Microwave synthesized pyrochlore zirconates plasma spray powders

3^rd International Conference and Expo on Ceramics and Composite Materials

June 26-27, 2017 Madrid, Spain

Kirti Teja and Parvati Ramaswamy

Christ University, India

Posters & Accepted Abstracts: J Material Sci Eng

Abstract :

Pyrochlore-type rare earth zirconium oxide system (Re2Zr2O7, Re=rare earths such as La, Gd and Yb etc.) are potential candidates for thermal barrier coatings (TBCs), high-permittivity dielectrics and solid electrolytes in high-temperature fuel cells etc. Some of its favorable characteristics to suit these applications are low thermal conductivity, high temperature phase stability (no phase transformation at high temperatures), low sintering rates at elevated temperatures and suitable coefficient of thermal expansion etc. For applications involving TBCs, the goal is to develop pyrochlore oxide based coatings which promise improved high temperature properties (>1200oC), much better than the currently popular Yttria Stabilized Zirconia (YSZ) TBCs. These TBCs are expected to allow increased gas turbine efficiencies that will protect the underlying metallic components from higher operating temperatures. This work is focused on preparing pyrochlore zirconates TBCs via microwave synthesis and evaluated for performance at high temperatures (1200oC�1500oC). Homogenous Pyrochlore zirconate compositions were synthesized via microwave sintering treatment of mixed and ground raw material powders at >15000C. Evaluated for phase composition such as stabilized zirconia or zirconates by employing X-Ray Diffractometry (XRD) the synthesized powders compacts were characterized for thermal conductivity that forms the primary criteria to serve as thermal barrier coatings (TBCs). Powders from selected few favorable compositions were further synthesized via spray drying to form plasma spray powders. TBCs prepared from the spray dried compositions were characterized for adhesion, thermal fatigue (shock cycling up to 1500oC and ambient), structural phase stability, interface and oxidation characteristics, microstructure, and suitability of service at high temperature without degradation in phase or spallation. Detailed oxidation stability characteristics study involved Electron Probe Micro Analysis (EPMA) across the coating-bond coat-substrate interface in metallographic cross-sections prepared from the TBC compositions which exhibited potentiality for long duration service under harsh environmental conditions. The coatings that have been prepared exhibited favorable characteristics to perform as TBCs superior to the conventionally prepared Yttria stabilized zirconia TBCs. The results and discussion pertaining to the superior TBCs are presented in this study.

Biography :

Email: kirti.teja@christuniversity.in