CRYSTALLIZATION PROCESS OF MGSIO3 GEL AND INFLUENCE OF CRYSTALLIZATION ON LUMINESCENCE OF EU3+ IONS

Crystallization process of MgSiO3 gel and influence of crystallization on luminescence of Eu3+ ions have been investigated. The residual sol vents in gels were vaporized in the temperature range between room tem perature and 300 degrees C, and organic compounds chemically bound to Mg and Si were eliminated between 350 and 430 degrees C. The exothermi c effect on the DTA curve corresponding to crystallization of MgSiO3 g el appeared at about 850 degrees C, and the activation energy of cryst allization was found to be about 490 kJ/mol. When gels were fired betw een 750 and 1050 degrees C the crystalline phase was principally the c linoenstatite. The luminescence of Eu3+ ions was predominantly influen ced by the crystallization gels. The intensity of excitation and emiss ion bands in gel-derived crystals was much stronger than that in dried gel, and the strongest excitation band also transformed from 393 nm i n dried gel to 250 nm in gel-derived crystals, which can be attributed to a dominant charge transition from ligands (O2- ions) to Eu3+ ions in gel-derived crystals. It was also found that in gel-derived crystal s the main band corresponding to D-5(0) --> F-7(2) transition (616 nm) was split by the crystal field into three bands, the band correspondi ng to D-5(0) --> F-7(1) transition (593 nm) into three bands and the b and corresponding to D-5(0) --> F-7(4) transition (690 nm) into two ba nds; the energy level split of Eu3+ ions was markedly changed with the fired temperature gels.