Papers by Keyword: Thermal Quenching

Abstract: A blue-emitting phosphor, NaBaPO₄:Eu2+, was prepared by solution combustion synthesis method, and its luminescence properties were investigated in detail. It was found that NaBaPO₄:Eu²⁺ could be efficiently excited by the UV-visible light of 230-420 nm and exhibited bright blue emission, which matched well with the emission wavelength of near-UV LED chips. NaBaPO₄:Eu²⁺ showed high thermally stable luminescence compared to commercial phosphor YAG:Ce³⁺. With the increase of the temperature, the normalized emission intensity of NaBa_0.98PO₄:0.02Eu²⁺ decreased to 92.3% of the initial value at 423 K, and the emission band exhibited a little blue-shift.

Abstract: Multiternary nitride and oxynitride compounds doped with rare earth ions, such as Eu2+ and Ce3+ have been enthusiastically applied as various phosphors to white LED. New red and green phosphors, CaAlSiN3:Eu and Ba3Si6O12N2:Eu, have been successfully synthesized, recently. The red phosphor has intense emission around 650 nm under two different irradiations at 405 and 455 nm from blue- and near UV-LED chips, respectively; while strong emission is observed around 520 nm from the green phosphor. Both phosphors also show small thermal quenching over the temperatures up to 150 °C. In addition, both LaSi3N5:Ce and La3Si8O4N11:Ce in lanthanum silicon nitride and oxynitride were examined as candidates for a blue phosphor in white LED with near UV-LED chip.

Abstract: Aluminum nitride ceramics were sintered with 1.0 and 4.8 mass% Ca3Al2O6 (C3A) as a sintering additive. Temperature dependence of cathodoluminescence (CL) for the ceramics was investigated in order to obtain information on lattice defects. The CL peak intensity at 3.5 eV in the ceramics sintered with 1.0 mass% C3A decreased with increasing temperature, so called thermal quenching. The maximum CL peak intensity of the ceramics sintered with 4.8 mass% C3A was much lower than that with 1.0 mass% C3A, reflecting that the oxygen-induced defect density dramatically decreased with increasing amount of C3A. In case of the ceramics sintered with 4.8 mass% C3A, the CL peak intensity at 3.4 eV showed the thermal quenching in the range of 130 - 350 K, whereas in the range of 80 - 130 K and 350 - 475 K, it increased with increasing temperature, so called “negative” thermal quenching. From the results, we suggest a presence of at least two trapping levels in the ceramics sintered with C3A.