Monodisperse micro-spherical Sr2–zMg1+yYzAl22–xO36:xMn4+ red phosphors

Abstract

With narrow red photoluminescence (PL) bands, tetravalent Mn4+ doped phosphors show promising prospect in commercial application to effectively expand color gamut of phosphor converted LED displays. Here, we report a type of Sr2–zMg1+yYzAl22–xO36:xMn4+ phosphors with regular cage-like micro-spherical morphologies. The micron size spherical precursors were synthesized with a propylene oxide (PO) driven fast sol–gel method. The cage -like spherical morphology is beneficial to efficiently trapping much incident light to enhance the PL of the phosphors. Being calcined at 1300 °C, Sr2MgAl21.978O36:0.022Mn4+ only exhibits the internal quantum efficiency (IQE) of 24.91%. With the Mg2+-Mn4+ codoping and Y3+/Sr2+ substituting strategies, to fulfill charge balance and produce John-Teller distortion, IQE of Sr2–zMg1+yYzAl22–xO36:xMn4+ can be further improved up to 36.45%. The CIE color coordinates of Sr2–zMg1+yYzAl22–xO36:xMn4+ under near ultraviolet excitation can be stably fixed to (0.723, 0.227) at deep red region. It thus finds a potential application as pc-LED display with much broader color gamut than that of the NTSC standard. Therefore, Sr2–zMg1+yYzAl22–xO36:xMn4+ micron size spheres can be employed as promising red phosphors for high performance LED displays.