Preparation And Luminescence Properties Of Rare Earth Ions Doped Silicate Luminescent Materials

Upconversion luminescence?UCL?materials exhibit numerous desirable properties,such as narrow emission band,no-background light,and non-photo bleaching;UCL materials also received great attention because of their potential applications in display,anti-counterfeiting technology,optical storage,visible laser,optical fiber communication,and other industrial fields.Host materials show significant effect on the UCL efficiency of phosphors.Alkaline earth silicate usually exhibits stable physical and chemical properties,good anti-ultraviolet ability,and wide excitation band,which are suitable for a host material of phosphors.In this study,Ca₃Y₂Si₃O₁₂ upconversion phosphors doped with different concentrations of Er³⁺,Yb³⁺,and Tm³⁺ ions were successfully synthesized by solid-statereaction method at 1400 ?.The UCL properties of the phosphors were evaluated systematically under 1550 nm and 980 nm excitation.The major conclusions described as follows:1.Ca₃Y₂Si₃O₁₂:Er³⁺ upconversion phosphors were synthesized by solid-state reaction method at 1400 ?.The UCL properties of the phosphors are evaluated systematically under 1550 nm excitation.The phosphors exhibit two typical emission bands centered at 550 nm?green light?and 670 nm?red light?,which correspond to the ²H_11/2/⁴S_3/2?⁴I_15/2 and ⁴F_9/2?⁴I_15/2 transitions of Er³⁺ ion,respectively.The dependence of UCL intensity on excitation power proves that the observed emissions are realized by three-photon absorption.Strong red emission with high color purity is obtained under low doping condition.The intensity ratio of red and green emissions is approximately 12:1.An obvious enhancement on the green emission intensity and a reverse variation on the red emission intensity are observed with the increase in Er³⁺ concentration.This effect is attributed to the energy transfer process between Er³⁺ ion pairs.Furthermore,the ⁴I_13/2+⁴I_13/2 ? ⁴I_15/2+⁴I_9/2 and ⁴I_13/2+⁴I_9/2 ? ⁴I_15/2+²H_11/2 transition mechanisms of the phosphor doped with different contents of Er³⁺ are discussed in detail.In this manner,color-tunable and high-purity UCL from the same component phosphor can be obtained.2.Er³⁺and Yb³⁺ co-doped Ca₃Y₂Si₃O₁₂ phosphors were prepared successfully by solid-state reaction method and the influence of Yb³⁺ conditions on UCL properties of the phosphor was discussed under 980 nm excitation.The dependence of the UCL intensity on excitation power proves that the observed emissions are obtained via two absorption processes.The UCL intensity and brightness of the phosphor increased firstly and then decreased with the increasing Yb³⁺ concentration,and the optimum concentration is 30%.Furthermore,the IR/IG value remains stable at 0.68 when Yb³⁺doping concentration is higher than 20%,showing well color stability.These UCL properties are much different with those obtained from Ca₃Y₂Si₃O₁₂:Er³⁺ phosphor excited by 1550 nm excitation.3.Ca₃Y₂Si₃O₁₂:Tm³⁺,Yb³⁺ upconversion phosphors were synthesized by solid-state reaction method at 1400 and the UCL properties of the phosphor were studied under 980 nm excitation.The phosphor exhibits strong blue light?475 nm?and near infrared light?810 nm?,as well as weak red?650 nm?light,which correspond to the ¹G₄ ? ³H₆,³H₄ ? ³H₆ and ¹G₄ ? ³F₄ transitions of Tm³⁺ ion,respectively.The dependence of the UCL intensity on excitation power proves that the observed emissions are obtained via three and two absorption processes.The UCL intensity and brightness of the phosphor increased firstly and then decreased with the increasing Yb³⁺concentration,and the optimum concentration is 15%.Under the best doping condition,the intensity ratio of blue and red emissions is calculated to be 12:1,and the chromaticity coordinate of the phosphor locates at the blue region?0.1292,0.1523?.Furthermore,the brightness of the phosphor can reach 6.8 cd/m² as the exciting power density is increased to be 3.9 W/cm².These measurement results indicate that the phosphor exhibits excellent blue UCL property and application potential.