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Photoluminescence Properties of Double Perovskite Tantalates Activated with Mn4+, AE2LaTaO6:Mn4+ (AE = Ca, Sr, and Ba)

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journal contribution
posted on 15.08.2017, 00:00 authored by Yohei Takeda, Hideki Kato, Makoto Kobayashi, Shunsuke Nozawa, Hisayoshi Kobayashi, Masato Kakihana
Tetravalent manganese is known as one of the candidate luminous centers to obtain red emission. There are still unclear factors in Mn4+-activated oxide phosphors to achieve intense emission. In this paper, we studied the photoluminescence properties of double perovskite-type tantalates AE2LaTaO6 (AE = Ca, Sr, and Ba) activated with Mn4+. All AE2LaTaO6:Mn exhibited Mn4+-emission in the deep red region under excitation by near-ultraviolet-green light (300–570 nm) at room temperature. Co-substitution of Mg2+, Al3+, and Ti4+ compensates unbalanced charge caused by oxygen defects, resulting in the enhancement of Mn4+-emission. The present cosubstitution effect is different from the usual cosubstitution, such as the replacement of two Al3+ by Mn4+ and Mg2+, taking into consideration the charge balance between cations. Theoretical calculation of band structures based on density functional theory suggests the presence of two kinds of quenching schemes in AE2LaTaO6:Mn, photoionization and electron transfer from valence band to t2g orbitals of Mn.