTALS

Bis-thiourea strontium chloride was synthesized and single crystals were grown by the slow solvent evaporation technique using aqueous solvent. The solubility curve was obtained and the determination of the induction period as well as the evaluation of kinetic parameters of nucleation was carried out. The powder XRD analysis suggested orthorhombic crystal structure. The FT-IR spectrum confirmed the presence of various functional groups. The thermo-gravimetry analysis was carried out and the crystals were found to be stable up to 170°C. Applying Coats and Redferm relation to the thermo-gram, the kinetic and thermodynamic parameters of dehydration were calculated. The dielectric study was carried out in the frequency range of applied field from 500 Hz to 1 MHz. The variations of dielectric constant, dielectric loss, AC resistivity and AC conductivity were studied with frequency. It was found that the dielectric constant and the dielectric loss decreased as the frequency of applied field increased, whereas the AC resistivity increased as the frequency increased.

FTIR and thermal studies of gel-grown, lead–cadmium-mixed levo tartrate crystals

Metal tartrate compounds find various applications. Lead tartrate is added in gasoline to prevent knocking in motors, and cadmium tartrate crystals possess piezoelectric nature. In the present study, lead–cadmium-mixed levo tartrate crystals were grown using silica hydro gel as growth medium. Long and dendrite-type white crystals were obtained. The crystals were characterized by EDAX, powder XRD, FTIR spectroscopy, TG, DTA, and DSC. The composition of the crystals was determined by EDAX. The FTIR spectra revealed the presence of water molecules, O–H, C–H, C–O, C–C, and C=O functional groups. TG curves suggested that the crystals were thermally unstable and decomposed into oxide through three stages. DTA curves showed endothermic and exothermic reactions.

Dielectric relaxation, protonic defect, conductivity mechanisms, complex impedance and modulus spectroscopic studies of pure and L-threonine-doped ammonium dihydrogen phosphate

Ammonium dihydrogen phosphate (ADP) has a wide range of applications in integrated and nonlinear optics. The dopant-like L-threonine has hydrogen-bonded side chain that causes defects in ADP. The pure and L-threonine-doped ADP crystals are grown using slow evaporation technique. The powder XRD patterns show the single-phase nature of pure and doped ADP. The dielectric constant and dielectric loss have shown the usual behaviour with respect to frequency and temperature. The protonic conduction is prevailing for electric transport, and from Jonscher’s plot, the correlation barrier hopping (CBH) and non-overlapping small polaron tunnelling (NSPT) conduction mechanism is confirmed. The Nyquist plot and modulus spectra show the presence of grain and grain boundary. The stretch exponent exhibits non-Debye-type relaxation. The activation energy of relaxation time for all samples is calculated. The modulus master curve and variation of Z″ and M″ versus angular frequency confirmed the proposed conduction. The nonlinear optical counterpart is in accordance with dielectric results.

Synthesis and characterization of struvite nano particles

Struvite, Ammonium Magnesium Phosphate Hexahydrate [(AMPH) - (NH4)MgPO4.6(H2O)], is one of the fascinating inorganic phosphate minerals. Struvite is one of the components of the urinary stones. Struvite occurs as crystallites in urine and grows as a type of kidney stone. In this study, struvite nano particles were synthesized by wet chemical technique. The aqueous solutions containing dissolved Mg(CH3COO)2.4H2O and (NH4)H2PO4 mixed at the Mg/P molar ratio of 1.00. The synthesized struvite nano particles were characterized by XRD, FT-IR, Thermal Analysis and TEM. From XRD, crystal structure of the nano particle was found to be orthorhombic and crystalline size was found to be within 11 to 26 nm. The FT-IR spectrum for the struvite nano particles confirmed the presence of a water molecule and metal-oxygen stretching vibration, O-H stretching and bending, N-H bending and stretching, P-O bending and stretching vibrations. The Thermal Analysis was carried out from room temperature to 900°C. From TEM analysis, ...

Preferred growth of bismuth single crystals at slow growth rates by Bridgman technique

Abstract Bismuth single crystals having low mosaic spread are used as filters for obtaining clean beam of thermal and cold neutrons. The present study is of the role of growth rate (1 to 6.5 cm/h) and temperature gradient (11.4, 18.5 and 22.2/dgC/cm) on the preferred orientation of the (111) cleavage plane of bismuth single crystals grown by the unseeded Bridgman technique. The results are interpreted to give understanding of the preferred orientation so that previously reported random orientation at growth rates below 2 cm/h and parallel translation of orientation versus growth rate plots at growth rates over 8 cm/h can be correlated.