Fluorescence Lifetime-Based Luminescent Thermometry Material with Lifetime Varying over a Factor of 50.

Recently, the growing demand for temperature detection is pushing forward the flourishing development of noncontact optical thermometry. Herein, a new red phosphor Sr2InTa1-xO6:xMn4+ (SIT:xMn4+) was first constructed and systematically investigated. Based on the fairly rapid decline of the lifetime from 0.403 to 0.008 ms by increasing the temperature from 25 to 450 K, a noncontact optical thermometer can be made from phosphor SIT:0.003Mn4+ with Sr = 1.396% K-1 at 375 K and Sa = 0.0012 K-1 at 300 K. Because the luminescence is based on the outermost 3d orbits of Mn4+, the lifetime of SIT:xMn4+ is quite sensitive to the temperature, leading to a rapid decline of the lifetime with the increase in temperature. Moreover, multiple rounds of variable-temperature studies were performed to demonstrate the stability and reversibility of SIT:0.003Mn4+. This work suggests that Mn4+-phosphors are promising candidates for application as optical thermometric material.

Utilizing the energy transfer mechanism to realize color tunable luminescence.

Bi3+/Eu3+ co-doped phosphors can realize multi-color luminescence by adjusting the concentration ratio, which makes it possible to manually control the emission color. On this basis, a series of Bi3+/Eu3+ co-doped phosphors SrLaGa3O7:xBi3+,yEu3+ were prepared. The existence of energy transfer from Bi3+ to Eu3+ was verified by spectral analysis. The emission spectra of SrLaGa3O7:xBi3+ show a wide-band peaking at 472 nm. For SrLaGa3O7:xBi3+,yEu3+, the Bi3+ → Eu3+ energy transfer occurs and a series of sharp emitting peaks of Eu3+ can be observed simultaneously. The relative luminescence intensity of Bi3+ and Eu3+ can be modulated by changing the relative concentrations of Bi3+ and Eu3+. Using this mechanism, the color tunable luminescence of SrLaGa3O7:xBi3+,yEu3+ from cyan, through white to orange, and finally to red is realized. By using a 320 nm UV chip and SLG:0.06Bi3+,0.07Eu3+ white phosphor, a white light-emitting diode (WLED) lamp was fabricated with chromaticity coordinates of (0.3199, 0.3083) and a color rendering index Ra of 82. This indicates that the prepared sample is a very promising candidate in the LED field.

A new type of phosphate-based phosphor Na3CsMg7(PO4)6:Eu2+/Mn2+ with high quantum efficiency and high thermostability.

The Eu2+ ion, with the 4f75d1 electronic configuration, is one of the most important activated ions due to its symmetry-allowed 4f → 5d electron transition. Herein, we successfully prepared a new type of blue phosphor, Na3CsMg7(PO4)6:xEu2+ (NCMP:xEu2+), in which Eu2+ occupies the Na+ sites of the host lattice. Under 395 nm light excitation, a broad emission band from 410 to 550 nm can be seen, peaking at 458 nm, due to the 5d → 4f transition of Eu2+. Moreover, Eu2+ can be used as a sensitizer ion in an NCMP host. For co-doping phosphor NCMP:0.18Eu2+/0.4Mn2+, both Eu2+ and Mn2+ emission bands can be seen using 395 nm as the excitation wavelength for the occurrence of Eu2+ → Mn2+ charge transfer. The optimized concentration of Eu2+ for NCMP:xEu2+ is x = 0.18, with high internal (IQE) and external quantum efficiencies (EQE) of 66.4% and 22.8%. The luminescence of NCMP:0.18Eu2+ has high thermostability with 77.3% the intensity at 450 K compared to that at 300 K. Finally, a white illuminating lamp was produced using a 395 nm UV chip, blue phosphor NCMP:xEu2+, green phosphor (Sr,Ba)2SiO4:Eu2+ and red phosphor CaAlSiN3:Eu2+ with CIE coordinates of (0.378, 0.369), color temperature (CCT) of 3971 K, and color rendering index (Ra) of 79.8.

Designing a Polyphosphate Polymorph of CsMg(PO3)3 as Host Lattice for Preparing Single Mn2+-Oxidation Doped Phosphor in the Open Environment.

Within Mn-activated phosphors, the oxidation state of Mn dopant strongly depends on the structural features of the host lattice. This paper reported a new polymorph of CsMg(PO3)3 (CMP) with a complicated three-dimensional (3D) framework of [Mg(PO3)3]∞ that is constructed by MgO6 octahedra and 1D infinite [PO3]∞ chains. Then we prepared a series of red phosphors CsMg1-x(PO3)3:xMn2+ (CMP:xMn2+) by high temperature solid state reactions in the open air. Powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and photoluminescence (PL) studies revealed the single Mn2+-oxidation. Under 404 nm light exciting, CMP:0.2Mn2+ can emit single-band emission at around 630 nm with full-width at half-maximum (fwhm) of 70 nm. Besides, CMP:0.2Mn2+ possesses excellent thermostability up to 450 K. These features indicate that CMP:0.2Mn2+ is suitable to be used for LED backlight display. Moreover, this work suggests that a host lattice with suitable structure feature can form single Mn2+-oxidation and is rigid enough to protect Mn2+ from being oxidized by O2 at high temperature.