Any addition to pure aluminum will reduce its thermal conductivity and electrical conductivity. The magnitude of this decrease depends on the amount of additive, but even a couple of percent additions can reduce the thermal conductivity and electrical conductivity of pure aluminum several times. The same is true for various additives to pure copper.
Dear Py De many thanks for your interesting technical question. Although we are inorganic chemists with experience in lanthanide chemistry I would not really call myself an expert in solid-state chemistry and metallurgy. However I just found a few potentially useful references which might help answering your question. Please have a look at the following articles entitled:
Effect of Cerium on Mechanical Performance and Electrical Conductivity of Aluminum Rod for Electrical Purpose
Article Effect of Cerium on Mechanical Performance and Electrical Co...
Mechanisms for Ce-induced remarkable improvement of conductivity in Al alloys
https://www.cambridge.org/core/journals/journal-of-materials-research/article/mechanisms-for-ceinduced-remarkable-improvement-of-conductivity-in-al-alloys/9DD686C179F53B383C0A1E17B2527FB4
High Performance Aluminum-Cerium Alloys for High- Temperature Applications
https://www.osti.gov/servlets/purl/1409366
The latter article can be downloaded as free pdf file.
The second study comes to the conclusion that the addition of proper amounts of cerium leads to a remarkable improvement of the electric conductivity of Al alloys. The addition of Ce enhances the formation of binary, ternary, or quaternary compounds of Ce, Si, Fe, and Al and simultaneously reduces the content of Fe and Si in the Al solution.
Hello All,
I make the following observation. Vadim Verlotski approaches the question from the assumption that the aluminun is pure, i.e., zero impurities, while Frank T. Edelmann approaches the same question from the assumption the aluminum is impure, i.e., nonzero amount of impurities. Both their answers are correct from their respective assumptions. If you add foreign atoms to pure aluminum you create scattering centers that increase the electrical resistivity (and decrease the thermal conductivity). On the other hand, if you add cerium to the impure aluminum for some reason it decreases the concentration of the scattering centers that were orginally present by forming, perhaps, intermetallic compounds or regular inorganic compounds that, perhaps, are insoluble or concentrate at grain boundaries, thus, decreasing the scattering centers also decreases the electrical resistivity (increases the thermal conductivity).
These ideas have been formalized by Matthiessen's rule (for the separation of electrical resisitivity into the sum of a part due to impurities, scattering centers, plus a part due to phonons), and the Wiedemann-Franz law (which says that under some conditions the ratio of electrical conductivity to thermal conductivity is proportional to temperature, i.e., they rise and fall together). Note, if the ambient temperature is constant, then the ratio is also constant, meaning, again, that the two conductivities rise and fall together due to the effects of impurities.
Regards,
Tom Cuff
Dear Py De many thanks for your message. Apparently something went wrong with the citation of the link to the second article. It can be found on the internet when you search for the title. Please find attached a pdf file for your information.
Good luck with you research! 👍
Dear Py De, in addition to all the interesting answers I will add the following general remark about the physical kinetics of the thermal conductivity coefficient:
Cerium (Ce) as an impurity does affect both thermal conductivities: of phonons and of electrons in some compounds at a certain range of temperatures T according to recent research *. We have two different thermal conductivities in solids and some metallic solutions since heat can be carried by electrons or by lattice vibrations (phonons).
Usually, the behavior of Ce as a dopant is as follows: as a concentration x in Cex increases both thermal conductivities seem to decrease.
Please check the reference, although is not for Aluminium (Al) (which is a normal metal), it is for a semiconductor Sn1−xSe.
One interesting fact that these authors reach * is that Cex doping decreases both lattice and electron thermal conductivity in semiconductors, and it would be interesting to know from your work what happens to Cex in Al alloys or metallic solutions.
* "Effect of doping level and compensation on thermal conductivity in CexSn1−xSe solid solutions" Low-Temperature Physics (2020) by Sh. Ismailov, J. Huseynov et al. Vol 46, 1114
Article Effect of doping level and compensation on thermal conductiv...
Hello Py De ,
I was interested to hear that with increasing amounts of cerium the mechanical properties decreased. Some added impurties have the effect of changing the grain size, which can present itself as a change in mechanical properties. For example, when they started using tungsten filaments in incandescent light bulbs, they noticed that the filaments became mechanically weaker with continued use due to an increase in grain size. To counteract this behavior, small amounts of thoria (thorium dioxide) were added to inhibit grain growth. Apparently, the thoria (thorium dioxide) was accumulating at the grain boundaries, and in this way suppressing grain growth.
It is possible that the cerium in aluminum is affecting the electrical, thermal, and mechanical parameters by several different and competing mechanisms including encouraging or suppressing grain growth.
One last thing, cerium, in particular its oxides, can also strongly influence the optical properties of certain substances. You are, no doubt, aware that the extraordinary brightness of the Welsbach mantle (Auer mantle or gas mantle) is due to the presence of exactly 1% by weight of one of the cerium oxides mixed with 99% by weight thorium dioxide. This delicate structure gets its mechanical strength from the presence of a tiny amount of beryllium oxide, which suppresses grain growth in the ashed mantle.
Regards,
Tom Cuff
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