A hidden correlation between triboelectric performance and glass transition temperature in 0.80Na_0.5Bi_0.5TiO₃-0.20BaTiO₃/PDMS-based nanogenerators

Polydimethylsiloxane (PDMS)-based triboelectric nanogenerators (TENGs) embedded with 14 vol.% 0.80Na_0.5Bi_0.5TiO₃-0.20BaTiO₃ (NBT-20BT) particles of different sizes were prepared, and their morphology, temperature and frequency dielectric properties, as well as triboelectric output performance, were studied. A series of powders prepared with progressively longer milling durations showed that the particles became finer and their size distribution became narrower, as indicated by the Weibull distribution statistical analysis. The NBT-20BT/PDMS composite films exhibit a low-temperature dynamic glass transition anomaly dependent on NBT-20BT particle size. Due to strong interaction between PDMS and NBT-20BT, the glass transition temperature shifts to higher values than in pure PDMS. The triboelectric output performance of the NBT-20BT/PDMS-based TENGs, tested against an Al foil in a vertical contact-separation mode under a pressing force of 10 N, exhibited a non-monotonic behavior. For the most efficient sample, the triboelectric parameters reached 6.06 μ A, 9.78 nC/cm², and 6.23 μW/cm² for the short-circuit current, charge density, and output power density, respectively. The observed maximum in the triboelectric properties across the series is explained by the agglomeration of the corresponding powder within the PDMS, as revealed by scanning electron microscopy. An important correlation for the NBT-20BT/PDMS composite films was observed: the TENG output performance depends on the glass transition temperature in a near-linear manner.