运用密度泛函理论研究了氮掺杂对Ca2SiO4∶ Eu2+电子结构和吸收光谱的影响.研究发现:氮原子在费米面附近提供了多个态,从而使荧光粉的带隙宽度变窄,并导致N2p到Eu4f的带间能量转移.由于围绕激活中心的氮离子的作用,Eu2+受到较强的电子云重叠和晶体场影响,从而造成Eu4f和5d态的分裂. 因此,氮掺杂Ca2SiO4∶ Eu2+的吸收光谱发生了红移,在220～470 nm波长范围内吸收更强.
The electronic structure and absorption spectrum of Ca2SiO4∶ Eu2+ was studied by using density functional theory.It is found that N atoms substituted provide many states around the Femi level,which leads to narrow optical band gap and interband transition originating from N2p to the Eu4f.In the N-doped Ca2SiO4∶ Eu2+ phosphor,Eua+ ions experience a strong nephelauxetic effect and crystal field due to the coordinating nitrogen ions around the activated centers,which results in Eu4f and 5d states splitting.Thus,the red-shift of the absorption spectrum and high absorption band in the wavelength of 220-470 nm takes place for the N-doped Ca2SiO4∶ Eu2+ phosphor.
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