One of my material (ceramics) shows extremely low thermal conductivity at room temperature (0.5 W/mK), I measured the TC by laser flash technique. I came to know the thermal conductivity of ceramics is due to phonons and it largely depend on MFP and phonon velocity. I am not expert in this area and also we have currently no facilities to measure the same. It will be grateful if somebody can advise me, how to measure the MFP and where the facilities is available, and also what are other tools (techniques) to explain the low TC.
You can also measure the elastic properties,e.g. bulk modulus B and shear modulus G to get average sound velocity. Low TC materials has low average sound velocity:
kmin=1/3CvVml
l is the mean phonon free path, at high temperatures it is close to the interatomic distance for complex oxides.
to help udnerstand the mechanism of low thermal conductivity, please read the attached file. The are also some other paper on my Researchgate page.
Dear prof. Zhou
thank you very much for your reply. Is it possible to measure shear modulus and bulk modulus experimentally with some mechanical testing
he elastic modulus was evaluated by the impulse excitation technique .The sample was given a mechanical impulse, and the vibration was detected by a microphone and then analyzed with the resonance frequency and damping analyzer (Resonance Frequency and Damping Analyzer, IMCE, Diepenbeek, Belgium), which is a
standard testing method for dynamic Young’s modulus, shear modulus, and Poisson’s ratio by sonic resonance.
Details are on my paper: Journal of Advanced Ceramics
2015, 4(2): 94–102
thank you, but unfortuntely the technique is not available here. Is it possible to measure these values by mechanical testing like compressive strength measurement.
Only Young's modulus can be measured in this method. But, usually low TC oxides have low Young's modulus, see Clark model.
you can try to look for articles written by Ordonez Miranda whom has several papers about phonon mean free path
Dear Dr. Pulanchiyodan:
In fact, the researcher mentioned by Dr. Cuautle is a member of the RG system, consider access the links:
https://www.researchgate.net/profile/Jose_Ordonez-Miranda
https://www.researchgate.net/publication/281644035_Energy_transport_of_surface_phonon_polaritons_propagating_along_a_chain_of_spheroidal_nanoparticles
Best regards
Marcos Nobre
Article Energy transport of surface phonon polaritons propagating al...
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