Research On The Matching Between Structure And Performance Of Limit Current Oxygen Sensor

The limiting current type oxygen sensor can continuously detect the air-fuel ratio in the lean combustion region,which is a popular research direction for automotive oxygen sensors.During the working process of the limiting current type oxygen sensor,the thermal expansion coefficient does not match between the materials of insulating layer and the functional layer.When conducting the thermal shock process,thermal stress is generated,resulting in structural damage,which has a great influence on the service life of the oxygen sensor.This article focuses on the effect of the addition of the transition layer on the performance of the simplified insulating and functional layers.The structure of the gradient transition layer and the dentate transition layer was optimized by the finite element method.The alumina precursor was prepared by the low temperature solid phase method.Through the casting,printing,laminating and co-sintering processes,a co-sintered sample of the transition structure was prepared.The strength and morphology tests were performed on these samples,and the following conclusions were analyzed:(1)Both the gradient transition layer and the dentate transition layer can improve the thermal stress distribution of the structure.The gradient transition layer reduces the stress on the bonding surface.The dentate transition layer concentrates stress on the fixed surface.Selecting a dentate transition layer with a tooth width of 0.5 mm can reduce the stress concentration and improve the stress distribution at the bonding surface.(2)The citric acid complex of hydrated basic aluminum acetate has a sintering temperature of 375°C.The co-sintered sample of the transition layer needs to be kept at this temperature in the sintering process so as to completely decompose the precursor.(3)Both the gradient transition layer and the dentate transition layer can reduce the structural thermal stress.Compared to the cross-teeth transition layer,gradient transition layer can strengthen the structure and ensure the performance of insulation layer.