Er^(3+) 이온이 첨가된 Calcium Niobium Gallium Garnet 결정의 형광특성

Abstract

Luminescence properties of Er^(3+) ions doped in Calcium Niobium Gallium Garnet (Ca₃(NbGa)2-xGa₃O_(12);CNGG) crystal are investigated by laser excitation spectroscopy in the temperature region 15K - room temperature. Broad absorption band peaking at around 325nm is observed in the spectral range 364 - 294 nm. The 325nm band was also observed in non-doped CNGG. Therefore it is suggested that this band is attributable to a charge transfer band of oxygen-vacancies. Time-resolved emission spectra of Er3+ in CNGG are measured, together with the luminescence decay by the 355 and 532 and 266 nm pulsed laser excitations. Different emission spectra are observed at different time delays of 250ns and 5 μs. Rise times are observed for several emissions under 355 nm excitation but not observed under 532 and 266 nm excitation. It is suggested that there exist different sites for the Er^(3+) ions and energy transfer occurs between the Er^(3+) ions. CNGG has a disordered structure due to enormous variety of different types of ions and cationic vacancies in the regular sites of host lattice. In the garnet expressed by the chemical formula C₃A₂D₃O_(12) like CNGG(Ca₃(NbGa)_(2-x)Ga₃O_(12)), the C, A, and D ions occupy the different crystallographic sites. The Er^(3+) ions in CNGG can occupy the Ca^(2+), Ga^(2+), and Nb^(5+) lattice sites. In this presentation, the results are discussed in relation with structural properties of the CNGG lattice.