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|Title:||The Low-Temperature Specific Heat of Palladium-Hydride and Palladium-Deuteride|
|Author(s):||Storm, Leonard Eugene|
|Department / Program:||Physics|
|Degree Granting Institution:||University of Illinois at Urbana-Champaign|
|Subject(s):||Physics, Condensed Matter|
|Abstract:||The low temperature specific heat of palladium hydride and palladium deuteride, as a function of hydrogen (deuterium) content, has been measured in the temperature range from 1.7 K to 7 K, using high purity, bulk samples of polycrystalline palladium. Loading of the sample with hydrogen or deuterium was accomplished using an electrolytic technique.
A computer-assisted, adiabatic specific heat apparatus was designed and built to perform the specific heat measurements. The computer, a Digital Equipment Corporation LSI-11 minicomputer, was used to optimize various equipment parameters prior to the measurement of a specific heat data point. The computer set the thermometer and heater currents and controlled the acquisition of data through the use of two digital voltmeters. Voltage readings and their associated times of occurrence were automatically stored in a file. The computer then processed the data to arrive at a value for the specific heat.
The automated specific heat apparatus has been used to determine the values of (gamma) and (theta)(,D) in bulk samples of PdH(,x) and PdD(,x) for 0.82 < x < 0.88. Using a magnetic field, normal state measurements have been made below T(,c). The values of (gamma) and (theta)(,D) obtained in this way were found to be larger than those obtained by extrapolation from above T(,c).
Values of (gamma) were found to increase with increasing hydrogen (deuterium) content. The density of states at the Fermi level, N(O), and the electron-phonon coupling constant, (lamda), have been derived from the measured values of (gamma) and T(,c) and also showed an increase with increasing composition. Differences in N(O) for hydrides and deuterides of nearly equal composition indicated an electronic difference between hydride and deuteride.
Finally, a low temperature anomaly found in the specific heat data has been observed which is believed to be due to tunneling states. Values of excess entropy associated with the anomaly showed a correlation with hydrogen concentration. An isotope effect was also observed in the anomaly.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1980.
|Date Available in IDEALS:||2015-05-13|