A new method for fabrication of stable and reproducible yttria-based thermistors

Abstract

Yttria has been considered as a potential candidate for a high-temperature thermistor. Two of the main challenges with regard to commercialization of high-temperature thermistors are (i) aging of these thermistors at high temperatures and (ii) lack of suitable lead wire attachment techniques. Densification of thermistors near theoretical density seems to eliminate the aging problem. A new technique has been developed that improves the attachment of lead wire with the sensor material (yttria) leading to a significantly reduced time of manufacturing of thermistors. This technique is compared with two other techniques, namely the conventional method and in-situ lead wire attachment method (ISAM), used earlier for fabrication of high temperature thermistors. The new technique also helps achieve good density leading to the elimination of the aging problem. Aging tests had been conducted at 1000°C in different environments (O 2, N 2, air) to see the effect of environment on aging behavior. Experimental results show no evidence of aging of the thermistors manufactured by the new method. Thermistors developed via this new technique also show good reproducibility. Analysis of the thermistor/Pt lead wire interface shows no evidence of any new phase or compound formation at the interface. The SEM micrograph of the interface shows good contact between Pt lead wire and yttria.