HIGH TEMPERATURE THERMODYNAMIC PROPERTIES OF SOME OF THE RARE EARTHS

Journal Article · Thu Feb 01 04:00:00 EST 1962 · Dissertation Abstr.

OSTI ID:4813113

Berg, J R

The design and construction of a high temperature vacuum ice calorimeter is described. It was calibrated from 1100 to 1700 deg C with alpha -Al/sub 2/O/ sub 3/, and the results were compared to other studies made on this material in the temperature range indicated. This instrument was used to determine the heat content of yttrium metal from 1100 to 1675 deg C. The heat contents of lanthanum, praseodymium, europium, ytterbium, and yttrium were studied on 0 to 110O deg C using a conventional Bunsen ice calorimeter. The enthalpy of each metal was expressed as a function of temperature by fitting the data to empirical equations by a least-squares treatment; the form of these empirical equations varied for the temperature regions studied. Thus, for the range from room temperature to the high temperature crystalline transformation, a cubic expression would usually fit the data well; in the high temperature crystalline region and in the liquid, a linear expression could be used. From the empirical equations expressing the enthalpy data, the other thermodynamic functions were derived and evaluated at 50 deg intervals as well as at the transformation temperatures. The heats of crystalline transformation for lanthanum, praseodymium, europium, ytterbium, and yttrium were calculated to be 753, 760, 418, and 1189 calories per mole. The heats of fusion were calculated for lanthanum, praseodymium, europium, ytterbium, and yttrium to be 1482, 1652, 2204, 1830, and 2732 calories per mole, respectively. Quenching of the fcc modification of lanthanum in the room temperature hcp form was reduced by an annealing procedure that provided reproducible results. However, the exact amount of the higher energy form of lanthanum quenched in these studies is not known. Anomalies were found in the heat content curves of europium and ytterbium at 503 and 553 deg K. These small breaks were attributed to contributions to the heat capacity arising from 4f electronic transitions resulting from the presence of some trivalent ions in a predominantly divalent metal. The observed data confirmed density and other measurements that these two metals are primarily in the divalent state.

• Research Organization: Iowa State Univ. of Science and Tech., Ames
• NSA Number: NSA-16-022608
• OSTI ID: 4813113
• Journal Information: Dissertation Abstr., Journal Name: Dissertation Abstr. Vol. Vol: 22
• Country of Publication: Country unknown/Code not available
• Language: English

Related Subjects

ALUMINUM OXIDES
ANNEALING
CALORIMETERS
CHLORINE
CRYSTALS
DENSITY
DIAGRAMS
ELECTRONS
ENERGY
ENERGY LEVELS
ENTHALPY
EUROPIUM
FUSION HEAT
HEAT TREATMENTS
HIGH TEMPERATURE
ICE
IONS
LANTHANUM
LATTICES
LIQUID METALS
LOW TEMPERATURE
MATHEMATICS
MEASURED VALUES
METALS, CERAMICS, AND OTHER MATERIALS
PLANNING
PRASEODYMIUM
QUANTITATIVE ANALYSIS
QUENCHING
RARE EARTHS
SPECIFIC HEAT
STANDARDS
TEMPERATURE
THERMODYNAMICS
TRANSFORMATION HEAT
VACUUM
VALENCE
YTTERBIUM
YTTRIUM