Blue-white-orange tunable Ba6Ca3YAlSi6O24:Eu2+, Mn2+ phosphors for NUV-pumped LEDs

Abstract

Near-ultraviolet (NUV)-excitable phosphors composed of Ba6-m-nEumMnnCa3YAlSi6O24 (m = 0.01–0.5, n = 0–0.5) were prepared via a solid-state reaction in a reducing atmosphere. The X-ray diffraction patterns of the single-phase orthosilicate Ba6-m-nEumMnnCa3YAlSi6O24 phosphors were examined to index the peak positions. The photoluminescence (PL) emission spectra of the phosphors were clearly observed under 365-nm excitation. The critical distance and electric multipole interaction were exploited. The dependence of the luminescent intensity of the Mn2+ co-doped host lattice on the Eu2+ content was also investigated. Co-doping Mn2+ and Eu2+ emitters in the Ba5.8-nEu0.2MnnCa3YAlSi6O24 phosphors enabled efficient energy transfer from Eu2+ to Mn2+; the energy-transfer mechanism is also discussed. The Commission Internationale de I'Eclairage (CIE) coordinates near the blue, white, and orange regions of the obtained phosphors were observed. Thermal quenching of Ba5.7Eu0.2Mn0.1Ca3YAlSi6O24 phosphor was exploited in the temperature range of 298–448 K and at 193 K. The activation energy for thermal quenching of the phosphors was calculated. The relative quantum efficiency (QE) of Ba5.7Eu0.2Mn0.1Ca3YAlSi6O24 phosphor was compared with that of the commercial YAG:Ce and the previously studied Ba8.8Eu0.1Mn0.1Y2Si6O24 phosphor. NUV-executable white Ba5.7Eu0.2Mn0.1Ca3YAlSi6O24 phosphor with a 365-nm LED chip was fabricated and the internal QE was measured. The color rendering index (CRI, Ra) at correlated color temperature (CCT) with the CIE coordinates was exhibited for the LEDs.