AC conductivity, dielectric and thermal properties of three-phase hybrid composite: PVA/Bi2O3/cotton microfiber composite

Abstract

The impact of bismuth (III) oxide (Bi2O3) on the characteristics of the cellulose/polyvinyl alcohol (PVA) blend was reported for a high weight ratio of the oxide (15wt%). Composite samples were made with 15wt% oxide and 2:1 weight ratio of PVA to cellulose using a hot hydraulic press technique (5 MPa and 175 °C), which led to samples in the form of a disk. The thermal stability of the composite was illustrated using the thermal gravitational analysis (TGS) at a heating rate of 10 °C min−1 in N2 environment. The results show that the thermal stability of the composite sample was greater than that of the blended sample in the high-temperature region. The blend and composite samples exhibited two weight-loss stages throughout the thermal decomposition process. These two stages correspond to the slow decomposition (200 to 400 °C) and fast decomposition stages (400 to 450 °C for blend and from 430 to 460 °C for composite). Only 5% mass loss for both samples was detected due to heating from 50 °C to 200 °C. Dielectric spectroscopy (from 100 Hz to 1 MHz) was used to investigate the effects of Bi2O3 on the relaxation and conduction mechanisms of the composite samples at different temperatures. Dielectric permittivity, AC conductivity, electrical modulus, and complex impedance were investigated. Jonscher’s equation was applied to the blend and composite samples. The modified Jonscher’s equation fit well at low temperatures. As the temperature increases, the deviation from the normal Jonscher equation decreases. The activation energies of the blend and composite were calculated by determining the bulk resistance (RB) from the Nyquist plots. The activation energy of the blend was increased by adding the filler (Bi2O3).