Structural change induced by thermal annealing of red-light-emitting ZnSnF6 ∙ 6H2O:Mn4+ hexahydrate phosphor

Abstract

Effects of thermal annealing on the red-emitting ZnSnF6 ∙ 6H2O:Mn4+ hexahydrate phosphor properties were investigated using X-ray diffraction measurement (XRD), photoluminescence (PL) analysis, and Raman scattering spectroscopy. Thermal annealing was performed at Ta = 50 to 400 °C in air for 1 h. Mn4+-related red emission wavelengths were redshifted about 5 nm after annealing at Ta ≥ 200 °C with greatly decreased emission intensities. This change in PL spectral feature was attributed to the dehydration of the hexahydrate phosphor, supported by the XRD and Raman scattering results. The XRD and PL intensity analyses determined thermal decomposition energies of ∼0.3 eV from the ZnSnF6 ∙ 6H2O hexahydrate to anhydrate and of ∼0.9 eV from the ZnSnF6 anhydrate to metallic fluorid/oxide (ZnF2/SnO2). A comparative discussion was given on the PL properties of two different Mn4+-activated phosphors, Ba–IV–F6:Mn4+ anhydrate and Zn–IV–F6 ∙ 6H2O:Mn4+ hexahydrate phosphors with IV = Si, Ge, and Sn.