MORPHOLOGICAL CONTROL OF SN2-CARBONATE PHOSPHORS BY CRYSTALLIZING AMORPHOUS CALCIUM-CARBONATE AND ITS FLUORESCENCE PROPERTY( DOPED CALCI UM)

Morphological control of Sn2+ doped calcium carbonate phosphors by cry stallizing amorphous calcium carbonate formed from aqueous solution re action of CaCl2-(NH4)(2)CO3-SnCl2 system and its fluorescence property were investigated. Amorphous calcium carbonate changed into spherical and platelike vaterites at 15-50 degrees C and needlelike aragonite a bove 60 degrees C. In order to obtain calcite, a suspension of vaterit e formed at 20 degrees C by crystallizing amorphous calcium carbonate was kept at 90 degrees C for 120 min. The content of Sn2+ in platelike vaterite crystal was Sn/CaCO3 mol% of approximately 0.4 and was about 4 times as compared with that of rhombohedral calcite crystal. The em ission spectrum of rhombohedral calcite phosphors with Sn2+ of 0.04 mo l% showed bright blue fluorescence at 465 nm. Its optimum excitation w avelength was wavelength of ultraviolet irradiation at 255 nm.