Eu 3+-doped CaZrO 3 , SrZrO 3 , and Mg 2+-or Sr 2+-co-doped CaZrO 3 were synthesized by conventional solid state reaction and their photoluminescence (PL) properties were characterized. The Eu 3+-doped CaZrO 3-based compounds exhibited characteristic emissions of Eu 3+ (f-f transition). The intensity of the main PL emission peak at 614 nm increased with Mg 2+ co-doping, while it decreased with the amount of co-doped Sr 2+. The site substituted by Eu 3+ cations in the CaZrO 3-based compounds was investigated by X-ray diffraction analysis and energy-dispersive X-ray analysis based on the electron channeling effects in transmission electron microscopy. The Eu 3+ cations were determined to occupy mainly the B site (Zr 4+) in CaZrO 3. The dominant Eu 3+ substitution site was also strongly influenced by the co-dopant, and the ionic radius of the co-dopant was identified as an important factor that determines the dominant Eu 3+ substitution site.
Eu 3+-doped SrIn2O4 phosphors were synthesized by the solid solution method at 1400 ºC in air. The chemical composition of the phosphors was systematically changed to study the relation between the Eu 3+ substitution site and photoluminescence (PL) properties. Under excitation of the 7 F0→ 5 L6 transition of Eu 3+ at 393 nm, the SrIn2O4:Eu 3+ exhibited dominant red emission peaks at 611, 616 and 623 nm, which are attributed to the electric dipole transition 5 D0→ 7 F2 of Eu 3+. The results of X-ray diffraction analysis combined with PL spectroscopic analysis revealed that Eu 3+ ions occupied two different crystallographic In 3+ sites in the host SrIn2O4, while it was found to be impossible to substitute Sr 2+ with Eu 3+ prior to the Eu 3+ substitution at the In 3+ sites in the SrIn2O4. The intensity of the red emission peaks increased with the total amount of dopant Eu 3+ ion at the two In 3+ sites, and reached a maximum at 25 mol% Eu 3+-doping (SrIn2-xO4:xEu 3+ , x=0.25). Moreover, a small amount (<10 mol%) of Eu 3+ at the Sr 2+ site in the SrIn2-xO4:xEu 3+ was found to contribute to enhance the red emission peak intensity at 616 nm. As a result, the highest red emission intensity evaluated as the total emission peak intensities at the 611, 616 and 623 nm was achieved for Sr0.92In1.75O4:0.33Eu 3+ in which Eu 3+ ion concentrations at the In 3+ and Sr 2+ sites were simultaneously optimized as 25 and 8 mol%, respectively (Sr1-yIn2-xO4:(x+y)Eu 3+ , x=0.25, y=0.08). This red emission intensity was 2.2 times higher than that of the phosphor without contribution of the Eu 3+ at the Sr 2+ site (SrIn2-xO4:xEu 3+ , x=0.25). The critical energy transfer distance of Eu 3+ ion in the Sr0.92In1.75O4:0.33Eu 3+ phosphor was determined to be 0.817 nm, and the electric multipolar interaction was suggested as the dominant mechanism for concentration quenching of PL emission due to Eu 3+ ions in the Eu 3+-doped SrIn2O4 phosphors investigated in this study.
Metalorganic precursor for aluminum nitride (AlN) ceramics was synthesized by reacting aluminum tri-chloride (AlCl 3 ) with bis(trimethylsilyl)carbodiimide (BTSC). Fourier transform infra-red (FT-IR) spectrum of the synthesized precursor exhibited characteristic absorption bands assigned to the carbodiimide (N=C=N) group at 21502250, and 851 cm
¹1, while the solid state 27 Al magic angle spinning nuclear magnetic resonance (MAS NMR) spectrum of the precursor exhibited single signal at 103 ppm which was thought to correspond to Al(N=C=N) 4 unit. To examine the potential as a precursor for AlN ceramics, the intrinsic thermal conversion behavior up to 1800°C of the synthesized precursor was investigated under argon atmosphere. X-ray diffraction analysis revealed that the crystallization of AlN was found to start above 800°C, and fully crystallized AlN ceramics was synthesized by the additional heat treatment at 1800°C. In addition to the FT-IR and NMR spectroscopic analyses for studying the synthetic parameters such as reaction temperature and use of catalyst for the formation of polymeric precursors derived from AlCl 3 and BTSC, the effects of heat treatment condition on the polymer/ceramics conversion yield, impurity and crystallinity of the AlN ceramics have been studied by using a thermogravimetric analyzer coupled with a quadrupole mass spectrometer (TG-MS). The results were discussed from a viewpoint to develop a novel synthesis method for AlN ceramics through the polymer precursor route.
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