Site Occupation and Luminescence of Novel Orange-Red Ca₃M₂Ge₃O₁₂:Mn²⁺,Mn⁴⁺ (M = Al, Ga) Phosphors

Abstract

s Ca 3 M 2 Ge 3 O 12 :Mn 2+ ,Mn 4+ (M = Al, Ga) with sufficient red light component were developed, and their lattice occupancy and luminescent properties of different color centers have been studied. In Ca 3 M 2 Ge 3 O 12 :Mn, the abnormal self-reduction of Mn 4+ to Mn 2+ occurs. The doped manganese ion (using MnO 2 as Mn source) occupies dodecahedron Ca 2+ site forming Mn 2+ (I) color center with orange emission, while it occupies octahedral Al 3+ /Ga 3+ site forming Mn 2+ (II) and Mn 4+ color centers with red and deep red light emission. The thermal quenching properties show that Ca 3 M 2 Ge 3 O 12 :Mn (M = Al, Ga) samples have low thermal quenching, and the thermal quenching of Mn 2+ (I) is lower than that of Mn 2+ (II) due to existence of more defects nearby the Mn 2+ (II) providing additional nonradiative recombination decay path. Ca 3 Al 2 Ge 3 O 12 :Mn has a lower thermal quenching than Ca 3 Ga 2 Ge 3 O 12 :Mn because the former possesses higher rigidity. The obtained results reveal that Ca 3 M 2 Ge 3 O 12 :Mn 2+ ,Mn 4+ (M = Al, Ga) has potential practical value in WLEDs. Moreover, the luminescence of Mn 2+ and Mn 4+ ions in a matrix provides a new strategy for designing and synthesizing new luminescent materials.

An organic–inorganic hybrid K2TiF6 : Mn4+ red-emitting phosphor with remarkable improvement of emission and luminescent thermal stability

“…They are attributed to the spin-forbidden d-d transition ( 2 E g / 4 A 2g ) of Mn 4+ , and are activated by the [MnF 6 ] 2À vibration mode. [19][20][21][22] Fig. 3(c) depicts the lifetime curves of KTF : Mn 4+ and KTF : MEAH + , Mn 4+ .…”

Efficient red and broadband near‐infrared luminescence in Mn2+/Yb3+‐doped phosphate phosphor

“…Figure 3 illustrates the excitation and emission spectra of LSPO:0.008Mn 2+ phosphor. When the monitoring wavelength is 616 nm, the PLE spectrum contains several main excitation bands at about 265, 320, 358, 414, 463, and 510 nm, which are attributed to the Mn 2+ −O 2− charge transfer band, 6 A 1 ( 6 S)→ 4 T 1 (P), 6 A 1 ( 6 S)→ 4 E( 4 D), 6 A 1 ( 6 S)→[ 4 A 1 ( 4 G), 4 E( 4 G)], 6 A 1 ( 6 S)→ 4 T 2 (G), and 6 A 1 ( 6 S)→ 4 T 1 (G) transitions of the Mn 2+ ions, respectively 14,53,54 . When excited by 414 nm, LSPO:0.008Mn 2+ emits red light at about 616 nm, originating from the 4 T 1 (G)→ 6 A 1 ( 6 S) transition of the Mn 2+ ions 55 .…”

“…wavelength is 616 nm, the PLE spectrum contains several main excitation bands at about 265, 320, 358, 414, 463, and 510 nm, which are attributed to the Mn 2+ −O 2− charge transfer band, 6 A 1 ( 6 S)→ 4 T 1 (P), 6 A 1 ( 6 S)→ 4 E( 4 D), 6 A 1 ( 6 S)→[ 4 A 1 ( 4 G), 4 E( 4 G)], 6 A 1 ( 6 S)→ 4 T 2 (G), and 6 A 1 ( 6 S)→ 4 T 1 (G) transitions of the Mn 2+ ions, respectively. 14,53,54 When excited by 414 nm, LSPO:0.008Mn 2+ emits red light at about 616 nm, originating from the 4 T 1 (G)→ 6 A 1 ( 6 S) transition of the Mn 2+ ions. 55 Pleasantly, when the prepared sample is excited by 300 nm light, an unexpected broad and smooth NIR emission band peaking at 800 nm (fwhm = 112 nm) is detected.…”

Improvement in luminescent properties and thermo-optical conversion mechanism of Na2SiF6:Mn4+,K+@GQDs

“…/ 4 A 2g d-d transition of Mn 4+ , 37,38 which is activated by the [MnF 6 ] 2À vibronic modes. 39 The details of the vibronic modes are as follows: 590 (as-n 3 ), 600 (as-n 4 ), 604 (as-n 6 ), 613 (ZPL), 622 (s-n 6 ), 626 (s-n 4 ) and 638 nm (s-n 3 ). Fig.…”