Color tone tuning by partial Sr²⁺ substitution of Ba ²⁺ in the white phosphors Ba_1-y Sr_y La _2-x Dy_x ZnO₅ (x=0.01-0.2, y=0-0.65)

Ba_1-y Sr_y La_2-x Dy_x ZnO ₅ (x=0.01-0.2, y=0-0.65) phosphors were prepared by a solid-state reaction, and their photoluminescence properties were investigated for the conversion of the UV light emitting diode radiation to white light. The results showed that the maximum emission intensity of the samples without Sr ²⁺ substitution was achieved at the Dy³⁺ doping level x=0.07 under the UV excitation at 388 nm, and the Commission Internationale del'Eclairage (CIE) chromaticity coordinate of the total emissions was located at (0.256, 0.334). When substituted by Sr²⁺, the X-ray diffraction showed that the lattice constants and unit cell volumes of Ba_1-y Sr_y La_1.93 Dy_0.07 Zn_O5 (y=0-0.65) decreased linearly with the increasing Sr²⁺ content. The color tone of the Ba_1-y Sr_y La_1.93 Dy_0.07 ZnO₅ phosphors could be tuned by the amount of Sr²⁺ substitution as the consequence of the induced lattice distortion, which resulted in a change in the local site symmetry around the Dy³⁺ ions. The CIE chromaticity coordinate (x,y) of Ba_1-y Sr_y La_1.93 Dy_0.07 ZnO₅ phosphors varied from bluish white (0.256, 0.334) at y=0 to near white (0.315, 0.370) at y=0.65 under the UV excitation at 388 nm.