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Investigation on the bright and stable upconversion (UC) phosphors with multicolor emissions is fundamental and significant for the frontier applications of display and temperature probe. Here, diverse emitting colors with blue, cyan and yellowish green, which are caused by the energy transfer and cross-relaxation processes, are obtained by altering Er3+, Tm3+and Yb3+concentrations in Er3+singly, Er3+- Tm3+- Yb3+co- and tri-doped double perovskite La2ZnTiO6(LZT) phosphors synthesized by a simple solid-state reaction. In addition, excellent infrared emission at 801 nm located at “first biological window” is collected in Tm3+-Yb3+co-doped phosphors. Meanwhile, the temperature sensing properties based on the thermally coupled levels (2H11/2/4S3/2) of Er3+ions were analyzed from 298 to 573 K of LZT:0.15Er3+/0.10Yb3+phosphor, demonstrating that the maximal sensitivity value is about 56 × 10−4 K−1 at 448 K. All these results imply that this kind of UC material has potential applications in display, bioimaging and optical device.

Green emitting BaAl1.4Si0.6O3.4N0.6:Eu2+ phosphors with a uniform sphere-like morphology were successfully prepared via molten salt synthesis (MSS) method using NaNO3 as the reaction medium. The obtained phosphors exhibited a broad excitation spectrum ranging from 250 to 460 nm and a strong green emission peak at 510 nm due to the 4f65d1-4f7 (8S7/2) transition of Eu2+ ions. Under excitation at 365 and 450 nm, the optimal emission intensities of the sample obtained by using molten salt are 17% and 13% higher than those of the sample prepared via conventional solid state (SSR) method, respectively. The quenching concentration of Eu2+ ions is 5 mol%, and dipole-dipole interaction is responsible for the concentration quenching of Eu2+ ions in this type of phosphor. The mechanism of thermal quenching is discussed by using the configuration coordinate model and thermal quenching temperature is [?]200degC. Elemental mapping and energy dispersive X-ray spectroscopy (EDS) spectra proved the formation of the desired BaAl1.4Si0.6O3.4N0.6:Eu2+ materials.

It is well known that cyan-emitting phosphors play a very important role in full-spectrum white LEDs. A large number of cyan-emitting phosphors have been reported in the past few years, however, most of them can only be effectively excited by near-ultraviolet light. There are very few cyan-emitting phosphors that can be intensively excited by blue light (440 and 470 nm). Here, a novel blue-light excitable cyan-emitting phosphor BaLu1.95Ce0.05Al2Ga2SiO12with excellent performance is reported. The cyan phosphor has a cubic structure in space group Ia3¯dwith a = 1.205379(3) nm, which can be easily obtained through a solid-state reaction pathway. The emission peak of the cyan phosphor is located at 500 nm and its internal quantum efficiency is as high as 90.01% when excited at 455 nm at 25 °C. The cyan phosphor exhibits superior resistance against thermal quenching of luminescence, and its intensity at 125 °C is as strong as 92.14% of the intensity at room temperature. Meanwhile, it also shows an outstanding resistance against water, where its luminescence intensity is hardly changed after being immersed in pure water for 528 h. The white LED lamp prepared by employing the obtained BaLu1.95Ce0.05Al2Ga2SiO12as cyan phosphor displays remarkable optical properties with CCT = 4441 K, Ra = 93.7, CRI = 90.4 and CIE 1931 (x, y) as (x = 0.3648, y = 0.3752). The experimental results demonstrate that BaLu1.95Ce0.05Al2Ga2SiO12is a promising cyan-emitting phosphor with great application potential in full-spectrum white LEDs.

BaY1.94-xAl4SiO12:0.06Ce3+, xPr3+(x= 0, 0.01, 0.02, 0.03 and 0.04) phosphors were successfully prepared via the solid-state synthesis method at 1450°C. The diffuse reflection spectra, emission spectra, thermal luminescence stability of the phosphors and the optical properties of the white LEDs fabricated by employing the phosphors were investigated. BaY1.94-xAl4SiO12:0.06Ce3+, xPr3+phosphors can be effectively excited by blue light. Excited by 450 nm, the emission intensity located at 613 nm of BaY1.94-xAl4SiO12:0.06Ce3+, xPr3+phosphor significantly increases as the Pr3+concentration increases, and the maximum intensity is reached at x= 0.02, but the luminescence intensity located at 540 nm of BaY1.94-xAl4SiO12:0.06Ce3+, xPr3+phosphor decreases as the concentration of Pr3+increases. The Ra value of the white LED fabricated by employing BaY1.92Al4SiO12:0.06Ce3+, 0.02Pr3+as yellow phosphor was better than that of the white LED made by using BaY1.94Al4SiO12:0.06Ce3+. All the experimental results demonstrate that the red region of the emission spectrum of BaY1.94Al4SiO12:0.06Ce3+phosphor could be effectively improved by co-doping Pr3+, however, the emission intensity and thermal quenching performance will be slightly weakened.