Enhancement of green emission from Ca₁₄Al₁₀Zn₆O₃₅: Tb³⁺ phosphors via cross-relaxation energy transfer by Li⁺ ions

Tb³⁺ doped Ca₁₄Al₁₀Zn₆O₃₅ phosphors were prepared by a traditional solid-state reaction approach. The Tb³⁺ doped phosphors exhibit blue and green emission under the 285 nm excitation. The green to blue emission ratio is gradually enhanced as the Tb³⁺ concentration increases, which is ascribed to the enhanced cross-relaxation energy transfer (CRET) processes between Tb³⁺ ions. Li⁺ ions were introduced to the composition as an attempt to address the charge mismatch induced by Tb³⁺ for Ca²⁺ ion substitution. An enhancement of green emission from Tb³⁺ ions is observed after co-doping with Li⁺ ions. The lifetime measurement confirms that the CRET efficiency and energy transfer rate are simultaneously increased by Li⁺ ions. The results suggest that the incorporation of Li⁺ ions is a feasible approach to overcome charge vacancy defects and enhance CRET processes.