title: Monodisperse colloidal spheres for (Y,Eu)2O3red-emitting phosphors: establishment of processing window and size-dependent luminescence behavior.
abstract: The urea-based homogeneous precipitation method was introduced in the preparation of monodisperse colloidal spheres for (Y0.95Eu0.05)2O3red-emitting phosphors, and the processing window was defined. Particle size and shape are significantly affected by the ion concentration and the urea/RE3+molar ratioR(RE3+=Y3++Eu3+). A low ion concentration is beneficial in forming monodisperse spheres and extending their formation domain. IncreasingRresults in a gradual change in the composition of spherical particles from the core-shell Eu(OH)CO3@Y(OH)CO3structure to a homogeneous solid solution, thereby significantly lowering the calcination temperature at which precursors convert to oxides. Upon UV excitation into the charge-transfer band at 254 nm, the uniform phosphor spheres of (Y0.95Eu0.05)2O3exhibit typical red emissions at 613 nm; the emission is stronger from larger particles mainly because of their smaller surface area. Both the luminescence intensity and quantum efficiency of the oxide phosphors increase with elevated calcination temperatures. The spherical shape and excellent dispersion of the precursor particles (∼450 nm in diameter) have been well retained after calcination at 1000○C for 4 h, and the resultant oxide phosphors exhibit external and internal quantum efficiencies of 50 and 82%, respectively.
authors.affiliation: Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), School of Materials and Metallurgy, Northeastern University, Shenyang, Liaoning, 110004, China; Advanced Materials Processing Unit, National Institute for Materials Science, Sengen 1-2-1, Tsukuba, Ibaraki, 305-0047, Japan.
authors.forename: Qi
authors.initials: Q
authors.lastname: Zhu
authors.affiliation: Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), School of Materials and Metallurgy, Northeastern University, Shenyang, Liaoning, 110004, China; Advanced Materials Processing Unit, National Institute for Materials Science, Sengen 1-2-1, Tsukuba, Ibaraki, 305-0047, Japan.
authors.forename: Ji-Guang
authors.initials: JG
authors.lastname: Li
authors.affiliation: Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), School of Materials and Metallurgy, Northeastern University, Shenyang, Liaoning, 110004, China.
authors.forename: Xiaodong
authors.initials: X
authors.lastname: Li
authors.affiliation: Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), School of Materials and Metallurgy, Northeastern University, Shenyang, Liaoning, 110004, China.
authors.forename: Xudong
authors.initials: X
authors.lastname: Sun
authors.affiliation: Advanced Materials Processing Unit, National Institute for Materials Science, Sengen 1-2-1, Tsukuba, Ibaraki, 305-0047, Japan.
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Sakka
keywords: colloidal monodisperse spheres; optical materials; optical spectroscopy; powder processing