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Processing‐Dependent Microstructure of AgCl–CsAgCl 2 Eutectic Photonic Crystals
Author(s) -
Choi Jaewon,
Kulkarni Ashish A.,
Hanson Erik,
BaconBrown Daniel,
Thornton Katsuyo,
Braun Paul V.
Publication year - 2018
Publication title -
advanced optical materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.89
H-Index - 91
ISSN - 2195-1071
DOI - 10.1002/adom.201701316
Subject(s) - eutectic system , materials science , lamellar structure , microstructure , nucleation , directional solidification , phase (matter) , optics , refractive index , planar , composite material , optoelectronics , thermodynamics , physics , chemistry , organic chemistry , computer graphics (images) , computer science
Directional solidification of a eutectic melt allows control over the resultant eutectic microstructure, which in turn impacts both the mechanical and optical properties of the material. These self‐organized phase‐separated eutectic materials can be tuned to have periodicities from tens of micrometers down to nanometers. Furthermore, the two phases possess differences in their refractive index leading to interesting optical properties that can be tailored within the visible to infrared wavelength regime. It is found the binary salt eutectic AgCl–CsAgCl 2 system forms a rod microstructure with sample draw rates up to 0.2 mm s −1 which transitions to a lamellar microstructure at draw rates greater than 0.36 mm s −1 . Heat‐transfer simulations reveal a draw rate‐dependent direction of motion of the solidification front, which for a range of draw rates requires nucleation of the minority solid phase at the sample wall. Phase‐field modeling indicates that the initial eutectic structure at the sample boundary, either rod or lamellar, dictates the bulk eutectic morphology. These samples contain submicrometer periodicities which coupled with their optical transparency results in them exhibiting draw rate‐dependent near‐IR reflectance peaks consistent with stop bands for 2D hexagonal (rod) and 1D planar (lamellar) photonic crystals.