Low temperature, glass-like properties of crystalline beta-alumina

The low temperature properties measured for single crystal Na, Ag, K, and Li B-alumina are characteristic of those found in amorphous materials. The specific heat is dominated below 1 K by a term approximately linear in temperature instead of the cubic dependence normal for crystals. All except K B-alumina have an approximately quadratically temperature dependent thermal conductivity below 1 K and a nearly temperature independent thermal conductivity near 10 K. Both features are associated with glassy materials, while pure cryst~lline dielectrics have thermal conductivities cubic in temperature. The dielectric susceptibilities of the B-aluminas vary a few parts in 102 over three orders of magnitude in temperature, with the dependences again of the same form as those found in glasses. Unlike glasses, however, the variations of susceptibility for all but Li J3-alumina are found to be extremely anisotropic. The magnitudes of the measured properties are dependent on the species of metal ion present. Beta-alumina is a layered crystal composed of slabs of alumina separated by non-stoichiometrically occupied planes containing the monovalent cations in a disordered environment. The glass-like properties measured indicate that there is present in the Beta-aluminas a broad band of low energy excitations associated with the cations in the planes. The tunneling-states model, which explains glassy properties with excitations arising from quantum mechanical tunneling of units in double-well potentials, was used to analyze the data. An energy dependent density of tunneling states with a spectrum of relaxation times for each tunneling-state energy was found to be necessary to explain the properties of glasses and the B-aluminas.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Physics

Year dc:date

2011

Author dc:creator

• Anthony, Philip John

Contributors dc:contributor

• Anderson, A.C.

• glass-like properties
• crystalline beta-alumina
• low temperature properties
• single crystals
• amorphous materials

Statement dc:rights

• Copyright 1978 Philip John Anthony

Language dc:language

en

Identifier

356017

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/25584