HIGH-TEMPERATURE IMMITTANCE RESPONSE IN ANATASE-BASED SENSOR MATERIALS

The ac small-signal electrical response of anatase-based sensors is ex amined at elevated temperatures (400 degrees C less than or equal to T less than or equal to 900 degrees C) via lumped parameter/complex pla ne analysis (LP/CPA). The ac data, monitored in the frequency range 5 Hz less than or equal to f less than or equal to 13 MHz, are used to e stablish the role of microstructures on the resulting electrical behav ior in these polycrystalline materials. Two semicircular relaxations, observed in the impedance plane, are attributed to the low-frequency r elated grain boundary and high-frequency related grain response. The g rain-boundary response is difficult to quantify at elevated temperatur es via LP/CPA and dc measurements. The electrical path homogeneity is examined via the presence of the depression angle which remained nearl y invariant in the range of measurement temperatures. These features a re discussed and compared with the results obtained at room temperatur e.