Narrow UVB-Emitted YBO(3) Phosphor Activated by Bi(3+) and Gd(3+) Co-Doping

Y(0.9)(Gd(x)Bi(1−x))(0.1)BO(3) phosphors (x = 0, 0.2, 0.4, 0.6, 0.8, and 1.0, YGB) were obtained via high-temperature solid-state synthesis. Differentiated phases and micro-morphologies were determined by adjusting the synthesis temperature and the activator content of Gd(3+) ions, verifying the hexagonal phase with an average size of ~200 nm. Strong photon emissions were revealed under both ultraviolet and visible radiation, and the effectiveness of energy transfer from Bi(3+) to Gd(3+) ions was confirmed to improve the narrow-band ultraviolet-B (UVB) ((6)P(J)→(8)S(7/2)) emission of Gd(3+) ions. The optimal emission was obtained from Y(0.9)Gd(0.08)Bi(0.02)BO(3) phosphor annealed at 800 °C, for which maximum quantum yields (QYs) can reach 24.75% and 1.33% under 273 nm and 532 nm excitations, respectively. The optimal QY from the Gd(3+)-Bi(3+) co-doped YGB phosphor is 75 times the single Gd(3+)-doped one, illustrating that these UVB luminescent phosphors based on co-doped YBO(3) orthoborates possess bright UVB emissions and good excitability under the excitation of different wavelengths. Efficient photon conversion and intense UVB emissions indicate that the multifunctional Gd(3+)-Bi(3+) co-doped YBO(3) orthoborate is a potential candidate for skin treatment.