Thermo-dielectric, humidito-dielectric, and humidity sensing properties of barium monoferrite and barium hexaferrite nanoparticles

[Display omitted] •Synthesis of barium monoferrite (BaFe2O4) and M−type barium hexaferrite (BaFe12O19) nanoparticles by sol–gel auto-combustion.•The formation of orthorhombic crystal structures of BaFe2O4 and hexagonal crystal structures of BaFe12O19 was investigated.•The Significant variation in the dielectric properties with both the temperature and relative humidity.•Barium ferrite humidity sensors were successfully fabricated. The resistance of the sensor goes down as the relative humidity goes up.•The M−type barium hexaferrite (BaFe12O19) humidity sensor is 1.82 times more sensitive than the barium monoferrite (BaFe2O4) sensor. Barium monoferrite and M−type hexaferrite with generic formulae BaFe2O4 and BaFe12O19 were synthesized using the sol–gel method by annealing at 1000 °C. To confirm the phase and compositions, XRD and FTIR analyses were employed, and the formation of orthorhombic crystal structure of BaFe2O4 and hexagonal crystal structure of BaFe12O19 were observed. The surface morphology of the samples was investigated through the use of the scanning electron micrograph (SEM) technique. Energy dispersive X-ray spectroscopy (EDS) confirmed the chemical compositions of the samples. At room temperature, the real part of the dielectric constant (ɛʹ), the imaginary part of the dielectric constant (ɛʹʹ), the dielectric loss tangent (tanδ), and AC conductivity (σAC) were measured at the specific frequencies (1, 1.5, and 2 MHz), and they were increased with both temperature and relative humidity (RH). Barium ferrite humidity sensors were created. The resistance of the sensor goes down as the RH% goes up, and the BaFe12O19 humidity sensor is 1.82 times more sensitive than the BaFe2O4 sensor.