Sustainable synthesis of pyrochlore gadolinium zirconate through the molten salt method: A green approach

Abstract

Gadolinium zirconate (GZO) with pyrochlore phase exhibits exceptional promise for thermal barrier coatings due to its notable low thermal conductivity. Current synthesis methods for GZO, however, are frequently complex, energy-intensive, and environmentally hazardous. A more sustainable and eco-friendly synthesis route for GZO is thus imperative. This research introduces a green synthesis process for pyrochlore GZO utilizing the molten salt method.Experimental synthesis at varying temperatures revealed changes in the phase composition of GZO via the molten salt method. Fluorite GZO formed at 1200 °C, while pyrochlore GZO appeared at 1400 °C. XRD refinement, TEM, and Raman spectroscopy confirmed these results. Density Functional Theory (DFT) calculations established the minimum theoretical synthesis temperature for pyrochlore GZO at 1370 °C. Limiting factors for reactions at different temperatures during the molten salt synthesis process were identified. DFT calculations and experiments verified that the fluorite structure GZO transitions to pyrochlore GZO at temperatures exceeding 1370 °C. Property tests on pyrochlore GZO samples synthesized through two pathways showed minimal differences. This study thus lays a theoretical foundation for the eco-friendly synthesis of pyrochlore GZO material using the molten salt method and offers insights for future process development.