Hydrothermal synthesis of Ba3Sc2F12:Yb3+, Ln3+ (Ln = Er, Ho, Tm) crystals and their up conversion white light emission

Abstract

Ba₃Sc₂F₁₂:Yb³⁺, Ln³⁺ (Ln = Er, Ho, Tm) crystals with various morphologies have been synthesized via a one step hydrothermal route. X-ray diffraction (XRD), scanning electron microscopy (SEM), and up conversion photoluminescence (UCPL) spectra were used to characterize the samples. The influences of surfactants, pH values, and molar ratio of F⁻/Sc³⁺ on the crystal phase, size and shape of final products have been studied in detail. The aspect ratio of products increased gradually with the increase of F⁻/Sc³⁺ molar ratio. Additionally, the luminescence properties of Ba₃Sc₂F₁₂:Yb³⁺, Ln³⁺ (Ln = Er, Ho, Tm) crystals were systematically studied. The blue emission is attributed to the ¹G₄ → ³H₆ transition of Tm³⁺; the green emission can be obtained due to the ²H_11/2/⁴S_3/2 → ⁴I_15/2 transitions of Er³⁺ and the ⁵S₂/⁵F₄ → ⁵I₈ transition of Ho³⁺; the red emission comes from the ⁴F_9/2 → ⁴I_15/2 transition of Er³⁺ and the ¹G₄ → ³F₄ transition of Tm³⁺. Based on the generation of red, green, and blue emissions in the different Ln ion-doped Ba₃Sc₂F₁₂, the white light emission can be obtained by appropriately doping Yb³⁺, Er³⁺, and Tm³⁺ in the present Ba₃Sc₂F₁₂ crystals due to the color superposition principle. Here, the sample Ba₃Sc_1.5856F₁₂:0.4Yb³⁺, 0.01Er³⁺, 0.0044Tm³⁺ crystals showed suitable intensity ratio of blue, green and red (RGB) emissions resulting in bright white light with CIE-x = 0.274 and CIE-y = 0.287, which was illustrated by a photograph under excitation of 980 nm. The prepared Ba₃Sc₂F₁₂:Ln³⁺ phosphor has potential applications in the fields of three dimensional displays, back lighting and white light sources.