Synthesis and properties of Rb₂GeF₆:Mn⁴⁺red-emitting phosphors

Abstract

Rb 2 GeF 6 :Mn 4+ red-emitting phosphors were synthesized by coprecipitation and their structural and optical properties were investigated by laser microscopy observation, X-ray diffraction (XRD) analysis, photoluminescence (PL) analysis, PL excitation (PLE) spectroscopy, and PL decay measurement. Single-crystalline ingots in the form of a hexagonal pyramid were prepared with a basal plane diameter of >2 mm. The XRD analysis suggested that Rb 2 GeF 6 crystallizes in the hexagonal structure (C 4 6v ¼ P6 3 mc) with a = 0.5955 nm and c = 0.9672 nm. The phosphor exhibited the strong Mn 4+ -related zero-phonon line (ZPL) emission peak typically observed in host crystals with piezoelectrically active lattices such as a hexagonal lattice. The quantum efficiencies of the bulk ingot and powdered samples were 87 and 74%, respectively, with nearly the same luminescence decay time of >6 ms. The exact ZPL energies and related crystal-field and Racah parameters were obtained from the PL and PLE spectra by Franck-Condon analysis. Temperature-dependent PL intensities were analyzed from T = 20 to 500 K using a thermal quenching model by considering Bose-Einstein phonon statistics. A comparative discussion on the phosphor properties of Rb 2 GeF 6 :Mn 4+ and Rb 2 MF 6 :Mn 4+ with M = Si and Ti was also given.

BaTiF6:Mn4+ Red Phosphor: Synthesis of Single Crystals at Room Temperature and the High Hydrolysis-Resistant Property

“…Many strategies have been proposed to prevent the [MnF 6 ] 2– group from hydrolysis. We have classified them into the following six classes, (1) coating with a hydrophobic organic compound, (2) coating with an inorganic layer, (3) self-coating to form a core–shell structure, (4) reductive treating to form Mn 4+ -rare surface passivation, (5) recrystallization by hydrothermal treatment, and (6) preparation of bulk single-crystal phosphor. − For the last strategy, our study demonstrates that the Na 2 SiF 6 :Mn 4+ single crystals indeed experience a much slower hydrolysis-induced deterioration than its polycrystalline powdery form. Furthermore, we recently compared the deterioration behavior of BaSiF 6 :Mn 4+ , Na 2 SiF 6 :Mn 4+ , and (NH 4 ) 2 SiF 6 :Mn 4+ phosphors in water and further find that the deterioration rate is closely related to their specific solubility.…”

Towards improved waterproofness of Mn4+-activated fluoride phosphors

“…The QE ( λ ex = 475 nm) reached 92% for the Rb 2 TiF 6 :Mn 4+ single crystal phosphor. Later, in 2018, they 31 also reported the growth of Rb 2 GeF 6 :Mn 4+ single crystal phosphor with a basal plane diameter of >2 mm via a similar co-precipitation growth method, and the QE for the bulk ingot was 87% ( λ ex = 475 nm).…”

The qualities of dyed YAG:Ce3+@SiO2 for WLEDs via energy conversion

“…Luminescent efficiency, excellent color rendering indices (CRI), and a variety of other enhanced qualities have been developed in this general lighting industry in previous decades [3], [4]. Besides the popularly used LED lights that are mostly relied on phosphorusconverting LEDs (pc-LEDs) because of convenience, dependability, and low cost of production, white-colored light-emitted diodes (WLEDs) are created by fusing blue, green, and red LED chips [5]. The original commercially available WLEDs were made from fusing a yellowish-emitted garnet phosphorus, Y3Al5O12:Ce 3+ (YAG:Ce 3+ ), featuring a blue-emitted-LED chip.…”