Phase Transition and Second Harmonic Generation in Thiophosphates Ag2Cd(P2S6) and AgCd3(PS4)S2 Containing Two Second-Order Jahn–Teller Distorted Cations

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• 作者：Yu-Hang Fan ; Xiao-Ming Jiang ; Bin-Wen Liu ; Shu-Fang Li ; Wei-Huan Guo ; Hui-Yi Zeng ; Guo-Cong GuoJin-Shun Huang
• 刊名：Inorganic Chemistry
• 出版年：2017
• 出版时间：January 3, 2017
• 年：2017
• 卷：56
• 期：1
• 页码：114-124
• 全文大小：817K
• ISSN：1520-510X

文摘

Two new phases in the Ag–Cd–P–S system containing two second-order Jahn–Teller (SOJT) distorted d¹⁰ cations (Cd²⁺ and Ag⁺), namely, Ag₂Cd(P₂S₆) (1) and AgCd₃(PS₄)S₂ (2), are obtained via medium-temperature solid-state synthesis. Compound 1 exhibits a two-dimensional layered structure and undergoes a first-order structural phase transition at approximately 280 °C. This outcome can be ascribed to the significant mismatch in the expansion coefficients between Cd–S (Ag–S) and P–P (P–S) bonds evaluated through bond valence theory. The three-dimensional non-centrosymmetric (NCS) framework of 2 is constructed by two types of tetrahedral layers consisting of corner-shared CdS₄, AgS₄, and PS₄ tetrahedra. Compound 2 exhibits second harmonic generation (SHG) intensity of 0.45 times that of commercial AgGaS₂ (AGS) at a laser irradiation of 1.85 μm and an optical band gap of 2.56 eV, and no intrinsic vibrational absorption of chemical bonds is observed in the range of 2.5–18.2 μm. Both phase transition in 1 and SHG properties in 2 are closely related to the SOJT distorted d¹⁰ cations and diverse phosphorus–sulfur polyanions (P_aS_b)ⁿ⁻, which together can easily result in NCS distorted structures and interesting properties.