First-Principles Study on Self-Activated Luminescence and 4f -> 5d Transitions of Ce3+ in M-5(PO4)(3)X (M = Sr, Ba; X = Cl, Br)
First-Principles Study on Self-Activated Luminescence and 4f -> 5d Transitions of Ce3+ in M-5(PO4)(3)X (M = Sr, Ba; X = Cl, Br)
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M-5(PO4)(3)X (M = Sr, Ba; X = Cl, Br) 中 Ce3 自激活发光和 4f -> 5d 跃迁的第一性原理研究
DOI：
10.1021/acs.inorgchem.0c00406
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发表时间：
2020
影响因子：
4.6
通讯作者：
Yin Min
中科院分区：
文献类型：
--
作者：
Wen Jun;Wang Yan;Jiang Guisheng;Zhong Jiyou;Chu Jimin;Xia Qangsheng;Zhang Qingping;Ning Lixin;Duan Chang-Kui;Yin Min
利用标准的PBE0混合泛函，结合基于波函数的嵌入式簇初始计算（在CASSCF/CASPT2/ rasi - so水平），从第一原理方法结合混合密度泛函理论（DFT）计算，确定了磷灰石型M5(PO4)3X （MPOX; M = Sr或Ba； X = Cl或Br）样品中自激活发光的起源和掺杂铈的Sr5(PO4)3Cl （SPOC）荧光粉的光谱分配。通过电子结构计算，精确地推导出基体的带隙、原生缺陷和掺杂Ce3+离子在能带中的杂质态位置，以及共价掺杂的电荷补偿机制。在O-poor条件下缺陷形成能的计算表明，在还原气氛下制备的未掺杂MPOX样品容易产生天然缺陷，由此推导出热力学和光学跃迁能级以及相应的能量，从而解释了之前报道的未掺杂MPOX的发光机理。我们的计算表明，自激活发光主要归因于与氧空位（VO）结合的激子的光学跃迁，以及它们的电荷态0↔1+的变换。此外，根据初始计算的Ce3+离子在宿主体Sr(1)和Sr(2)位点的4f1→5d1 - 5跃迁的能量和相对振荡强度，成功地分配了SPOC: Ce3+， Na+荧光粉同步辐射激发光谱中观察到的8个激发带。希望应用本工作中可行的第一性原理方法，探索未掺杂和镧系掺杂荧光粉的发光起源，从化学成分和材料微观结构的角度对实验进行补充。
The origin of the self-activated luminescence in the apatite-type M5(PO4)3X (MPOX; M = Sr or Ba; X = Cl or Br) samples and the spectral assignment for cerium-doped Sr5(PO4)3Cl (SPOC) phosphors are determined from first-principles methods combined with hybrid density functional theory (DFT) calculations, using the standard PBE0 hybrid functional, with wave function-based embedded-clusterab initiocalculations (at the CASSCF/CASPT2/RASSI–SO level). Electronic structure calculations are performed in order to accurately derive the band gaps of the hosts, the locations of impurity states in the energy bands that are caused by native defects and doped Ce3+ions, and the charge-compensation mechanisms of aliovalent doping. The calculations of defect formation energies under O-poor conditions demonstrate that the native defects are easily generated in the undoped MPOX samples prepared under reducing atmospheres, from which thermodynamic and optical transition energy levels, as well as the corresponding energies, are derived in order to interpret the luminescence mechanisms of the undoped MPOX as previously reported. Our calculations reveal that the self-activated luminescence is mainly attributed to the optical transitions of the excitons bound to the oxygen vacancies (VO), along with their transformation of the charge states 0 ↔ 1+. Furthermore, the eight excitation bands observed in the synchrotron radiation excitation spectra of SPOC: Ce3+, Na+phosphors are successfully assigned according to theab initiocalculated energies and relative oscillator strengths of the 4f1→ 5d1–5transitions for the Ce3+ions at both the Sr(1) and Sr(2) sites in the host. It is hoped that the feasible first-principles approaches in this work are applied in order to explore the origins of the luminescence in undoped and lanthanide-doped phosphors, complementing the experiments from the perspective of chemical compositions and the microstructures of materials.