Effect of alkali metal ions introduction on the fluorescence properties of Er-Tm-Yb synergistically sensitized phosphors

[Display omitted] •The enhancement mechanism of Tm3+ ions as intrinsic luminescence centers and transient energy trapping centers for the transition luminescence at 1550 nm has been investigated.•The enhancement mechanism of the conversion luminescence at 1550 nm by Yb3+ ions as mutual sensing ions and reverse energy transfer centers was investigated.•The equilibrium relationship between quenching and enhancement of the intensity of the conversion luminescence on the samples by the introduction of alkali metal ions has been investigated. Upconversion fluoride phosphors Na1-xMxY1-a-b-cF4:Er3+a, Tm3+b, Yb3+c (M = Li+/K+) have been synthesized by low-temperature combustion method. The optimal doping ratios of ions in the matrix lattice were determined by orthogonal experiments with the control variable method. It was found that when a certain amount of Tm3+ ions were doped into the lattice of Er3+ ions, the upconversion fluorescence intensity and red-to-green ratio of the samples were significantly enhanced. When a small amount of Yb3+ ions was introduced into the Er3+-Tm3 + ions co-doped samples, the upconversion fluorescence intensity of the samples was continued to be enhanced, but the red-to-green ratio was slightly decreased. The mechanism of the influence of the upconversion fluorescence intensity and the red-to-green ratio of the multidoped samples with lanthanide ions was also systematically investigated. Based on the results of orthogonal experiments, the optimal component formulations were determined and alkali metal ions were further introduced. The upconversion fluorescence enhancement mechanism of the samples after the introduction of alkali metal ions was systematically investigated. In this work, the upconversion fluorescence intensity of the prepared samples was significantly enhanced by synergistic sensitization between the ions. In addition, by adjusting the red-to-green ratio of the fluorescence of the samples, a new idea is provided for the preparation of upconversion phosphors with high color purity.