D. Nagaraju

Dislocations, microhardness and optical studies on glycine potassium nitrate crystal

Single crystals of glycine potassium nitrate (GPN), a semiorganic nonlinear optical crystal, of dimensions 15×12×4 mm3 were grown in a period of 10 days. The defect content present in the crystals was estimated by chemical etching technique. The results indicate that the average dislocation density is about 4.1×103/cm2. The UV-Vis. studies indicate that the crystal has a wide transmission range. The Kurtz powder test indicates that the second harmonic generation efficiency of GPN is 2.5 times that of KDP. The load-hardness curves for GPN were studied over the load range 10-100 g. The anisotropy in hardness was studied using Knoop indentation technique.

Evaluation of mechanical properties of some glycine complexes

The variation of Vickers hardness with load for (101) glycine zinc chloride (GZC), (001) glycine lithium sulphate (GLS), (001) triglycine sulphate (TGS) and (010) glycine phosphite (GPI) crystals was studied. From the cracks initiated along the corners of the indentation impression, crack lengths were measured and the fracture toughness value and brittle index number were determined. The hardness related parameters viz. yield strength and Young’s modulus were also estimated. The anisotropic nature of the crystals was studied using Knoop indentation technique.

Growth and characterization of a nonlinear optical crystal: Bisglycine hydrogen chloride

Single crystals of bisglycine hydrogen chloride (BGHC), a semiorganic nonlinear optical crystal, of dimensions 13×6×4 mm3 were grown in a period of 10 days. The grown crystals were confirmed by powder XRD, FTIR and DSC studies. For the first time, the defect content present in the crystals was estimated by chemical etching studies. The results indicate that the average dislocation density is about 3.1×103/cm2. The load-hardness curves for BGHC were studied over the load range 10-100 g. The UV-Vis. studies indicate that the crystal has a wide transmission range. The Kurtz powder test indicates that the second harmonic generation efficiency of BGHC is almost two times that of KDP.

Indentation size effect on some glycine based nonlinear optical crystals

In this paper, the load dependence of Vickers microhardness has been studied on some as-grown faces of glycine complexes viz. glycine hydrofluoride (GHF), glycinium oxalate (GOX), bisglycine hydrogen chloride (BGHC) and glycine manganese chloride (GMC). The Indentation Size Effect (ISE) is examined and the load independent hardness values are determined from the theoretical models viz. Hays-Kendall approach, proportional specimen resistance (PSR) model and modified PSR model. The experimental results show that PSR model gives a poor fit of the experimental data whereas, the modified PSR model is found to be the most effective for describing experimental data and the nature of ISE.