Dielectric properties of cobalt doped cadmium oxalate crystals

Abstract

CoxCdl_xC2044H20 crystals grown by gel technique are characterized for dielectric properties by optical absorption measurements. Loss curve shows a relaxation peak at 500 KHz corresponding to a relaxation time of 0"3 #s. Cole-Cole diagrams give exponent of universal power law to be equal to 0'22. Optical absorption shows peaks due to Co ÷ 2 ion and water of hydration. An attempt is made to understand the results.

Etching and Micro-Topographical Studies of Barium Oxalate Crystals Grown in Agar Gel

“…From these Arrhenius graphs, the values of activation energy E and pre-exponential factor A thus calculated are shown in Table 1. It was observed that the values of activation energy E, for etching in HCl, NH 4 Cl and HNO 3 solutions are close to each other, though the rates of dissolution in these etchants are largely different. BaCl 2 and NH 4 Cl + HCl etch solutions are characterized by relatively larger and lower values of activation energies respectively.…”

“…BaCl 2 and NH 4 Cl + HCl etch solutions are characterized by relatively larger and lower values of activation energies respectively. The faster etch rate in NH 4 Cl-HCl may not be due to the energies of the atoms at the surface or due to their geometric configuration [23], but may be due to both; the chemical reaction and diffusion are operating simultaneously, that makes the etching or dissolution process less sensitive to temperature change, and hence a very low value of activation energy was observed. The etchants such as HCl, HNO 3 reacts with the crystal surface to form oxalic acid, which in turn dissolves in water.…”

“…1) The mechanism of etching barium oxalate in etchant such as 1 M HNO 3 is reaction rate controlled whereas in the case of 4 M NH 4 Cl, 4 M BaCl 2 it is diffusion rate controlled. 2) The observation of Tuck [25] that the activation energy for reaction rate controlled etching is more than that of the diffusion rate controlled one, is not found true for barium oxalate dissolution.…”

“…The agar gel technique is an inexpensive and simple for growing single crystals of certain class of materials like alkaline earth metal oxalates [3]. Oxalate crystals are insoluble in water and decompose before melting [4]. Therefore, single crystals of these materials cannot be grown by either slow solvent evaporation or melt techniques but they can be suitably grown by gel method.…”

Dielectric and Theoretical Studies on L-histidinium 2-nitrobenzoate NLO Single Crystal

“…From the figs, it is found that the values of dielectric constant and dielectric loss decreases with the increase in frequency and dielectric constant of crystal at higher frequencies is almost constant. The very high value of ɛ r at low frequencies may be due to the presence of all the four polarizations, namely space charge, orientional, ionic and electronic polarizations and its low value at high frequencies may be due to the loss of significance of these polarizations gradually [17]. The value of dielectric loss at high frequencies reveals the high optical quality of the crystal with lesser defects, which is the desirable property for NLO applications [18].…”