Abstract Single crystals of novel mixed alkali rare-earth orthoborates K3Li3Dy7(BO3)9 and K3Li3Tb7(BO3)9 were obtained by spontaneous crystallization from high temperature flux. The structure determination from single crystal X-ray diffraction relevels that K3Li3Dy7(BO3)9 and K3Li3Tb7(BO3)9 crystallize into the non-centrosymmetric orthorhombic space group Pca21 with the lattice parameters of a = 20.8225(5) A, b = 6.4118(2) A, c = 17.4976(4) A, Z = 4 and a = 20.9218(9) A, b = 6.4420(3) A, 17.5285(8) A, Z = 4, respectively. Their condensed three-dimensional networks feature infinite triangle-wave chains composed of [RE5O32] polyhedral pentamers, which are further connected by RE2O14 dimmer and isolated BO3 planar groups. K+ and Li+ cations are situated in interstitial voids in-between these chains. The UV–Vis diffuse spectra of K3Li3Dy7(BO3)9 and K3Li3Tb7(BO3)9 show the typical Dy3+ and Tb3+ absorption bands arising from their unpaired 4f electrons. Large bandgaps of these two rare-earth borates for both direct and indirect optical transition were determined using Tauc plots. Excited by the ultraviolet light, K3Li3Dy7(BO3)9 and K3Li3Tb7(BO3)9 were observed to emit the strong bule and green luminescence, respectively. In addition, polycrystalline of Ho-, Er- and Sm-analogues were synthesized via solid-state reaction. The lattice parameters of whole members, determined by Rietveld refinement, are found to obey the lanthanide contraction.

中文翻译：

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两种新型非中心对称混合碱金属原硼酸盐的合成、结构测定和表征：K3Li3RE7(BO3)9 (RE=Dy, Tb)

摘要 通过高温熔剂自发结晶获得了新型混合碱稀土原硼酸盐K3Li3Dy7(BO3)9和K3Li3Tb7(BO3)9单晶。单晶X射线衍射结构确定K3Li3Dy7(BO3)9和K3Li3Tb7(BO3)9结晶成非中心对称正交空间群Pca21，晶格参数a = 20.8225(5) A, b = 6.4118( 2) A, c = 17.4976(4) A, Z = 4 和 a = 20.9218(9) A, b = 6.4420(3) A, 17.5285(8) A, Z = 4。他们凝聚的三维网络具有无限三角波链，由 [RE5O32] 多面体五聚体组成，通过 RE2O14 调光器和孤立的 BO3 平面基团进一步连接。K+ 和 Li+ 阳离子位于这些链之间的间隙空隙中。K3Li3Dy7(BO3)9 和 K3Li3Tb7(BO3)9 的 UV-Vis 漫射光谱显示了典型的 Dy3+ 和 Tb3+ 吸收带，这些吸收带由它们的未配对 4f 电子产生。使用 Tauc 图确定这两种稀土硼酸盐的直接和间接光学跃迁的大带隙。在紫外光激发下，K3Li3Dy7(BO3)9和K3Li3Tb7(BO3)9分别发出强蓝光和绿光。此外，通过固态反应合成了Ho-、Er-和Sm-类似物的多晶。发现由 Rietveld 细化确定的整个成员的晶格参数服从镧系收缩。使用 Tauc 图确定这两种稀土硼酸盐的直接和间接光学跃迁的大带隙。在紫外光激发下，K3Li3Dy7(BO3)9和K3Li3Tb7(BO3)9分别发出强蓝光和绿光。此外，通过固态反应合成了Ho-、Er-和Sm-类似物的多晶。发现由 Rietveld 细化确定的整个成员的晶格参数服从镧系收缩。使用 Tauc 图确定这两种稀土硼酸盐的直接和间接光学跃迁的大带隙。在紫外光激发下，K3Li3Dy7(BO3)9和K3Li3Tb7(BO3)9分别发出强蓝光和绿光。此外，通过固态反应合成了Ho-、Er-和Sm-类似物的多晶。发现由 Rietveld 细化确定的整个成员的晶格参数服从镧系收缩。