K₃La（PO₄）₂基质中Tb³⁺的发光和能量传递

Tb³⁺-doped K₃La（PO₄）₂ phosphors with monoclinic structure have been prepared via a high-temperature solid-state reaction method. The phase purity of samples is checked with X-ray diffraction （XRD） technique and the Rietveld refinement is performed using XRD data of the host compound. The temperature- and concentration- dependent luminescence properties of Tb³⁺-doped samples are further studied with spectral and decay measurements. Upon 373 nm excitation， Tb³⁺-doped K₃La（PO₄）₂ phosphors display ⁵D₃-⁷F_J（J=5， 4， 3， 2） and ⁵D₄-⁷F_J′（J′=6， 5， 4， 3） transitions at room temperature（RT）. Temperature-dependent photoluminescence（PL） measurements for the sample with low Tb³⁺ doping concentration indicate that multi-phonon relaxation（MPR） has limited contribution to the quenching of ⁵D₃ emission. As Tb³⁺ concentration increases， the emission of ⁵D₄ is gradually enhanced while that of ⁵D₃ weakened， leading to the color tunability from cyan to green， which is mainly due to the cross-relaxation（CR） among Tb³⁺ ions. The decay curves of ⁵D₃ emission are further analyzed and fitted with Inokuti-Hirayama and generalized Yokota-Tanimoto models， manifesting that the main interaction type in CR process is electric dipole-quadrupole（EDQ） coupling with critical interaction distance of ~1.03 nm.