Ferroelectric temperature sensors for thermometric titrations and enthalpimetric analysis

Abstract

The capabilities of commercially available barium titanate ferroelectric ceramics with switching points of 25 and 0°C were tested for use in thermometric titrations. Temperature ( T) versus resistance ( R) data taken from 24 to 26°C for seven ferroelectrics and from −1 to +1°C for three others were fitted to an exponential equation of the form R = Aexp( CT), where A is a scaling factor and C is the temperature coefficient of resistance. A ferroelectric sensor (FES) was wired in a Wheatstone bridge in place of the thermistor customarily used in conventional instrumentation. Calculations substantiated that the bridge imbalance potential response approximated linearity within any 1°C interval, provided that the bridge was balanced in the middle of the span. The response of the FES bridge showed a fourfold enhancement for a given temperature change compared with the thermistor bridge and a concomitant reduction in baseline noise. Analytical capabilities are illustrated by thermometric redox titrations in the concentration range between 3 × 10 −5 and 2 × 10 −3 M.