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Journal article
Establishing the Temperature-Dependent Synthesis Window of β-TaON by Coupling Predictive Thermodynamic Modeling with Experimental Validation
Chemistry of Materials, Forthcoming
28 Jun 2026
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Abstract
Phase-pure synthesis has been a major challenge for transition-metal oxynitrides due to their sensitivity to synthesis conditions and limited understanding of their underlying thermodynamics. Beta-phase tantalum oxynitride (β-TaON), a promising candidate for (photo)catalytic applications, is particularly difficult to reproducibly synthesize as a single-phase material at equilibrium. In this study, we developed and experimentally validated a thermodynamic model to identify optimal conditions for the single-phase synthesis of β-TaON via ammonolysis reactions. Gibbs free energies of reactant, product, and byproduct phases were predicted as a function of temperature using first-principles calculations with the quasi-harmonic approximation (QHA), as well as implemented from available thermodynamic databases. Utilizing these Gibbs energies, the calculation of phase diagrams (CALPHAD) approach was employed to develop a thermodynamic model for assessing the phase equilibria associated with the ammonolysis reactions, enabling prediction of temperature-dependent synthesis windows for β-TaON. Experimental syntheses were carried out across a range of temperatures and gas conditions, validating model predictions and iteratively refining the model accuracy through an integrated feedback loop. Co-flown gases beyond ammonia and water were also shown to be influential on β-TaON phase purity and reaction kinetics. A three-dimensional (3D) phase diagram predicted on the axes of parameters that can be controlled during practical synthesis quantitatively reveals a narrow, phase-pure synthesis window for β-TaON.
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Details
- Title
- Establishing the Temperature-Dependent Synthesis Window of β-TaON by Coupling Predictive Thermodynamic Modeling with Experimental Validation
- Creators
- Aksha Gilbert Prince - Drexel UniversityYuanchen Gao - Drexel University, Materials Science and EngineeringDmitri LaBelle - Drexel University, Materials Science and EngineeringJill Wenderott - Drexel University, Materials Science and EngineeringYong-Jie Hu (Corresponding Author) - Drexel University, Materials Science and Engineering
- Publication Details
- Chemistry of Materials, Forthcoming
- Publisher
- ACS Publications
- Number of pages
- 15
- Grants
- Grant note
- Drexel University: NA Division of Materials Research: 2334275
The authors acknowledge support from the National Science Foundation (NSF) under grants DMR-2334275 and DMR - 2529137, and from Drexel University (Carleone Faculty Award) for this research. The DFT calculations were performed partially using the Bridges2 cluster at the Pittsburgh Supercomputing Center (PSC) through allocation MAT220033 from the Advanced Cyberinfrastructure Coordination Ecosystem: Services & Support (ACCESS) program, which is supported by National Science Foundation grants #2138259, #2138286, #2138307, #2137603, and #2138296, and partially using the Picotte cluster at the Drexel University Research Computing Facility (URCF). XRD was performed in the Materials Characterization Core (MCC) at Drexel University.
- Resource Type
- Journal article
- Language
- English
- Academic Unit
- Materials Science and Engineering
- Web of Science ID
- WOS:001806656700001
- Other Identifier
- 991022193393704721