Are there known examples for such a behaviour?

Victor V Solovyev I have prepared Cu3Sb1-xSnx samples. While increasing the Sn dopant concentration in the Sb site, the lattice thermal conductivity is increasing. Generally, the introduced mass and strain fluctuations in the lattice after Sn-doping should impede the phonon propagation and decrease the lattice thermal conductivity, but in my case its increases.

It is possible due to enhanced density?

But Sn is lighter than Sb so phonon propagation should be easier. Moreover, you are introducing a certain amount of electrons, might this account for extra thermal conductance? 0

On the other hand, cubic Cu3Sb and Cu3Sn have quite similar structures where the latter is only slightly larger (about 0.1 A) than the former. So effectively you are not introducing a large amount of strain or deformation.

Finally, you can check if the thermal conductivity of Cu3Sn is expected to be larger than Cu3Sb. If this is the case, I would say that you should expect this behaviour as while increasing the doping you will be increasing the thermal conductivity.

Immanuel Paulraj with your explanations it became more clear with the question.

As Roberto D'Agosta already mentioned, the first thing you should check is whether the conductivity you measured corresponds to the lattice alone. It might well be the case that the changes in the total thermal conductivity is due to free electrons.

Also one could consider a chance that your 'pure' Cu3Sb crystal has in fact a worse crystalline structure than a ternary Cu3Sb1-xSnx alloy. It should checked by XRD.

Apart from these two points, of course one should expect that both perfect Cu3Sb and perfect Cu3Sn have better thermal phonon-assisted conductivity than any of Cu3Sb1-xSnx alloys - because of the reason mentioned in the original question.

Well, Prof. Immanuel Paulraj is not so easy to guess, since dopping content can be magnetic or not magnetic. but lattices are phonons, and we usually study are dressed fermion by impurities. I have not seen the first work yet on bosons and impurities and I do not know how if the Larkin equation is valid for phonons as well, thinking lightly, of course, I will think harder.

In normal metals, if nimp increases the inverse scattering lifetime increases, so my question to you is:

What is the dependence of the inverse scattering lifetime in your case of phonon thermal conductivity, could you show the equation, please? Can you separate it experimentally from other contributions such as dislocations, electrons, holes, or other quasiparticles like "vacantions" (empty atomic lattice places)?

Best Regards, thank you in advance. This is a problem related to a disorder, a hard one.

Pedro L. Contreras E. the electronic thermal conductivity (ke) is calculated using the Wiedemann-Franz law, i.e., ke =s LT, under the assumption that the relaxation times for the electronic and thermal processes are the same. To obtain L, we need to find the reduced Fermi energy from the experimentally determined Seebeck coefficient by solving the following equations using the assumption that the charge carriers are dominantly scattered by acoustic phonons

Very interesting expression, Prof. Immanuel Paulraj I have never seen it before, thank you.

Looks like in these expressions, L here is the new Lorenz coefficient - L (η), S(η) - is the new Seebeck coefficient and where disorder enters? is in the parameter η?

ke = S(η) L(η) T ? does η have some expression or is it just an empirical dimensionless parameter?

Best Regards.

PD. I found this but is not similar: https://arxiv.org/pdf/1904.03183.pdf

I am not sure that the Wiedemann-Franz rule can be used for semicontuctors - probabyl not. It is an empirical rule for metals. In semiconductors the number of active charge carriers changes rapidly with the temperature, so it is not so obvious to separate the electronic and lattice heat conduction.

I am not sure that the Wiedemann-Franz rule can be used for semicontuctors - probabyl not. It is an empirical rule for metals. In semiconductors the number of active charge carriers changes rapidly with the temperature, so it is not so obvious to separate the electronic and lattice heat conduction.

I am not sure that the Wiedemann-Franz rule can be used for semicontuctors - probabyl not. It is an empirical rule for metals. In semiconductors the number of active charge carriers changes rapidly with the temperature, so it is not so obvious to separate the electronic and lattice heat conduction.

You can try the physics exposed in Solid State Communications 350 (2022) 114767. Doping affect carrier density, phonon frequency and phonon damping and how all these affect conductivity, lattice and electronic heat conductivity ta different temperature range. These things are exposed systematically in the above paper using experimental data of Na doped SnSe. Hope this helps.