«Ellestadite»-type anionic [PO4]3– → [SO4]2– substitutions in β-Ca3(PO4)2 type compounds: A new route to design the inorganic phosphors

Deyneko, Dina V.; Titkov, V. V.; Fedyunin, Fedor; Spassky, D.; Волков, С. Н.; Borovikova, E. Yu.; Lazoryak, Bogdan I.; Aksenov, Sergey M.

doi:10.1016/j.ceramint.2022.05.077

Cited by 7 publications

(1 citation statement)

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“…It should be noted that similar regularities have also been observed in other types of phosphors, for example, in molibdates [ 20 ]. The positive effect of the presence of Zn 2+ in the crystal structure concerns not only the substitutions in the host lattice, but also the anionic substitutions [ 21 ].…”

Section: Introductionmentioning

confidence: 99%

Mn2+ Luminescence in Ca9Zn1–xMnxNa(PO4)7 Solid Solution, 0 ≤ x ≤ 1

et al. 2023

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The solid solution Ca9Zn1–xMnxNa(PO4)7 (0 ≤ x ≤ 1.0) was obtained by solid-phase reactions under the control of a reducing atmosphere. It was demonstrated that Mn2+-doped phosphors can be obtained using activated carbon in a closed chamber, which is a simple and robust method. The crystal structure of Ca9Zn1–xMnxNa(PO4)7 corresponds to the non-centrosymmetric β-Ca3(PO4)2 type (space group R3c), as confirmed by powder X-ray diffraction (PXRD) and optical second-harmonic generation methods. The luminescence spectra in visible area consist of a broad red emission peak centered at 650 nm under 406 nm of excitation. This band is attributed to the 4T1 → 6A1 electron transition of Mn2+ ions in the β-Ca3(PO4)2-type host. The absence of transitions corresponding to Mn4+ ions confirms the success of the reduction synthesis. The intensity of the Mn2+ emission band in Ca9Zn1–xMnxNa(PO4)7 rising linearly with increasing of x at 0.05 ≤ x ≤ 0.5. However, a negative deviation of the luminescence intensity was observed at x = 0.7. This trend is associated with the beginning of a concentration quenching. At higher x values, the intensity of luminescence continues to increase but at a slower rate. PXRD analysis of the samples with x = 0.2 and x = 0.5 showed that Mn2+ and Zn2+ ions replace calcium in the M5 (octahedral) sites in the β-Ca3(PO4)2 crystal structure. According to Rietveld refinement, Mn2+ and Zn2+ ions jointly occupy the M5 site, which remains the only one for all manganese atoms within the range of 0.05 ≤ x ≤ 0.5. The deviation of the mean interatomic distance (∆l) was calculated and the strongest bond length asymmetry, ∆l = 0.393 Å, corresponds to x = 1.0. The large average interatomic distances between Mn2+ ions in the neighboring M5 sites are responsible for the lack of concentration quenching of luminescence below x = 0.5.

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Section: Introductionmentioning

confidence: 99%

Mn2+ Luminescence in Ca9Zn1–xMnxNa(PO4)7 Solid Solution, 0 ≤ x ≤ 1

et al. 2023

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The Role of Anions in Rare-earth Activated Inorganic Host Materials for its Luminescence Characteristics

Reddy

2024

J Fluoresc

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This work is inspired from the comprehensive work done by our research team aimed at improving the efficiency of white light emitting diodes (LEDs) through improvements in the colour rendering index of the red light (CRI), one of the primary colours of white light. Such work is triggered through the incorporation of anions (BO33−, PO43−, SO42−), either individually or as an integral part of dopant activated inorganic phosphor host materials. Numerous host materials such as ZnO, Y2O3, Ca3(PO4)2, CaMoO4, ABPO4, ABSO4 (where A represents alkali metals and B alkaline earth metals) have been considered ideal hosts materials for studying luminescence properties of materials (including other phosphors). In addition, red emitting dopants such as Sm3+, Eu3+ and Ce3+ have been incorporated into these host materials to achieve a higher CRI of red colour, an essential component of white light. The role anions in various materials is multifaceted; firstly, it acts as sensitizer whereby it absorbs excitation energy and transfers it non-radiatively to the dopants, secondly, it acts as a charge compensator to dopants with a charge of + 3, thirdly, it creates crystal fields that affects the electronic transitions of the dopants and fourthly, it creates a stable crystal structure that allows for dopant embedding. By understanding the exact role of these anions and their interactions with the host lattice and dopant ions, we could further optimize the luminescent properties of these activated host materials, which leads to higher efficiencies and performances in white light-emitting diodes and other lighting technologies. This work is a comprehensive review of the work undertaken by our research team aimed at enhancing the luminescent properties of WLEDs.

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