Giant piezoresistivity of polymer-derived ceramics at high temperatures

The piezoresistivity of a silicon oxycarbonitride polymer-derived ceramic (PDC) material is investigated at high temperatures. The resistance was measured as a function of uniaxial loading under constant current conditions. The piezoresistive gage factor was found to be in the range of 600–1700 at an applied stress of 1MPa. The gage factor depends on both the stress and temperature. The piezoresistivity was measured up to 1000 ◦C, demonstrating the viability of PDCs as piezoresistive materials at high temperatures. The Arrhenius dependence of the gage factor, ψ, gives the following expression for its temperature dependence at 1MPa: ψ = 44 exp(28,000/8.31T), where T is in Kelvin. The extrapolated values of the gage factor yield a value of 322 at 1400 ◦C, and 287 at 1500 ◦C (at an applied stress of 1MPa). A combination of stability at high temperatures, chemical durability, and large gage factor are entirely unique to PDCs making them ideal candidates for sensor materials in extreme environments.