The role of NZP additions in plasma-sprayed YSZ: microstructure, thermal conductivity and phase stability effects
Abstract
A concept for lowering the thermal conductivity of plasma-sprayed yttria-stabilized zirconia (YSZ) was evaluated by adding a low thermal conductivity secondary phase. Ca_(0.5)Sr_(0.5)Zr_4P_6O_(24), a member of the zirconium phosphate or NZP family, was co-sprayed with YSZ using the recently patented small-particle plasma-spray process. The amount of NZP phase in the YSZ varied from 4 to 18 vol.%. Transmission electron microscopy revealed that the plasma-sprayed NZP existed as 30-50 nm size grains when sprayed with YSZ. Between 100 and 1200 degrees C, reductions in the thermal conductivity of NZP/VSZ composite coatings compared to YSZ-only coatings were traced to porosity effects. The NZP phase destabilized the t'-ZrO_2 phase of the YSZ, favoring the formation of t-ZrO_2, then m-ZrO_2, a phase with a high-thermal conductivity. Due to this phase change, a large hysteresis was observed in thermal conductivity during the initial heat-up and cool down cycles of the NZP containing samples.
Additional Information
Copyright © 1999 Elsevier. Received 14 April 1999; received in revised form 14 June 1999. The authors wish to thank Rick Marzec for fabrication of the coatings used in this study, Dr Chiou for assistance with the TEM, and Tom Easley and Luke Brewer for help in editing the final document. Also, Rama Nageswaran provided valuable insight into NZP. This work was supported by the U.S. Department of Energy, Federal Energy Technology Center, Cooperative Agreement No. DE-FC21-92MC29061, under subcontract 96-01-SR047. The thermal conductivity testing was supported by the U.S. DOE, Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Transportation Technologies, as part of the HTML User Program under contract DE-AC05-96OR22464, managed by Lockheed Martin Energy Research Corporation.Additional details
- Eprint ID
- 49403
- DOI
- 10.1016/S0921-5093(99)00468-2
- Resolver ID
- CaltechAUTHORS:20140908-181324609
- Department of Energy (DOE)
- DE-FC21-92MC29061
- Department of Energy (DOE)
- DE-AC05-96OR22464
- Created
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2014-09-09Created from EPrint's datestamp field
- Updated
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2021-11-10Created from EPrint's last_modified field