Optical properties of Eu3+/Pr3+ doped Zn4O(BO2)6 synthesized by solid-state reaction

Zn₄O(BO₂)₆ based on the [B₂₄O₄₈] sodalite-cage structure fixed by the inside [Zn₄O₁₃] clusters is expected to be a new class of solid-state lighting material with perfect thermal and mechanical stability. Herein, in the current work, we have respectively introduced non-equivalent rare-earth cations Eu³⁺ and Pr³⁺ into Zn₄O(BO₂)₆ host to design white and green emission materials by a novel solid-phase sintering method at lower temperatures. Zn₂B₆O₁₁ replacing B₂O₃ or H₃BO₃ as raw materials can effectively avoid the impure products caused by the uncontrollable volatilization of B₂O₃ or H₃BO_3. The newly designed light-emitting materials of Zn_4(1-x)O(BO₂)₆: xRe³⁺ (ReEu or Pr), including Zn₄O(BO₂)₆ host, have good absorption capacity in the ultraviolet region. Under ultraviolet irradiation, Zn₄O(BO₂)₆, Zn_4(1-x)O(BO₂)₆: xEu³⁺and Zn_4(1-x)O(BO₂)₆: xPr³⁺ emit the blue, white and green lights, respectively. In addition, all these materials can effectively degrade methylene blue, in which Zn_4(1-x)O(BO₂)₆: xPr³⁺ has the highest efficiency. The luminescence and degradation mechanisms of Zn₄O(BO₂)₆, Zn_4(1-x)O(BO₂)₆: xEu³⁺and Zn_4(1-x)O(BO₂)₆: xPr³⁺ have been adequately explained by their electronic structures based on the first principle calculations. The current study confirms that the doping of Eu³⁺/Pr³⁺ in Zn₄O(BO₂)₆ can broaden its applications as photoluminescent and photocatalytic materials.