Temperature Sensitivity of Flexible Co3O4/PVDF Dielectric Nanocomposites

Temperature-sensitive and flexible nanocomposite films are prepared by doping a poly(vinylidene fluoride) (PVDF) matrix with cobalt oxide (Co3O4) nanoparticles. The structural and morphological characterization, dielectric properties, and conductivity of the Co3O4/PVDF nanocomposites are then systematically investigated. The nanocomposite film loaded with 10 wt.% Co3O4 displays dielectric permittivity of 37 at 1 kHz, which is about 274% higher than that of pristine PVDF (13.5 at 1 kHz). The dielectric constant of the 10 wt.% Co3O4/PVDF nanocomposite as a function of absolute temperature can be fitted as T=26.62×ln(εr-40.595)/1.335×10-5\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ T = 26.62 \times \ln \left( {(\varepsilon_{r} - 40.595)/1.335 \times 10^{ - 5} } \right)$$\end{document} over a range of 300–423 K at 1 kHz. This fitting formula may provide important reference values for the design of flexible temperature sensors. The temperature coefficient of the dielectric constant (at 1 kHz) for the 10 wt.% Co3O4/PVDF nanocomposite film is 0.94% K−1 within a range of 350–423 K, and conductivity of about 5.78 × 10 −5 S/cm is achieved at 383 K, which is four orders of magnitude larger than that for the pristine PVDF (3.9 × 10−9 S/cm). These results show that the addition of Co3O4 nanoparticles in PVDF matrix significantly improves the dielectric constant and temperature sensitivity of the composites. Thus, the Co3O4/PVDF nanocomposites show potential application prospects in miniaturized and flexible temperature sensors.