Sodium bismuth titanate (Na0.5Bi0.5TiO3, NBT) is a representative lead-free piezoelectric ceramic with ferroelectric and piezoelectric properties, promising candidate for piezocatalytic applications driven by mechanical vibration. In this study, NBT-based perovskite fine powders were prepared by ultrasonic spray pyrolysis (USP), a continuous aerosol process based on droplet-level reaction control. The effect of pyrolysis temperature, varied from 700°C to 950°C, on phase formation and particle morphology was investigated. At lower temperatures, Bi-based secondary phases predominated, whereas the perovskite phase gradually developed with increasing temperature. The powder synthesized at 950°C exhibited a well-defined perovskite crystal structure with improved crystallinity. FE-SEM analysis showed that the powders consisted of spherical particles with an average size of approximately 750 nm, without severe interparticle agglomeration. EDS analysis confirmed a relatively homogeneous distribution of Na, Bi, Ti, and O, with Na-rich composition, consistent with Na-rich precursor condition. Piezoresponse force microscope (PFM) measurements verified the ferroelectric and piezoelectric responses of the powder synthesized at 950°C. In Rhodamine B degradation tests under probe-type ultrasonication, adding the NBT-based powder increased the reaction rate constant from 7.96×10-3 to 1.16×10-2 min-1. These results suggest that USP is a feasible continuous process for preparing NBT-based perovskite fine powders for lead-free piezocatalytic applications.

1. Introduction 
2. Experimental Section 
    2.1 Preparation of Precursor Solutions 
    2.2 Ultrasonic Spray Pyrolysis Process 
    2.3 Powder Characterization 
    2.4 Evaluation of Piezoelectric Catalyst Performance 
3. Results and Discussion 
    3.1 Phase Formation Behavior According to USP Pyrolysis Temperature 
    3.2 Changes in Particle Shape and Microstructure According to USP Pyrolysis Temperature 
    3.3 Composition and Surface Chemical State 
    3.4 Ferroelectric and Piezoelectric Properties and Piezoelectric Catalytic Performance 
4. Conclusion 
Funding
Conflict of Interest 
Data Availability Statement 
Author Information and Contribution 
Acknowledgments
References

• Hee Yeon Jeon(Department of Materials Science and Engineering, Seoul National University of Science and Technology, Seoul 01811, Korea)
• Jae Min Park(Department of Materials Science and Engineering, Seoul National University of Science and Technology, Seoul 01811, Korea)
• Ju Eun You(Department of Materials Science and Engineering, Seoul National University of Science and Technology, Seoul 01811, Korea)
• Young-In Lee(Department of Materials Science and Engineering, Seoul National University of Science and Technology, Seoul 01811, Korea, The Institute of Powder Technology, Seoul National University of Science and Technology, Seoul 01811, Republic of Korea) Corresponding author