I am calculating the phonon contribution to thermal conductivity for 4 perovskites (BaZrO3, BaSnO3, BaHfO3, and KTaO3) with relatively wide bandgap. When I compare my results for BaZrO3 to the experimental results, I see very good agreement at temperatures below 600K. However, as temperature increases from 600K to 1500K, my calculations underestimate the thermal conductivity with increasing error. This is similar with other theoretical methods that I have found.
My assumption is that I have calculated the phonon contribution correctly and simply there is another mechanism of heat transfer to account for this error. I am also assuming that even at these elevated temperatures, the contributions to heat transfer from electrons is not going to account for this much of a difference in thermal conductivity because of the larger bandgaps. This leaves the mechanism of radiative heat transfer where thermal energy is being carried by photons. I do not know much about this mechanism other than that it is really only important at these higher temperatures.
I am hoping to get some feedback on how I can explain the difference between my results for the phonon contribution to thermal conductivity and the measured experimental value for thermal conductivity of BaZrO3 and whether the mechanism of radiative heat transfer is a source of the error between the values.
I have attached a plot that includes my calculation results in red, results from a different theoretical calculation in blue, and the experimental measurements in green. For citation the data I am comparing my results to was both calculated and measured in the work presented in the following paper:
Article Theoretical and experimental investigations on high temperat...
Ion Dosa Thank you so much for your interest in my question. The bandgap for BaZrO3 is quite large (4.8-5.3 eV). Even with some reduction of the gap from the increase in temperature, will this gap become small enough for a significant increase in the heat transfer from free electrons? This I am not so sure and would like to hear your response.
Since posting the original question, I have also began to consider the effects of oxygen vacancies and how the number of vacancies would increase with elevated temperature. Do you have any comments on this as well?
Again, thank you.
Maybe You will find some answers here. Chapter Thermal Conductivity of Liquid Metals
I think that the effects of oxygen vacancies must be taken into account as well. Most likely it is the cumulative effect of several mechanisms that potentiate each other. I have not dealt with that kind of problems in my research, so I cannot say that I have studied them in depth.
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