A recent study published in Advanced Materials Technologies explored a novel method to enhance the β-phase content in polyvinylidene fluoride (PVDF) composites using in situ growth of silver(I) fluoride (AgF) and silver oxide (Ag2O) nanoparticles. By increasing β-phase content, the researchers aimed to improve the electrical performance of composite films, making them more effective for piezoelectric nanogenerators in energy-harvesting applications.
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Background
PVDF is a thermoplastic polymer known for its piezoelectric properties, making it widely used in sensors and actuators. However, pure PVDF predominantly exists in the non-polar α-phase, which limits its piezoelectric efficiency. Enhancing β-phase content is crucial for improving performance, but previous methods relying on external metal nanoparticle doping have had limited success.
This study takes a different approach by incorporating silver nanoparticles directly into the PVDF matrix during film formation. The researchers investigated how in situ loading of AgF and Ag2O nanoparticles, using silver nitrate (AgNO3) as a precursor, affects the phase structure, dielectric properties, and piezoelectric response of PVDF composites. The goal was to achieve a uniform nanoparticle distribution that promotes β-phase formation and enhances overall film performance.
Experimental Approach
PVDF composite films were prepared by dissolving PVDF powder (molecular weight approximately 534,000) in anhydrous dimethylformamide (DMF) at a concentration of 120 mg/mL. Silver nitrate was added in varying weight ratios (0% to 5.6%) to determine the optimal nanoparticle concentration for β-phase enhancement. The solution was stirred at 50 °C for 12 hours, followed by a 15-minute ultrasonic treatment to ensure even dispersion of the silver precursor.
The mixture underwent degassing before being cast into films approximately 30 µm thick. The films were dried under vacuum at optimized temperatures and poled using a direct current electric field to align the dipoles. Characterization techniques, including piezoelectric force microscopy (PFM) and dielectric analysis, were used to assess the morphological, structural, and electrical properties of the films.
Results and Discussion
The study found a significant increase in β-phase content, reaching 91.4% at an optimized 1.5 wt% 1.5 wt% AgNO3 loading. This improvement was attributed to the uniform distribution of in situ grown silver nanoparticles, which facilitated the phase transition. Dielectric analysis showed a threefold increase in the dielectric constant, reaching 30.1 at 1000 Hz compared to pristine PVDF, indicating enhanced ionic mobility and polarization.
Piezoelectric performance also improved substantially. The optimized PVDF composite exhibited a 50 % increase in the piezoelectric coefficient (d33), achieving approximately 12 pC/N compared to 8 pC/N in pure PVDF. These enhancements highlight the effectiveness of in situ silver nanoparticle growth in improving the piezoelectric properties of PVDF composites.
A prototype nanogenerator built using the optimized composite film demonstrated strong performance. It generated an open-circuit voltage of approximately 35 V, a short-circuit current of 1.6 µA, and an output power density of 25 25 µW cm-² under a compressive stress of 0.5 MPa. The device successfully powered ten commercial blue LEDs and charged a 50 nF capacitor within 10 seconds, showcasing its potential for real-world energy-harvesting applications.
Conclusion
This research presents an effective strategy for enhancing the piezoelectric properties of PVDF composites through in situ silver nanoparticle growth. The method significantly increases β-phase content while improving dielectric and piezoelectric properties critical for energy harvesting applications. The strong performance of the prototype nanogenerators suggests this approach could contribute to the development of scalable and efficient energy-harvesting devices.
By combining advanced material science and engineering techniques, this study provides valuable insights into the future of flexible electronics and renewable energy technologies. Continued research in this area could further improve the efficiency and practical applications of piezoelectric materials in next-generation energy systems.
Journal Reference
Liu R., et al. (2025). Modulating D33 coefficients through in situ AgF and Ag2O growth in PVDF composites for high-performance piezoelectric nanogenerators. Advanced Materials Technologies. DOI: 10.1002/admt.202500012, https://advanced.onlinelibrary.wiley.com/doi/10.1002/admt.202500012