Host-sensitized borate phosphors ZnGdB₅O₁₀:Mn²⁺/Dy³⁺/Sm³⁺ 

Photoluminescence energy transfer is a good strategy to enhance the efficiency or tuning of emission colors. A phosphor host containing Gd³⁺ may facilitate the host-sensitization effect and transfer the so-absorbed photon energy to other activators. Zn_1-MnGdB₅O₁₀ (0.005 ≤ x ≤ 0.07), ZnGd_1-DyB₅O₁₀ (0.01 ≤ y ≤ 0.09), and ZnGd_1-SmB₅O₁₀ (0.01 ≤ z ≤ 0.09) were synthesized via the traditional high-temperature solid-state method. A powder X-ray diffraction technique was employed to confirm the phase purity and successful doping. In all phosphors, by monitoring the characteristic emission of Mn²⁺, Dy³⁺ and Sm³⁺, the excitation spectra of all were found to contain the typical absorption belonging to Gd³⁺; in addition, the largely shortened fluorescence lifetimes of Gd³⁺ after Mn²⁺, Dy³⁺ or Sm³⁺ doping strongly proved the existence of the host-sensitization effect. Along with Gd³⁺-sensitization, Mn²⁺ doped at the Zn²⁺ site emits a close-to-ideal red light. Dy³⁺ and Sm³⁺ doped at the Gd³⁺ site emit close to white and orange light, respectively. The calculated internal quantum efficiency is 25.5% for Zn_0.995Mn_0.005GdB₅O₁₀, 17.0% for ZnGd_0.97Dy_0.03B₅O₁₀ and 17.4% for ZnGd_0.97Sm_0.03B₅O₁₀. The high thermal stability of the photoluminescent emission for Mn²⁺, Dy³⁺, and Sm³⁺ can be demonstrated through in situ high-temperature experiments, which suggest possible enhanced energy transfer efficiency at high temperatures.