Green synthesis of K2TiF6:Mn4+ using KHF2 as accessory ingredient: A novel airtight solid-state strategy

In this work, an airtight solid-state strategy was developed for the synthesis of K2TiF6:Mn4+ phosphor without the usage of high concentration HF solution. By heating K2TiF6, K2MnF6 and KHF2 in a sealed container at 474 K for hours and then washing the as-synthesized samples several times, K2TiF6:Mn4+ phosphor was obtained. The microstructure, luminescent properties of the phosphor were investigated systemically. The reaction mechanism were investigated and discussed in detail. KHF2 is the key role to obtain the red phosphor, which provides additional pressure and HF gas atmosphere, works as reaction intermediate and contributes to Mn4+ doping into K2TiF6 host. By using as-prepared K2TiF6:Mn4+ phosphor as a red componet for warm W-LEDs, the high color rendering index (Ra = 84) and low color temperature (CCT = 3621 K) device performance proved that this environmental friendly synthesis method would be an efficient way to produce red fluoride phosphor for W-LEDs.