Abstract

This work reports the effects of two reducing atmospheres (N₂ + H₂ and carbon) on the luminescent, morphological, and structural properties of Sr₄Al₁₄O₂₅:Eu²⁺ (1 mol%), Dy³⁺ (2 mol%), Cr³⁺ (1–4 mol%) [SALO:Eu, Dy, Cr] phosphors. They were synthesized by a combustion method followed by an annealing treatment in a reducing atmosphere. According to scanning electron microscopy (SEM) images, the samples annealed in both types of reducing atmospheres present microparticles with irregular shape. An increase of Cr concentration from 1 to 4 mol% produced microparticles with higher porosity. X-ray diffraction patterns demonstrated that the orthorhombic phase was maintained in all the samples synthesized with different Cr concentrations or reducing atmospheres. Two main emission bands centered at 490 and 693 nm were observed in the SALO:Eu, Dy, Cr phosphors under excitation at 375 nm. In general, the annealing under carbon atmosphere produced the strongest luminescent emission and the longest phosphorescence times in SALO:Eu, Dy, Cr phosphors. When the Cr concentration is increased from 1 to 4 mol%, the phosphorescence times for the NIR and VIS bands were drastically reduced from ≈1830 to 40–60 s. The phosphorescence intensity was favored by the presence of defects such as oxygen vacancies (Vo) and Dy³⁺–Vo traps, which were formed after the introduction of Dy³⁺ and Cr³⁺ ions in the SALO host. The presence of these defects was confirmed by absorbance measurements. The annealing in carbon atmosphere is simpler than that in H₂ + N₂ atmosphere and leads to enhanced luminescent properties of SALO:Eu, Dy, Cr phosphors.

中文翻译：

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还原气氛对Sr 4 Al 14 O 25：Eu 2+，Dy 3+，Cr 3+荧光粉的光致发光和磷光性能的影响

摘要

这项工作报告了两种还原气氛（N ₂  + H ₂和碳）对Sr ₄ Al ₁₄ O ₂₅：Eu ²⁺（1 mol％），Dy ³⁺（2 mol ）的发光，形态和结构性质的影响％），Cr ³⁺（1-4 mol％）[SALO：Eu，Dy，Cr]荧光粉。它们通过燃烧方法合成，然后在还原气氛中进行退火处理。根据扫描电子显微镜（SEM）图像，在两种类型的还原气氛中退火的样品均呈现不规则形状的微粒。Cr浓度从1摩尔％增加到4摩尔％产生具有更高孔隙率的微粒。X射线衍射图谱表明，在不同的Cr浓度或还原气氛下合成的所有样品中均保持了正交晶相。在375nm激发下的SALO：Eu，Dy，Cr磷光体中观察到两个主要在490和693nm处的主要发射带。通常，碳气氛下的退火在SALO中产生最强的发光和最长的磷光时间：Eu，Dy，铬磷光体。当Cr的浓度从1 mol％增加到4 mol％时，NIR和VIS波段的磷光时间从≈1830s减少到40-60 s。磷空缺（Vo）和Dy等缺陷的存在有利于磷光强度³⁺ -Vo陷阱，是在SALO主体中引入Dy ³⁺和Cr ³⁺离子后形成的。这些缺陷的存在通过吸光度测量确认。碳气氛中的退火比H ₂  + N ₂气氛中的退火更简单，并导致SALO：Eu，Dy，Cr磷光体的发光性能增强。