THE SPECIFIC HEATS BELOW 30K OF LITHIUM METAL OF VARIOUS ISOTOPIC COMPOSITIONS AND OF SODIUM METAL

Journal Article · Tue Nov 26 04:00:00 EST 1963 · Proc. Roy. Soc. (London), Ser. A

DOI:https://doi.org/10.1098/rspa.1963.0202· OSTI ID:4118070

Filby, J D; Martin, D L

The specific heats of lithium metal of three different isotopic compositions (main components 99.99 at.% Li/sup 7/, 92.7 at.% Li/sup 7/ ( approximates natural) and 99.3 at.% Li/sup 6/, respectively) and of sodium metal have been measured in the temperature range 3 to 30 deg K. The 99.99% Li/sup 7/ sample was also measured in the temperature range 0.4 to 1.5 deg K. Within experimental error the differences in the lattice specific heats of the lithium samples are in accord with theoretical expectation. The values of the Debye temperatures in the low-temperature limit are 337.0 plus or minus 2.5 deg K for 99.99% Li/sup 7/, 344.0 plus or minus 2.5 deg K for 92.7% Li/sup 7/, and 367.5 plus or minus 2.5 deg K for 99.3% Li/sup 6/. However, the temperature variation of the lattice specific heats of all the lithium samples is anomalous, because the usual minimum in the Debye temperature as a function of temperature is not observed. Both lithium and sodium undergo a marensitic transformation on cooling to the temperature range of the experiments. It was found that the amount of lithium transformed to the low-temperature phase is not increased appreciably by cooling below 20 deg K, whereas the amount of sodium transformed is significantly increased on cooling below this temperature. After rapid cooling of the sodium sample to 3 deg K, spontaneous heating is observed in the temperature range 4 to 16 deg K, the total heat emitted being about 0.05 cal/g atom. This is believed to correspond to annealing out of some of the defects introduced by the marensitic transformation. By thermally cycling the sodium sample up to 90 deg K and back to 3 deg K, the martensitic transformation was partially inhibited and the specific heats below 30 deg K of the separated b.c.c. and h.c.p. phases were deduced, the low temperature limiting Debye temperatures being about 152.5 and 159 deg K, respectively. (auth)

• Research Organization: National Research Council, Ottawa
• Sponsoring Organization: USDOE
• NSA Number: NSA-18-006118
• OSTI ID: 4118070
• Journal Information: Proc. Roy. Soc. (London), Ser. A, Journal Name: Proc. Roy. Soc. (London), Ser. A Vol. Vol: 276
• Country of Publication: Country unknown/Code not available
• Language: English

Related Subjects

ANNEALING
ATOMS
COOLING
DEBYE TEMPERATURE
DEFECTS
ENRICHMENT
ERRORS
HEATING
LATTICES
LITHIUM 6
LITHIUM 7
LITHIUM ISOTOPES
LOW TEMPERATURE
MARTENSITE
MEASURED VALUES
METALS
OSCILLATIONS
PHYSICS
SODIUM
SPECIFIC HEAT
TEMPERATURE
THERMODYNAMICS
TRANSIENTS
VARIATIONS