Two new multinary chalcogenides with (Se2)2− dimers: Ba8Hf2Se11(Se2) and Ba9Hf3Se14(Se2)
Two new multinary chalcogenides with (Se2)2− dimers: Ba8Hf2Se11(Se2) and Ba9Hf3Se14(Se2)
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DOI：
10.1016/j.jssc.2023.124376
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发表时间：
2023-10
影响因子：
3.3
通讯作者：
Subhendu Jana;Eric A. Gabilondo;Paul A. Maggard
中科院分区：
文献类型：
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作者：
Subhendu Jana;Eric A. Gabilondo;Paul A. Maggard
用高温合成技术合成了Ba8Hf2Se 11(Se 2)和Ba9Hf3Se 14(Se 2)两种结构类型前所未有的多元硒化合物，它们是BaHf Se系中的第一个已知化合物。用单晶X射线衍射法测定了它们的结构。Ba8 Hf2 Se 11(Se 2)化合物为单斜晶系C2/c空间群，a=12.3962(15)ä，b=12.8928(15)ä，c=18.1768(17)ä，β=90.685(4)°；Ba9 Hf3 Se 14(Se 2)形成三方晶系R3‾空间群，a=b=19.4907(6)ä，c=23.6407(11)ä。这两种结构都具有准零维结构，同原子Se-Se键以(Se2)2−的形式存在，距离为2.400-2.402ó。Ba8Hf2Se11(Se2)的结构由[Hf2Se11]14−、Ba2+和(Se2)2−二聚体组成。相反，Ba9Hf3Se14(Se2)结构中含有一个新的钙钛矿型簇合物，它由8个八面体配位的Hf阳离子组成，即[Hf8Se36]40−，并孤立的[HfSe6]8个−单元被(Se2)2−二聚体和Ba2+阳离子隔开。采用两步固相合成法在1073K下合成了Ba8Hf2Se 11(Se 2)多晶，其中有少量的第二相。Ba8Hf2Se11(Se2)多晶样品的直接禁带宽度为2.2(2)eV，与其黄色相一致。密度泛函理论计算表明，它们的带隙跃迁分别源于价带(Vb)和导带(CB)边缘的主要填充Se-4p到空的Hf-5d。光吸收系数较大，在约-gt；2.0 eV处超过∼10 5 cm−1，有效质量从Ba8 Hf2 Se 11(Se 2)中的∼0.5m(Γ→A)到Ba9 Hf3 Se 14(Se 2)中的∼1.0m e(Γ→L)。因此，它们的光电性能被证明是与现有的钙钛矿型硫系化合物相竞争的，这一直是最近研究的焦点。
Abstract Two multinary selenides, Ba 8 Hf 2 Se 11 (Se 2) and Ba 9 Hf 3 Se 14 (Se 2), with unprecedented structure types have been prepared using high-temperature synthesis techniques and represent the first known compounds in the Ba-Hf-Se system. Their structures were determined from single crystal X-ray diffraction (XRD) data. The Ba 8 Hf 2 Se 11 (Se 2) compound crystallizes in the monoclinic C2/c space group with a= 12.3962 (15) Å, b= 12.8928 (15) Å, c= 18.1768 (17) Å, and β= 90.685 (4)°, while Ba 9 Hf 3 Se 14 (Se 2) forms in the rhombohedral R 3‾ space group with a= b= 19.4907 (6) Å and c= 23.6407 (11) Å. Both have pseudo-zero-dimensional structures with homoatomic Se–Se bonding in the form of (Se 2) 2− at distances of 2.400–2.402 Å. The structure of Ba 8 Hf 2 Se 11 (Se 2) is comprised of [Hf 2 Se 11] 14−, Ba 2+, and (Se 2) 2− dimers. Conversely, the Ba 9 Hf 3 Se 14 (Se 2) structure contains a novel perovskite-type cluster constructed from eight octahedrally-coordinated Hf cations, ie,[Hf 8 Se 36] 40−, and isolated [HfSe 6] 8− units which are separated by (Se 2) 2− dimers and Ba 2+ cations. Polycrystalline Ba 8 Hf 2 Se 11 (Se 2) is synthesized at 1073 K using a two-step solid-state synthesis method, with the co-formation of a small amount of a BaSe secondary phase. A direct bandgap of 2.2 (2) eV is obtained for the polycrystalline sample of Ba 8 Hf 2 Se 11 (Se 2), which is consistent with its yellow color. Density functional theory calculations reveal their bandgap transitions stem from predominantly filled Se-4p to empty Hf-5d at the edges of the valence bands (VB) and conduction bands (CB), respectively. The optical absorption coefficients are calculated to be relatively large, exceeding∼ 10 5 cm− 1 at about> 2.0 eV with effective masses in the CB varying from∼ 0.5 m e (Γ→ A) in Ba 8 Hf 2 Se 11 (Se 2) to∼ 1.0 m e (Γ→ L) in Ba 9 Hf 3 Se 14 (Se 2). Thus, their optoelectronic properties are shown to be competitive with existing perovskite-type chalcogenides that have been a focus of recent research efforts.