Effect of BaTiO3 on the sensing properties of PVDF composite-based capacitive humidity sensors

Capacitive humidity sensors consisting of materials such as polymers, ceramics, and piezoelectrics are widely used to monitor relative humidity levels. The effect of barium titanate (BaTiO3) nanoparticles on the humidity sensing properties, dielectric response, thermal stability, and hydrophilicity of the polyvinylidene fluoride (PVDF)-BaTiO3 composite films is investigated. Hydrophilicity and surface morphology of the PVDF-BaTiO3 composite films are modified for the development of a good humidity sensor. The nanocomposite solutions are prepared by mixing an optimized concentration (2.5 wt%) of PVDF with different concentrations (0.5, 1, and 2 wt%) of BaTiO3 nanoparticles. X-ray diffraction, thermogravimetric analysis, field emission scanning electron microscopy, and contact angle measurements are used to characterize the structure, morphology, thermal stability, and hydrophilicity of the spin-coated sensing films. The dielectric study of PVDF-BaTiO3 composite film shows that as the concentration of BaTiO3 particles increase, the dielectric constant of the composite films increases as well. PVDF-BaTiO3 (2.5 wt%-1 wt%) based capacitive sensors show stable capacitive response and low hysteresis as compared to the other concentrations of the PVDF-BaTiO3 composites. The maximum hysteresis of the capacitive PVDF-BaTiO3 (2.5 wt%- 1 wt%) humidity sensor is found to be ~2.5%. The response and recovery times of the PVDF-BaTiO3 (2.5 wt%-1 wt%) based capacitive sensors are determined as 40 s and 25 s, respectively, which are significantly lower than those reported for the other PVDF composite based sensors.