A Dy³⁺-doped PbGa₂S₄ crystal with low phonon energy has been proved to be able to achieve the direct lasing of a mid-infrared laser. The single-crystal growth of Dy³⁺:PbGa₂S₄ was investigated in this work. On the basic of the high-purity polycrystalline material synthesized using a pressure-assisted method, a Dy³⁺:PbGa₂S₄ single crystal with φ 21 × 50 mm³ was successfully grown using the Bridgman method with a crucible–capsule technique. To understand the cleavage character of the PbGa₂S₄ crystal and get further insight into its electronic and phonon properties, the electronic, phonon, and mechanical properties of the PbGa₂S₄ host were investigated using first-principles calculations. PbGa₂S₄ exhibits not only a large electronic energy gap (2.76 eV) but also a low phonon energy (392 cm^–1) due to the incorporation of heavy Pb atoms between the interlayers. The high-frequency phonon bands of PbGa₂S₄ are mainly contributed by the vibrations of Ga–S atoms in the layer network formed by GaS₄ units. However, the weak Pb–S bonding connecting the alternating layers results in cleavage behavior of the PbGa₂S₄ crystal. We believe that the results of this paper could provide useful references for preparing or designing new chalcogenide hosts for mid-infrared lasers.

中文翻译：

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中红外激光晶体Dy ³⁺：PbGa ₂ S _4的晶体生长和第一性原理计算

具有低声子能量的掺Dy ^3+的PbGa ₂ S ₄晶体已被证明能够实现中红外激光的直接激光发射。在这项工作中研究了Dy ³⁺：PbGa ₂ S ₄的单晶生长。在使用压力辅助法合成高纯度多晶材料的基础上，使用坩埚-胶囊技术通过Bridgman方法成功地生长了φ21 ×50 mm ³的Dy ³⁺：PbGa ₂ S ₄单晶。了解PbGa ₂ S ₄的裂解特性晶体并进一步了解其电子和声子性能，使用第一性原理计算研究了PbGa ₂ S ₄基质的电子，声子和机械性能。PbGa ₂ S ₄不仅表现出较大的电子能隙（2.76 eV），而且由于在中间层之间引入了重的Pb原子，因此具有较低的声子能（392 cm ^–1）。PbGa ₂ S ₄的高频声子带主要由GaS ₄单元形成的层网络中Ga-S原子的振动贡献。但是，连接交替层的弱Pb-S键导致PbGa _2的裂解行为S ₄晶体。我们认为，本文的结果可为制备或设计用于中红外激光的新型硫族化物基质提供有用的参考。