Porous crystal structures obtained from directionally solidified eutectic precursors

• Published in: Journal of crystal growth Vol. 300; no. 2; pp. 387 - 393
• Main Authors: Larrea, A., Orera, V.M.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 15.03.2007; Elsevier
• Subjects: A1. Eutectics; A1. Porous crystals; A2. Bridgman technique; B1. BaF 2; B1. CaF 2; B1. NaMgF 3; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Growth from melts; zone melting and refining; Materials science; Methods of crystal growth; physics of crystal growth; Phase diagrams and microstructures developed by solidification and solid-solid phase transformations; Physics; Solidification; 81.05.Rm; A2. Bridgman technique; B1. NaMgF 3; A1. Eutectics; A1. Porous crystals; B1. CaF 2; 81.10.Fq; B1. BaF 2; Crystal growth; 81.05.Rm; 81.10.Fq; Inorganic compounds; Directional solidification; Growth rate; Porous materials; Calcium fluorides; Precursor; A1. Eutectics; A1. Porous crystals; A2. Bridgman technique; Bl. BaF2; Bl. CaF2; Bl. NaMgF3; Pore size; Barium fluorides; Growth mechanism; Eutectic alloys; Size control; Microstructure; Crystal growth from melts; Crystal structure
• ISSN: 0022-0248; 1873-5002
• DOI: 10.1016/j.jcrysgro.2006.12.060

Interconnecting cage-like porous structures of several halide compounds were prepared by the selective leaching of one eutectic phase method. The binary eutectic precursors were prepared by directional solidification using the Bridgman crystal growth technique. Porous NaMgF 3 (40% pore volume), CaF 2 (57% pore volume) and BaF 2 (43% pore volume) crystals were obtained after water leaching the NaF component of the directionally solidified NaF/NaMgF 3, NaF/CaF 2 and NaF/BaF 2 eutectics with the appropriate entangled microstructure. The growth conditions for eutectic-coupled growth and the morphology of the eutectics have been determined. In the coupled growth regime, the size of the eutectic phases “ λ” is fairly uniform and varies with the eutectic growth rate “ v ” as λ 2 v = constant , which allows us to control the pore size within the 0.5–10 μm range. The simplicity and versatility of the eutectic growth also allows us to fabricate highly aligned porous structures at relatively high production rates.