Strontium tartrate trihydrate (STT) crystals have been grown in silica hydrogel. Various polarization mechanisms such as atomic polarization of lattice, orientational polarization of dipoles and space charge polarization in the grown crystals have been understood using results of the measurements of dielectric constant (ε ε′ ′) and dielectric loss (tan δ δ) as functions of frequency and temperature. Ion core type polarization is seen in the temperature range 75-180°C, and above 180°C, there is interfacial polarization for relatively lower frequency range. One observes dielectric dispersion at lower frequency presumably due to domain wall relaxation.

Results of a study on nucleation kinetics, growth, and characterization of strontium tartrate trihydrate single crystals in silica hydrogel are described. The basic structure, composition, and perfection of the grown crystals were determined by XRD, EDAX, and laser scattering tomography. It was found that experimental conditions, such as pH and density of gel, concentration and volume of supernatant liquid, aging and quality of gel, have a strong influence on the nucleation kinetics and growth of the crystals. The effect of experimental conditions on growth kinetics has been qualitatively explained from the standpoint of the classical nucleation theory.

No abstract

No abstract

Efforts have been successful to crystallize the electroceramic compound of cadmium tartrate through silica hydrogel. Analysis of thermograms reveals decomposition of the crystals to take place within the temperature range 65 to 442°C in air atmosphere. Some important characteristic data, i.e., valance electron plasma energy, Penn gap, Fermi energy, interionic distance, electronic polarizability have been obtained. The DC conductivity of the crystal typically lies between the conductivities of metal and insulator and we derived several pertinent parameters such as hopping energy, hopping distance, coulomb gap, etc. The micromechanical indentation of the crystal shows nonlinear variation of the impact microhardness as a function of the applied load. The estimation of fracture toughness, fragility coefficient and yield strength has too been made for the synthesized crystal.