Mn-activated K2ZrF6 and Na2ZrF6 phosphors: Sharp red and oscillatory blue-green emissions

Abstract

Mn-activated A2ZrF6 (A = K, Na) phosphors are synthesized by the chemical reaction method in HF-based solutions. The Mn-activated K2ZrF6 phosphor exhibits sharp red emission peaks at ∼630 nm, which are typically observed in various Mn4+-activated phosphors. The phosphor is, therefore, identified to be K2ZrF6:Mn4+. The Mn-activated Na2ZrF6 phosphor, on the other hand, shows a broad blue-green emission band with a peak at ∼520 nm while exhibiting an oscillatory feature. This emission band is considered to originate from the Mn2+ ion in the Na+−Na+ site of Na2ZrF6. Such an oscillatory feature has not been previously reported for phosphors. Fourier transform analysis yields a main oscillatory period of ∼0.10 eV together with a secondary oscillatory period of ∼26 meV. Although the origin of the oscillatory feature in Na2ZrF6:Mn2+ is unclear, it appears to be caused by an effect of the Mn2+-induced strain in the Na2ZrF6 host. Such unique luminescence properties of Na2ZrF6:Mn2+ are not only of technological importance but also of scientific interest.