Controllable crystal form transformation and luminescence properties of up-conversion luminescent material K3Sc0.5Lu0.5F6: Er3+, Yb3+ with cryolite structure.

Zhaoliang Yan,Qingfeng Guo,Feifei Huang,Lefu Mei,Pengfei Shuai,Libing Liao

doi:10.1039/d1ra06258a

Zhaoliang Yan, Qingfeng Guo + Show 4 more

Open Access

https://doi.org/10.1039/d1ra06258a

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Journal: RSC advances	Publication Date: Jan 1, 2021
Citations: 2	License type: CC BY 3.0

Affiliation: China University of Geosciences (Beijing)

Abstract

In this paper, a novel cryolite-type up-conversion luminescent material K3Sc0.5Lu0.5F6: Er3+, Yb3+ with controllable crystal form was synthesized by a high temperature solid state method. K3Sc0.5Lu0.5F6: Er3+, Yb3+ can crystallize in monoclinic or cubic form at different temperatures. The composition, structure and up-conversion luminescence (UCL) properties of K3Sc0.5Lu0.5F6: Er3+, Yb3+ samples with different crystal form were investigated in detail. It is impressive that both monoclinic and cubic forms of K3Sc0.5Lu0.5F6: Er3+, Yb3+ show green emission (2H11/2/4S3/2→4I15/2). The luminescence intensity of cubic K3Sc0.5Lu0.5F6 is much higher than that of the monoclinic form, and the reasons are also discussed in detail. The results show that the luminescence intensity of up-conversion materials can be effectively tuned by controlling the crystal form. According to the power dependent UCL intensity, the UCL mechanism and electronic transition process were discussed. In addition, the fluorescence decay curves were characterized and the thermal coupling levels (TCLs) of Er3+ (2H11/2/4S3/2 → 4I15/2) in the range of 304–574 k were used to study the optical temperature sensing characteristics. All the results show that K3Sc0.5Lu0.5F6: Er3+, Yb3+ can be used in electronic components and have potential application value in temperature sensing fields.

Highlights

Lanthanides can be excited by an external light source and the electrons of lanthanides can jump between different energy levels, showing the absorption of photons and upconversion luminescence characteristics
With the increase of Lu3+ doping concentration, the X-ray diffraction (XRD) diffraction peaks of the sample shi to lower diffraction angles. This can be explain that the Sc3+ in the lattice is replaced by a larger Lu3+, which leads to the expansion of the unit cell volume, the crystal interplanar spacing (d) becomes larger.[35,36]
Monoclinic and cubic KSLF: Er3+, Yb3+ were prepared by high temperature solid state method, a combination of XRD, SEM, TEM, XPS shows that KSLF: Er3+, Yb3+ with monoclinic (P21/n) and cubic (Fd3) systems can be mutual transformed at different temperatures

Summary

Introduction

Lanthanides are usually used as the luminescence center of upconversion luminescent materials due to their abundant energy levels, efficient energy conversion, and unique optical properties.[1,2] Lanthanides can be excited by an external light source and the electrons of lanthanides can jump between different energy levels, showing the absorption of photons and upconversion luminescence characteristics. The most common way to improve the efficiency of upconversion is to use a host with low phonon energy.[16] We hope to nd materials with suitable crystal eld environment and higher temperature sensitivity around Er3+, which can further improve the performance of optical temperature sensor. We systematically compared the chemical composition, crystal structure, micromorphology, and up-conversion luminescence properties of KSLF: Er3+, Yb3+ with different crystal forms. We discussed the possible luminescence mechanisms in the two crystal forms, the reasons for the difference in the electronic transition process and the up-conversion luminescence performance, and the application possibility of KSLF: Er3+, Yb3+ in temperature-sensitive areas

Material synthesis and characterization

Results and discussion

Conclusions