Controlling the final phase of multiphase KGdF 4 materials via chemical synthesis and structural phase transition
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Controlling the final phase of multiphase KGdF4 materials via chemical synthesis and structural phase transition Jinjin Liu1
1
, Hua Yu1,*, Li Zhang1, Haotian Dong1, Shikang Liu1, and Lijuan Zhao1,*
The Key Laboratory of Weak-Light Nonlinear Photonics, Ministry of Education, School of Physics and Applied Physics Institute, Nankai University, Tianjin 300071, China
Received: 17 July 2020
ABSTRACT
Accepted: 26 August 2020
This study proposes a method for the final phase control of KGdF4 crystals for the first time, based on a chemical synthesis and structural phase transition process with increased temperature. X-ray diffraction and high-resolution transmission electron microscopy were employed to characterize the resulting structures and reveal phase transition trends. Subsequently, a theoretical phase transition model was constructed. This model indicated that final products are obtained through a combination of chemical synthesis and structural phase transition. Furthermore, it was observed that the chemical synthesis process dominates the low-temperature region, whereas the structural phase transition process dominates the high-energy region because of the additional extra energy. Finally, the density of states was theoretically calculated using the firstprinciple theory, shedding light on the structural phase transition process. This study, therefore, provides a potentially controllable method for the synthesis of desired KGdF4 crystal phases.
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Springer Science+Business
Media, LLC, part of Springer Nature 2020
1 Introduction In recent times, MGdF4 (M = Li, Na, or K) inorganic fluoride matrix materials have attracted significant attention for their excellent optical and magnetic properties [1–3]. Moreover, optical MGdF4 inorganic fluorides, which possess low phonon energies, can reduce energy loss during energy transfer processes [4, 5]. Additionally, because these materials are matrix-doped rare earth ions, they can achieve up-
and down-conversion emissions [6–11]. In terms of magnetism, Gd3? ions have a large magnetic moment and electron relaxation time on the nanosecond timescale [12]. Therefore, such ions have a wide range of potential applications, such as plasma display screens, medical diagnoses, and biological probes [13–17]. KGdF4 crystals are one of the representative MGdF4 materials. Generally, such crystals exhibit two types of structures cubic (C) and orthorhombic
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https://doi.org/10.1007/s10854-020-04360-0
J Mater Sci: Mater Electron
(O) [4, 16]. Additionally, they exhibit a trigonal phase (T), which is formed by trigonal KYF4 [18]. Numerous studies have indicated that the structures of the crystal have significant influence on their luminescence properties [19, 20]. When multiphase crystals with different crystal phases are fabricated, their luminescence efficiencies and practical applications differ [18, 21]. Therefore, studying and obtaining specific crystal phases under different conditions is an indispen
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