Nernst equation - Lambda Sensor

[H3ll4s]

Hello everyone,

I am not sure if this question is comfortable in the chemistry section but I will try my luck. I have been dealing with lambda sensors a little bit and when I look at the characteristic voltage lambda curve I keep asking myself why it flatens out when getting into the rich (lambda<1) region. I have read somewhere that it is due to the maximum electrolyte's conductivity, which makes sense but is not very satisfying. My question is whether or not this statement is correct and by which equation it can be described. I see so many plotted curves but nowhere any clues how they did it . Just a mention of the nernst equation, which only describes the part lambda>=1 (right?). And if someone also knows why the flatened part (lambda<1) decreases with increasing temperature (increase in temperature should mean increase in conductivity, thus higher voltage to my understanding) I would be very thankful.

Thanks in advance
John

 

[Bystander]

(snip) ... why it flatens out when getting into the rich (lambda<1) region. I have read somewhere that it is due to the maximum electrolyte's conductivity, which makes sense but is not very satisfying. My question is whether or not this statement is correct and by which equation it can be described.

An equation to describe oxygen transport through an uncharacterized solid electrolyte? Should be good for a Master's for you.

I see so many plotted curves but nowhere any clues how they did it . Just a mention of the nernst equation, which only describes the part lambda>=1 (right?).

The plots are of real measurements, "this vs. that."

And if someone also knows why the flatened part (lambda<1) decreases with increasing temperature (increase in temperature should mean increase in conductivity, thus higher voltage to my understanding) I would be very thankful.

Conductivity increases with T for some materials, and decreases for others. Oxygen transport should be increasing, and hydrogen transport should be increasing in the opposite direction, perhaps more quickly than the oxygen transport.