Thermal wave propagation in single crystals of bismuth at 4 K

1970 ◽  
Vol 48 (10) ◽  
pp. 1200-1207 ◽  
Author(s):  
C. R. Brown ◽  
P. W. Matthews
Keyword(s):  
Thermal Conductivity ◽  
Wave Propagation ◽  
Single Crystals ◽  
Thermal Wave ◽  
Low Temperatures ◽  
Continuous Wave ◽  
Quantitative Agreement ◽  
Signal Frequency ◽  
Second Sound ◽  
Thermal Signal

We present preliminary results from continuous-wave experiments made on two single crystals of bismuth. The object of the experiments was the examination of the initial deviations from diffusive propagation with increasing thermal signal frequency. The thermal conductivity of bismuth is phonon-dominated at low temperatures and has a peak of the type found in good dielectric crystals. However, the observed initial deviations were not in quantitative agreement with results obtained by applying a simple theory of second sound in dielectric crystals.

Thermal Conductivity of Single-Crystal and Sintered RBa2Cu3O7 at low Temperatures

1987 ◽  
Vol 99 ◽  
Author(s):  
J. E. Graebner ◽  
L. F. Schneemeyer ◽  
R. J. Cava ◽  
J. V. Waszczak ◽  
E. A. Rietman
Keyword(s):  
Thermal Conductivity ◽  
Particle Size ◽  
Single Crystals ◽  
Free Path ◽  
Low Temperatures ◽  
Rayleigh Scattering ◽  
Resonant Scattering ◽  
Sintered Sample ◽  
Mean Free Path ◽  
Strong Scattering

ABSTRACTThe thermal conductivity k of micro-twinned single crystals of YBa2Cu3O7 and HoBa2Cu3O7 and a sintered sample of YBa2Cu3O7 has been measured for temperatures 0.03<T<5K. For the single crystals, k is small and varies as T1.8-1.9 This behavior resembles k for glassy insulators except for the lack of a plateau above IK. It is concluded that the thermal carriers are phonons with their mean free path limited by resonant scattering from tunneling entities, as in glasses. Suggestions for the location of tunneling systems are given. For the sinter, k is still smaller but does not follow a power law T-dependence. It is similar to other sintered ceramics with the same particle size, where the phonon mean free path is dominated by Rayleigh scattering from the particles. This strong scattering from the microstructure presumably masks the scattering from TS within each particle.

THE ATTENUATION OF SECOND SOUND IN LIQUID HELIUM II ABOVE 1°K.

1954 ◽  
Vol 32 (6) ◽  
pp. 381-392 ◽  
Author(s):  
K. R. Atkins ◽  
K. H. Hart
Keyword(s):  
Thermal Conductivity ◽  
Continuous Wave ◽  
Pulse Length ◽  
Boundary Effects ◽  
Second Sound ◽  
Sound Beam ◽  
Helium Ii ◽  
Viscosity Effects ◽  
Order Of Magnitude ◽  
Good Agreement

The second sound was in the form of a pulsed continuous wave with a pulse length of 1 to 2 msec, and a carrier frequency of 10 or 20 kc./s. The change in amplitude of the pulse was measured as the distance between the transmitter and the receiver was varied. To avoid boundary effects, no propagation tube was used and allowance had to be made for the spreading of the second sound beam. The attenuation was found to increase with increasing second sound amplitude. The attenuation extrapolated to zero amplitude had a finite value which increased rapidly as the temperature was lowered towards 1°K. Its order of magnitude was too large to be explained by viscosity effects, but was in good agreement with a thermal conductivity effect predicted by Khalatnikov.

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