Novel BaGe1-xSixF6: Mn4+ (0 ≤ x ≤ 1) red phosphors for warm white LEDs: Hydrothermal synthesis and photoluminescence properties

Abstract

Novel Mn4+-doped BaGe1-xSixF6 (0 ≤ x ≤ 1) red-emitting phosphors were successfully synthesized through a facile and efficient hydrothermal route. The effects of Ge/Si ratio (x) on the microstructure, chemical composition and optical features of as-synthesized BaGe1-xSixF6: Mn4+ crystals were studied in detail. The BaGe1-xSixF6: Mn4+ solid solutions have rhombohedral structure, and the as-obtained samples contain well crystallized microcrystals with predominant rod-like morphology. Under the excitation at 471 nm, the BaGe1-xSixF6: Mn4+ microcrystals exhibit a series of sharp characteristic emission bands of Mn4+ in red range (610–650 nm), showing the strongest red emission at∼636 nm. It is found that the PL intensity, fluorescence decay time and thermal stability of the BaGe1-xSixF6: Mn4+ samples can be efficiently improved through rational regulating the Si4+ concentration, displaying variation tendency of increasing firstly and then decreasing with the ascending concentration of Si4+. A set of warm white light-emitting diodes by merging BaGe1-xSixF6: Mn4+ phosphors, blue chip (∼460 nm) and commercial YAG: Ce yellow phosphor possess high color rendering index (CRI, Ra > 80) and low correlated color temperature (CCT < 4500 K), having potential application in indoor lighting.