Laser processed protonic ceramics

• Published in: Journal of the European Ceramic Society 2008-08, Vol.28 (12), p.2433-2440
• Main Authors: Dynys, F.W., Berger, M.H., Sayir, A.
• Format: Article
• Language: English
• Subjects: Applied sciences; Building materials. Ceramics. Glasses; Ceramic industries; Ceramics; Chemical industry and chemicals; Condensed Matter; Directional solidification; Electrotechnical and electronic ceramics; Exact sciences and technology; Laser; Materials Science; Physics; Protonic; Technical ceramics
• ISSN: 0955-2219; 1873-619X
• DOI: 10.1016/j.jeurceramsoc.2008.03.038

High temperature protonic conductors of SrCe 0.9Y 0.1O 3− δ , Sr 3Ca 1+ x Nb 2− x O 9− δ and BaCe 0.85Y 0.15O 3− δ were fabricated by laser processing. Laser float zone method and pulse laser deposition were used to fabricate dense high temperature protonic ceramic rods and films. Melt growth processing by laser float zone produced textured microstructures with cellular characteristics. Directional solidified SrCe 0.9Y 0.1O 3− δ contained an aluminium rich inter-granular phase, whereas Sr 3Ca 1+ x Nb 2− x O 9− δ exhibits a cellular microstructure with a decreasing Ca/Nb ratio from the cell center to the cell boundary. A low Ca/Nb ratio is detrimental to proton transport. Nano-domains caused by oxygen cage tilting were observed in both compositions. Sr 3Ca 1+ x Nb 2− x O 9− δ also exhibits stoichiometric domains with an ordered distribution of Nb 5+ and Ca 2+ cations. These domains were surrounded by non-stoichiometric domains containing a random cation distribution, which preserves the global stoichiometry and charge neutrality. Electrical impedance spectroscopy revealed similar protonic transport to published data for sintered compositions. Crystalline BaCe 0.9Y 0.1O 3− δ films were fabricated on porous substrates at deposition temperatures ranging from 400 to 950 °C. Crystalline films 1–10 μm thick were deposited by excimer laser on porous Al 2O 3 and BaZrO 3 substrates. Single-phase BaCe 0.85Y 0.15O 3− δ films with a columnar growth morphology are observed with preferred crystal growth along the [1 0 0] or [0 0 1] direction. The film electrical conductivity was measured perpendicular to the film growth direction. Impedance measurements show the importance of matching crystal symmetry between substrate and film. High protonic conducting films were achieved by deposition on BaZrO 3.