A high-luminescence BaZrSi3O9:Eu2+ blue-green-emitting phosphor: Synthesis and mechanism

A high-luminescence BaZrSi3O9:Eu2+ (BZSE) blue-green-emitting phosphor was successfully synthesized by a gelation method using propylene glycol-modified silane (PGMS). After heat treating under Ar-H2 flow followed by annealing in air, the synthesized phosphor exhibited a strong emission intensity approximately three times stronger than that of commercial BaMgAl10O17:Eu2+ (BAM:Eu2+) along with high internal and external quantum efficiencies of 74.3% and 58.4% at 405 nm excitation, respectively. We considered the high emission efficiency of the BZSE samples in terms of (1) the self-absorption by the host crystal, (2) change in Eu valence in the phosphor during annealing in air, and (3) stability of Eu substitution at the Ba2+ site in BaZrSi3O9 (BZS). The results indicate that the high emission efficiency of the BZSE samples originated from (1) the reduction in self-absorption caused by the decrease in oxygen deficiency and (2) the suitable quantity (approximately 4 mol%) of Eu2+ that was retained even after high-temperature annealing in air, which is attributed to the stability of the Eu substitution site in BaZrSi3O9.