Phase-Change Behavior and Nonlinear Optical Second and Third Harmonic Generation of the One-Dimensional K_(1–x)Cs_xPSe₆ and Metastable β-CsPSe₆

Abstract

The APSe6 (A = K, K(1–x)Cs x , Cs) family of one-dimensional (1D) materials was studied to examine the effects of the cation size on the nonlinear optical (NLO) response. The family has high-performing NLO properties with the noncentrosymmetric parent material, KPSe6, having infinite 1D chains of 1/∞[PSe6 –]. This structure has been successfully substituted with cesium up to K0.6Cs0.4PSe6 while retaining the polar character. All compounds crystallize in the space group Pca21 and have band gaps of 2.1 eV. In situ powder X-ray diffraction experiments using synchrotron radiation were used to determine the specifics of the amorphous to crystalline behavior and the crystallization and melting kinetics of the APSe6 system. These measurements revealed a new phase, β-CsPSe6, which is metastable and crystallizes in the noncentrosymmetric tetragonal space group P 4̅21 c with a = 12.526(2) Å, c = 12.781(3) Å, V = 2005.3(6) Å3, and Z = 8. The structure is composed of 2 sets of mutually perpendicular 1/∞[PSe6 –] chains charge-balanced by Cs cations, and the band gap of β-CsPSe6 is 1.9 eV. Second harmonic generation (SHG) measurements demonstrate that substitution of Cs into KPSe6 maintains the strong NLO signal with a very high SHG coefficient (χ(2)) of ∼150 pm/V for K(1‑x)Cs x PSe6 and 30 pm/V for β-CsPSe6. Laser-induced damage threshold analysis reveals APSe6 exhibits two-photon absorption (2PA) at 1064 nm with input laser intensity greater than 1 GW/cm2 and optical damage from 2PA at ∼2 GW/cm2. The materials also exhibit strong third harmonic generation (THG) with THG coefficients (χ(3) × 105) for KPSe6, K0.6Cs0.4PSe6, α-CsPSe6, and β-CsPSe6 to be 2.6, 3.1, 1.8, and 1.1 pm2/V2, respectively.

Non‐centrosymmetric Selenides AZn4In5Se12 (A=Rb, Cs): Synthesis, Characterization and Nonlinear Optical Properties

“…A crystallographic non‐centrosymmetric (NCS) structure is the prerequisite condition of an NLO material. Over the past decades, numerous strategies have been introduced to design new NCS materials, and many MFIR NLO compounds with strong powder SHG responses have been discovered and prepared . Among them, construction of diamond‐like frameworks (DLFs) has been considered as one of the most effective methods to obtain new MFIR NLO materials with excellent properties; typical examples include BaGa 4 Q 7 (Q=S, Se), Ba 3 AGa 5 Se 10 Cl 2 (A=K‐Cs), PbGa 4 S 7 , Li 2 CdGeS 4 , and BaGa 2 MQ 6 (M=Si, Ge, Sn; Q=S, Se) …”

Conversion of CuO Nanoplates into Porous Hybrid Cu2O/Polypyrrole Nanoflakes through a Pyrrole‐Induced Reductive Transformation Reaction

“…Direct combination reaction of the rubidium analogue results in Rb 2 ZnP 2 Se 6 as the major phase with ZnSe as a second phase (Figure S6). Direct combination of the cesium analogue consistently yields β‐CsPSe 6 39 as a second phase (Figure S7).…”

Mechanistic insight of KBiQ2 (Q = S, Se) using panoramic synthesis towards synthesis-by-design

“…13 With reaction types and assembly rules, predictive power of material synthesis can be achieved, leading to intentional synthesis of targeted materials with chosen, desired properties. 25 In-situ powder X-ray diffraction has been utilized for various interests such as materials discovery 18,19,26 and mechanism elucidation 25,[27][28][29][30][31][32][33] , as well as the investigation of metathesis reactions 27,34 , self-propagating high temperature syntheses 14,25,28 , phase change 14,35 , decomposition 36 , and crystallization 14,25,28 . This approach has shown success in discovering new materials, even in systems that were previously investigated.…”

“…A promising phase space to study is in the A-Pn-Q systems, where A is an alkali metal, Pn is a pnicogen such as bismuth or antimony, and Q is a chalcogenide, 37,38 as many are reported structures and have been of interest for their thermoelectric [39][40][41][42][43][44][45] and optical 5,35,46,47 properties.…”

“…A promising phase space to study is in the A-Pn-Q systems, where A is an alkali metal, Pn is a pnictogen such as bismuth or antimony, and Q is a chalcogenide, 37,38 as many are reported structures and have been of interest for their thermoelectric [39][40][41][42][43][44][45] and optical 5,35,46,47 properties. Moreover, a number of the known compounds are isostructural disordered analogues, such as KBiS 2, NaBiS 2 , NaBiSe 2 , KBiSe 2 , and NaSbS 2 , while ordered phases contain similar structural motifs.…”