Transient Liquid Phase Sintering and Joining of Lanthanum Calcium Ferrite

Author

Patrick G. Callahan, Boise State UniversityFollow

Publication Date

4-2008

Type of Culminating Activity

Thesis

Degree Title

Master of Science in Materials Science and Engineering

Department

Materials Science and Engineering

Supervisory Committee Chair

Darryl P. Butt

Abstract

Lanthanum calcium ferrite (La_1-xCa_xFeO₃) is a perovskite-type oxide that is used as an oxygen separation membrane and in Syngas production, processes which require them to operate in environments with high temperatures and pressures. A novel transient liquid phase (TLP) method has been applied to sintering and joining La_1-xCa_xFeO₃. The sintering behavior of cold pressed pellets with compositions La_0.9Ca_0.lFeO₃ and La_0.75Ca_0.25FeO₃ was studied using an isothermal method at temperatures up to 1400°C. Sintering had three distinct regions which were dependant on the density that had been achieved. The rate limiting mechanism for sintering was particle rearrangement in the presence of a liquid phase until approximately 65-70% theoretical density was reached. From approximately 65-90% theoretical density, sintering was rate limited by a combination of particle rearrangement in the presence of a liquid phase and solution reprecipitation. After approximately 90% theoretical density was reached, sintering was rate limited by solution reprecipitation. For La_0.9Ca_0.lFeO₃ the apparent activation energy for sintering controlled by particle rearrangement in the presence of a liquid phase was 200±50 kJ/mol. The apparent activation energy for solution reprecipitation was 700±180 kJ/mol. For La_0.75Ca_0.25FeO₃the apparent activation energy for sintering controlled by particle rearrangement in the presence of a liquid phase was 230±60 kJ/mol. The apparent activation energy for solution reprecipitation was 630±160 kJ/mol.

The TLP method was also used to successfully join La_0.9Ca_0.lFeO₃ to itself resulting in a single phase joint interface. The joined assemblies were characterized using scanning electron microscopy. The joint interfaces tended to contain some residual porosity after joining.

Recommended Citation

Callahan, Patrick G., "Transient Liquid Phase Sintering and Joining of Lanthanum Calcium Ferrite" (2008). Boise State University Theses and Dissertations. 539.
https://scholarworks.boisestate.edu/td/539