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Tuning Oxide Properties by Oxygen Vacancy Control During Growth and Annealing
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Reductive-defect-suppressed titanium oxynitrides via Ca3N2-assisted topochemical nitridation
Yuki Sasahara1, Kento Yoshii1, Daichi Kato1
1Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering, Kyoto University Kyoto 615-8510 Japan kage@scl.kyoto-u.ac.jp.
Chemical Science
|April 9, 2026
Summary
A new ammonia-free method synthesizes transition-metal oxynitrides using calcium nitride (Ca3N2). This approach offers controlled composition and enhanced visible-light photoactivity for photocatalysis and dielectric applications.
Area of Science:
- Materials Science
- Solid-State Chemistry
- Photocatalysis
Background:
- Transition-metal oxynitrides possess desirable properties for photocatalysis and dielectrics.
- Conventional synthesis methods like ammonolysis involve harsh reducing conditions, leading to defects and limited control.
Purpose of the Study:
- To develop a novel, ammonia-free synthesis route for transition-metal oxynitrides.
- To achieve controlled composition and suppress reductive defects.
Main Methods:
- One-step, topochemical nitridation using calcium nitride (Ca3N2) as a solid nitrogen source.
- Reaction of BaTiO3 with Ca3N2 at 550 °C via anion exchange (3O2-/2N3-).
Main Results:
- Successfully synthesized BaTiO3-3x/2Nx oxynitride without detectable Ti3+-related defects.
- The resulting oxynitrides exhibited tunable bandgaps, high crystallinity, and visible-light photoactivity.
- Calcium oxide byproduct was easily removed by washing.
Conclusions:
- Calcium nitride is a safe and effective reagent for controlled, ammonia-free oxynitride synthesis.
- This method enables the production of high-quality oxynitrides for advanced applications.
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