Processing-Dependent Microstructure of AgCl–CsAgCl2 Eutectic Photonic Crystals

Jaewon Choi, Ashish A. Kulkarni, Erik Hanson, Daniel Bacon-Brown, Katsuyo Thornton, Paul V. Braun

Research output: Contribution to journalArticlepeer-review

Abstract

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–CsAgCl2 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.

Original languageEnglish (US)
Article number1701316
JournalAdvanced Optical Materials
Volume6
Issue number14
DOIs
StatePublished - Jul 18 2018

Keywords

  • directional solidification
  • eutectics
  • microstructure transition
  • photonic crystals
  • self-organized

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Atomic and Molecular Physics, and Optics

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