A recently developed fast oxide ion conductor, namely lanthanum molybdenum oxide (La2Mo2O9, LAMO), was synthesized instantaneously by a citrate-nitrate auto-ignition process at a fixed citrate to nitrate ratio of 0.3 and characterized by thermal analysis, x-ray diffraction, impedance spectroscopy, and thermal expansion measurements. Crystalline LAMO has formed instantaneously during the combustion process. The signature of the order-disorder transition of stoichiometric LAMO around 570 °C was evident from differential thermal analysis, differential scanning calorimetry electrical conductivity, and thermal expansion measurements. Though the in situ x-ray measurements did not indicate any clear evidence of a phase transition, a stepwise change in the lattice parameter near the vicinity of the transition temperature was apparent thereby confirming the phase transition to be of first order in nature. The thermal expansion coefficient of LAMO was calculated to be 13.92 × 10-6/°K at 950 °C. The present method formed phase pure LAMO instantaneously and produced sintered samples with high conductivity, namely, 0.052 S/cm at 800 °C and 0.08 S/cm at 950 °C compared to LAMO prepared through various other solution routes.
Bibliographical noteFunding Information:
The authors thank the Director, Central Glass and Ceramic Research Institute (CGCRI) for permission to publish this work. S. Basu is indebted to Council of Scientific and Industrial Research (CSIR) for the award of a Research Associateship. This work was supported through the Task Force Program on “Custom Tailored Special Materials” of CSIR. Partial financial support from the Ministry of Non-Conventional Energy Source (Government of India) is acknowledged. The work at NSLS beam line X7b was supported under contract DE-AC2-98CH10086 with the United States Department of Energy (Division of Chemical Sciences). The NSLS is supported by the Divisions of Materials and Chemcial Sciences. Technical assistance from the x-ray and SEM divisions of CGCRI is also acknowledged. The authors also thank all the members of the Electroceramics Division of CGCRI for their co-operation at every stage of this work.
All Science Journal Classification (ASJC) codes
- Materials Science(all)
- Condensed Matter Physics
- Mechanics of Materials
- Mechanical Engineering