Dual-mode photoluminescence from nanocrystalline Mn2+-doped Li,Zn-aluminosilicate glass ceramics
We report on the photoluminescence (PL) of Mn2+-doped (Li+, Zn2+) aluminosilicate glasses and glass ceramics. Glass ceramics are fabricated by controlled crystallization of as-melted precursor glasses. X-ray diffraction (XRD), electron spin resonance (ESR) and PL analyses indicate precipitation of Li4–2(x+y)ZnxMnySiO4, with relatively low x and y values during the earlier phase of crystallization and x→1 in the later phase. During the crystallization process, Mn2+ ions, octahedrally coordinated in the precursor glass, partially precipitate on tetrahedral Zn2+ sites. This gives rise to the simultaneous occurrence of green and red luminescence, respectively, due to spin-allowed 4T1(G)→6A1(S) and spin-forbidden 4T1g(G)→6A1g(S) in IVMn2+ and VIMn2+. Accordingly, the amount of IVMn2+ species, the ratio of IVMn2+/VIMn2+ and, hence, the ratio between green and red photoemission bands can be controlled by the temperature at which the glass ceramics are produced. FWHM of the resulting emission spectrum can be increased from about 100000 to about 50000 cm−1. In parallel, as a result of multiple scattering, emission intensity appears to generally increase with increasing degree of crystallization.
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Document Type: Research Article
Publication date: April 1, 2011