HIGH-PRESSURE INVESTIGATIONS OF GROUP III ELEMENTS. PART I. FUSION CURVES AND POLYMORPHIC TRANSITIONS OF ALUMINUM, GALLIUM, INDIUM, AND THALLIUM AT HIGH PRESSURES. PART II. PHASE TRANSFORMATIONS IN URANIUM AT HIGH PRESSURES
The fusion curves of Al and Tl to 50 kbar, and of Ga to 70 kbar, were investigated by differential thermal analysis (DTA). Comparison is made with previous work and with the fusion curve of In. A break in slope of the melting curve of Ga near 45 deg C and 30 kbar led to the discovery of a new polymorph. This phase---Ga III---is slightly less dense than Ga II, both persisting to 75 kbar. Solid-solid phase boundaries for Ga and Tl were determined by changes in volume and resistance as well as with DTA. The Ga II to Ga III transition is rapid and characterized by a substantial heat as well as a drop in resistance. From the investigation of the metastability phenomena, it is tentatively concluded that Ga III is identical with Bridgman's Ga II' and that the metastable phase studied by Defrain at one atmosphere is closely related to Ga II, The existence of three polymorphs of Tl is definitely established, although the undercooling noted by Ponyatovskii for the bcc-hcp transition was verified. The triple point for the solid Tl phases is near 115 deg C and 39 kbar, with melting of the high-pressure polymorph expected above 650 deg C and 90 kbar. The alpha - BETA , BETA - gamma , and the direct alpha - gamma phase transformations in U were studied up to 45 kbar at cooling and heating rates of 3 to 5 deg C/sec, The overheating and undercooling intervals for the alpha - BETA and BETA - gamma transformations at high pressures are about the same as the hystereses expected at zero pressure and do not vary appreciably with increasing contamination. Progressive contamination and resultant lowering of the transformation temperatures of the U samples were evident for all containers used, but were least for Ta containers. The equilibrium alpha - BETA - gamma triple point occurs at less than 31.5 kbar and greater than 803 deg C. The gamma phase is definitely more compressible than the BETA phase, and the BETA phase is probably more compressible than alpha . There is only a small hysteresis in the alpha - gamma transformation. (auth)
- Research Organization:
- California. Univ., Los Angeles. Inst. of Geophysics
- DOE Contract Number:
- W-7405-ENG-48
- NSA Number:
- NSA-17-012671
- OSTI ID:
- 4758793
- Report Number(s):
- UCRL-7128
- Resource Relation:
- Other Information: For Univ. of California, Lawrence Radiation Lab., Livermore. Orig. Receipt Date: 31-DEC-63
- Country of Publication:
- United States
- Language:
- English
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ALLOTROPY
ALUMINUM
CONTAMINATION
COOLING
DENSITY
DIAGRAMS
DIFFERENTIAL THERMAL ANALYSIS
ELECTRIC CONDUCTIVITY
EXPANSION
GALLIUM
GRAIN BOUNDARIES
HEATING
HIGH TEMPERATURE
INDIUM
LATTICES
MELTING
PRESSURE
SOLIDS
SPECIFIC HEAT
TANTALUM
TEMPERATURE
THALLIUM
THERMODYNAMICS
URANIUM
VARIATIONS
VESSELS
VOLUME