Theoretical and Experimental Investigations of Mn4+ Site Occupation in CaAl12O19. (23rd July 2021) - Sagayama, Musashi
Abstract : The local environment of Mn 4+ ions in CaAl12 O19 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 Mn 4+ ion when substituted for the Al 3+ ion in CaAl12 O19 . There are three crystallographically inequivalent octahedral sites available for the Mn 4+ ion in the CaAl12 O19 lattice. Crystal field calculations of the Mn 4+ 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 Mn 4+ concentration in CaAl12 O19 . The ESR measurement also suggested the multiple site occupation by the Mn 4+ ion in CaAl12 O19 . Additionally, the optimum concentration of Mn 4+ in CaAl12 O19 that produced the brightest phosphor was determined.