2006, Vol.16, No.6

Journal of the Korean Crystal Growth and Crystal Technology 2023 KCI Impact Factor : 0.19

pISSN : 1225-1429 / eISSN : 2234-5078
https://journal.kci.go.kr/jkcgct

ZnO-doped near-stoichiometric LiNbO3 single crystals of 0.8~1.0 mm diameter and 30~35 mm length were grown by the micro-pulling down (m-PD) method. The structure of the grown crystals was confirmed by powder x-ray diffraction (XRD) patterns. Electron probe micro analysis (EPMA) showed that Zn ions were homogeneously incorporated in grown crystals. The threshold in ZnO doping level was confirmed that an abrupt change in the features of OH- absorption band as doping level reaching about 2 mol%.

The significant color enhancement in low quality Australian natural sapphire has been achieved by a hydrothermalmethod. The optimal conditions for the color enhancement of Australian natural saphire were as follows; hydrothermalreaction temperature: 320~350oC, duration : 3 days, hydrothermal solvent: 2 M NaOH solution. After the hydrothermaltreatment, Australian natural saphires of transparent colors were obtained, and their grades were found to be improvedfrom comercial to midle/top grade by value chart analysis.

Electrostatic spray pyrolysis, a novel fabrication technique, has been used in this study to prepare calcium phosphate nano powders. Final annealing was done at 400oC for 30 min in air. The hydroxyapatite - forming ability of the annealed powder has been evaluated in Eagle's minimum essential medium solution (MEM). X-ray diffraction analysis, field emission - scanning electron microscope, energy dispersive X-ray spectroscope, and Fourier transform infrared spectroscope were used to characterized the annealed powders after immersion in MEM. The powder with an amorphous structure induced hydroxyapatite formation on their surfaces after immersion for 15 days.