K.S. Dubey

Contribution to the lattice thermal conductivity due to the correction term in the frame of the generalized callaway integral: Application to Ge

Abstract The contribution to the lattice thermal conductivity due to the correction term (due to the three phonon normal processes) has been studied at very low temperatures in the frame of the generalized Callaway integral by deriving analytical expressions for it. The contribution of the correction term towards total phonon conductivity of Ge has been calculated in the temperature range 1–5 K and negligible contribution is found due to it.

Peripheral phonons and phonon conductivity of the doped semiconductor

Abstract The percentage contribution of the peripheral phonons towards the total phonon conductivity of P-doped Ge has been studied with the help of the Ziman expression of the electron-phonon scattering relaxation rate and the Callaway integral of the lattice thermal conductivity. It is found that the percentage contribution of the peripheral phonons increases with the increase of temperature. The entire study is limited to the temperature range 1–5 K.

Lattice thermal conductivity of polyvinyl acetate at low temperatures

Abstract The lattice thermal conductivity of a non-crystalline polymer has been studied at low temperatures in the frame of the density fluctuation model by calculating the total lattice thermal conductivity of polyvinyl acetate in the temperature range 0.1–4K as an example and a very good agreement has been reported between the calculated and the experimental values of the lattice thermal conductivity in the entire temperature range of study. It is also found that at low temperatures, the lattice thermal resistivity of a non-crystalline polymer is mainly due to scattering of phonons by empty spaces.

Correction to phonon conductivity due to three phonon normal processes in the presence of dislocations

Abstract The contribution of the correction term due to the three phonon normal processes towards the total phonon conductivity has been studied in the presence of dislocations. An analytical expression including dislocations has been obtained for it. The expression obtained is used to calculate the contribution of the correction term due to the three phonon normal processes for NaF in the temperature range 1–5 K as an example.

Peripheral phonons and phonon conductivity of a metal at low temperatures

Abstract The role of the peripheral and non-peripheral phonons in the estimation of the lattice thermal conductivity of a metal has been studied at low temperatures by calculating their separate contributions towards the total lattice thermal conductivity. The study is made in the temperature range 0.4–2.5 K with the help of the Ziman expression for the scattering of phonons by the charge carriers and the Callaway expression of the phonon conductivity, and Sb is taken as an example. The separate percentage contributions due to peripheral and non-peripheral phonons have also been studied and it is found that the percentage contribution due to peripheral phonons increases with increasing temperature while the percentage contribution due to non-peripheral phonons decreases with increasing temperature. The percentage contributions of the lattice thermal resistivities due to electrons and holes towards the total lattice thermal resistivity of Sb have also been reported in the present note.

Boundary scattering and lattice thermal conductivity of semicrystalline polymer at low temperatures: Application to polyethylene

The role of the boundary scattering in the estimation of the lattice thermal conductivity of the semicrystalline polymer has been studied by calculating the total lattice thermal conductivity of polyethylene considering its non-crystalline as well as crystalline nature for the different values of the boundary scattering relaxation rate in the temperature range 0.1–5 K for the first time. The percentage contribution due to the crystalline nature towards the total lattice thermal conductivity of polyethylene has also been reported for the different values of the boundary scattering relaxation rate. It is found that below 1 K the total lattice thermal conductivity of polyethylene sample is almost independent of the boundary scattering.

Correction to lattice thermal conductivity due to three phonon normal processes in the presence of dislocations in the frame of the generalized callaway integral

The contribution of the correction term due to the three phonon normal processes to the total lattice thermal conductivity of an insulator having dislocations, has been studied in the frame of the Generalized Callaway integral by obtaining for it an analytical expression, for the first time. To test the applicability of the expression obtained, the contribution of the correction term to the total lattice thermal conductivity has been calculated for the sample of NaF having dislocations in the entire temperature range 1–5°K.

Phonon conductivity correction term: Application to P-doped Ge

The role of the characteristic temperature θ∗ (which differentiates peripheral phonons from non-peripheral phonons) in the study of the phonon conductivity correction term due to three phonon normal processes, has been studied for the first time. The study is made for P-doped Ge in the temperature range 1–5 °K for the different values of θ∗ in the range 8–24 °K as an example.

Characteristic temperature θ∗ and lattice thermal conductivity of a doped sample: Application to P-doped Ge

Abstract Role of the characteristic temperature θ∗ which differentiates non-peripheral phonons from peripheral phonons, in the estimation of the total lattice thermal conductivity of the doped sample has been studied by calculating the total phonon conductivity of P-doped Ge in the temperature range 1–5 K for the different values of θ∗, for the first time.

Lattice thermal resistivity due to the core dislocations

Abstract The lattice thermal resistivity of an insulator having core dislocations has been studied by obtaining an analytical expression for it. The lattice thermal conductivity of a sample has also been calculated for different values of the core dislocation scattering strength to see the effect of core dislocation on it.