Size and morphology control by planetary ball milling in CaAl2O4:Eu2+ phosphors prepared by Pechini method and their luminescence properties

Blue emitting CaAl2O4:Eu2+ (CA:Eu2+) phosphors were prepared by combining Pechini method and planetary ball milling, and their photoluminescence (PL) properties were investigated. A single phase monoclinic CA:Eu2+ phosphor was synthesized by Pechini process using two-step annealing; first annealing at 1400 °C in air and second annealing at 1450 °C in 5% H2/N2 atmosphere. The obtained CA:Eu2+ phosphor exhibited a blue emission at 440 nm under the excitation of λexc = 340 nm, but the particle size was unexpectedly large with irregular shape (5–50 μm). The subsequent planetary ball milling and two-step re-annealing produced more rounded powders (2–3 μm) with smoother surfaces. Its PL intensity increased to 135% compared to the phosphor synthesized by Pechini process and comparable to that of the commercial BaMgAl10O17:Eu2+ (BAM) phosphor.