EFFECT OF HIGH PRESSURE ON THE ELECTRICAL RESISTANCE OF Bi, Yb, AND Dy (thesis)
The experimental procedure of measuring the electrical resistance of Bi, Yb, and Dy is discussed in detail. By using Bridgman anvils, pressures as high as 100 kbars and temperatures between 77 and 633 deg K were reached. Above about 150 deg C, the temperature coefficient of resistance of bismuth is positive, as for a metal. Below 150 deg K in the region l5 to 35 kbars, the coefficient becomes negative, as is characteristic of semiconductors. When the exponential resistance formula is applied to the region in which bismuth is a semiconcuctor, the energy gap is found to be 0.006 ev at 15 kbars, with a steady rise to 0.018 ev at 35 kbars. At higher pressures, bismuth I transforms into a metallic modification with the normal temperature dependence of the resistance. The phase line for the large peak in the resistance-pressure isotherms of ytterbium was determined from 77 to 633 deg K. The value of dT/dP is about -20 deg/kbar, and the phase line extrapolates close to the known 1 atmosphere alpha - BETA transition. In the region 20 to 45 kbars, ytterbium shows a negative temperature coefficient of resistance. When the exponential resistance formula for semiconductors is used, ytterbium shows an energy gap of 0.015 ev at 20 kbars, an increase to a maximum of 0.080 ev at 37 kbars, and then a decrease to 0.05 ev at 45 kbars. Dysprosium was examined at 20 deg C and in the region 77 to 200 deg K. The Neel temperature decreases with pressure; dTN/dP is --0.52 plus or minus 0.04 deg/kbar. The Neel transition disappears in the region 45 to 55 kbars. The transition affecting the Neel line is visible as a shoulder in the resistance- pressure isotherms. Above the Neel line, dT/dP for this shoulder transition is very large and the sign of the slope is unknown. Below the Neel line, dT/dP is between --1 and --4 deg/kbar. The nature of this transition is unknown. (auth)
- Research Organization:
- California. Univ., Berkeley. Lawrence Radiation Lab. and California. Univ., Berkeley. Dept. of Chemistry
- DOE Contract Number:
- W-7405-ENG-48
- NSA Number:
- NSA-18-018358
- OSTI ID:
- 4038466
- Report Number(s):
- UCRL-11220
- Country of Publication:
- United States
- Language:
- English
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