Theoretical and Experimental Investigations of Mn⁴⁺ Site Occupation in CaAl₁₂O₁₉

Abstract

The local environment of Mn4+ ions in CaAl12O19 has been studied by electron spin resonance (ESR) measurements and by spin-polarized first principles calculations within a density functional theory to determine the site that is occupied by the Mn4+ ion when substituted for the Al3+ ion in CaAl12O19. There are three crystallographically inequivalent octahedral sites available for the Mn4+ ion in the CaAl12O19 lattice. Crystal field calculations of the Mn4+ energy levels for the preferred site were performed and shown to be in good agreement with the experimental spectroscopic data. ESR measurements confirmed the tetravalent oxidation state of Mn ion and showed that the local environment of the Mn ion was independent of the Mn4+ concentration in CaAl12O19. The ESR measurement also suggested the multiple site occupation by the Mn4+ ion in CaAl12O19. Additionally, the optimum concentration of Mn4+ in CaAl12O19 that produced the brightest phosphor was determined.

First-Principles and Experimental Study of Trace Impurities and Near-Infrared Emission in Alkaline Earth Hexaaluminates

“…The first two bands decrease in intensity with increasing concentration of Fe 3+ , whereas the ∼810 nm band increases in intensity up to 1 mol % Fe 3+ . The 653–656 nm band and associated structure has been the subject of several previous reports and is due to the 2 E → 4 A 2 transition of Mn 4+ . − The excitation wavelengths in Figure c correspond to the transitions from the 4 A 2 ground state to 4 T 2 (468 nm), 4 T 1 , 2 T 2 (395 nm), and Mn–O CT (343 nm) levels . The weak ∼400 nm emission band in Figure a is discussed later.…”

“…29−32 The excitation wavelengths in Figure 5c correspond to the transitions from the 4 A 2 ground state to 4 T 2 (468 nm), 4 T 1 , 2 T 2 (395 nm), and Mn−O CT (343 nm) levels. 33 The weak ∼400 nm emission band in Figure 5a is discussed later. The 806−814 nm emission band has recently been assigned to the 6s6p → 6s 2 transition of Bi 3+ at Al 3+ sites.…”

Geometrical and Electronic Structure Analysis of Mn‐Doped CaMO3 (M = Ti, Zr, and Sn)

“…For the rare-earth free efficient red phosphors, Mn 4þ is one of the candidates as an emission center ion. Several efficient red emission phosphors doped with Mn 4þ were already reported for Mn-doped fluorides [1][2][3][4][5][6] such as K 2 SiF 6 and oxides [7][8][9][10][11][12] such as CaAl 12 O 19 and Mg 2 TiO 4 . In order to understand luminescence characteristics and design new phosphors doped, it is essential to know the local environment of the doped ions in an atomic scale and the electronic structures of Mn-doped materials.…”

“…Recently, local environment of doped Mn 4+ ions was investigated by combined use of electron spin resonance (ESR) measurements and the first‐principles calculations within a density functional theory for Mn‐doped CaAl 12 O 19 . [ 12 ] A series of orthorhombic perovskite structured CaMO 3 doped with Mn ions have been also investigated as efficient red emission phosphors for Mn‐doped CaTiO 3 , [ 13 ] CaZrO 3 , [ 14,15 ] and CaSnO 3 . [ 16 ] However, valence state of the doped Mn ions and detailed geometrical and electronic structures have not yet been clearly determined in these earlier studies.…”

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Recently, local environment of doped Mn 4þ ions was investigated by combined use of electron spin resonance (ESR) measurements and the first-principles calculations within a density functional theory for Mn-doped CaAl 12 O 19 . [12] A series of orthorhombic perovskite structured CaMO 3 doped with Mn ions have

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