Luminescence and energy transfer phenomena in YVO₄ single crystal co-doped with Tm³⁺ and Eu³⁺

Detailed spectroscopic investigation of YVO₄:5 at% Eu³⁺, 1 at % Tm³⁺ single crystal encompassing analysis of absorption, excitation and time resolved emission spectra recorded at 5 K and 300 K made it possible to determine energies, intensities and bandwidths of transitions within 4fⁿ configurations of trivalent thulium and europium. Transients recorded upon femtosecond pulse excitation made it possible to determine dynamics of population build-up and relaxation of excited states involved in luminescence phenomena. It was found that in YVO₄:Eu, Tm system the metastable ⁵D₀ level of Eu³⁺ and ¹G₄ level of Tm³⁺ can be populated by energy transfer from excited VO₄³⁻ group and respective intra-ion relaxation processes from higher energy levels. Recorded excitation spectra of the ⁵D₀ luminescence of Eu³⁺ and of the ¹G₄ luminescence of Tm³⁺ do not evidence the Eu³⁺↔Tm³⁺ energy transfer. Nevertheless, an examination of acquired luminescence decay curves, performed with reference to available information on relaxation dynamics of YVO₄:Tm³⁺ system, reveals that the incorporation of Eu³⁺ accelerates decays of the ¹G₄ and ³H₄ levels of Tm³⁺. Spectroscopic parameters characterising the donor–acceptor interaction involved in the ³H₄ decay were evaluated applying the Inokuti–Hirayama model. Relevance of donor and acceptor transition peculiarities for energy transfer processes contributing to the ¹G₄ and ³H₄ decays was assessed in the framework of phenomenological model proposed by Kushida and discussed. It was concluded that the intensity ratio of the blue ¹G₄ luminescence to orange–red ⁵D₀ luminescence; hence the colour of visible emission in UV-excited YVO₄:Eu³⁺, Tm³⁺ phosphor, may be adjusted by appropriate choice of Eu³⁺ and Tm³⁺ concentrations. - Highlights: • Energy transfer between Tm³⁺ and Eu³⁺ and visible emission in YVO₄:Tm³⁺, Eu³⁺ system