采用CS2硫化法制备γ-La2S3时,通过掺入Eu离子,使γ-La2S3的生成温度降低500℃以上,在700℃就能得到稳定的γ-La2S3。掺入的Eu离子,充当γ-La2S3成核的晶种,从而降低γ-La2S3的生成温度。一部分Eu2＋通过不等价取代La3＋,同时在晶格中形成S空位以保持电中性;另一部分Eu2＋则填入γ-La2S3的S4四面体空洞,从而稳定了γ-La2S3的晶体结构,使其能够在1100℃下仍能保持稳定。在硫化反应过程中,Eu的掺杂使相变过程发生变化,La2S3不再经过β→γ相变,而直接由介稳相LaS2转变为γ-La2S3。光谱分析表明,在244nm紫外光激发下,掺Eu的γ-La2S3在280、390以及570nm处有3个发射带,且390nm发射峰非常强,可能源于缺陷发光,而Eu2＋的发光很弱或不发光。
The CS2 sulfurization method was adopted to synthesize Eu doped γ-La2 S3. The addition of Eu reduces the synthesis temperature with about 500℃ and stabile γ-La2S3 can be obtained at 700℃. The added Eu2+ acts as the seeds to facilitate the formation of the γ-La2S3 phase at quite low temperature. Parts of added divalent Eu2+ ions replace trivalent rare earth La3+ ions and S vacancies are left as charge compensation. In the mean- time, the rest Eu2+ ions can be inserted into the empty tetrahedral S4 cavities to fix the structure of γ-La2 S3 and stabilize the γ-La2S3 phase at temperature of 1100℃. During the reaction process, the doped Eu ion directly make metastable LaS2 phase transform to γ-La2 S3 at rather low temperature without the β→γ phase transforma- tion. Excited by 244nm, γ-La2S3 : Eu exhibits three emission band centered at 280, 390 and 570nm, respective- ly. The strong 390nm peak was probably originated from the defect emission and the Eu2+ emission was very weak or no luminescence at all.
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