Premium
Conduction and Dielectric Loss Mechanisms in β‐Alumina and Glass: A Discussion Based on the Paired Interstitialcy Model
Author(s) -
INGRAM MALCOLM D.
Publication year - 1980
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1980.tb10713.x
Subject(s) - polarizability , conductivity , ionic conductivity , relaxation (psychology) , dielectric , alkali metal , electrical resistivity and conductivity , dielectric loss , ionic bonding , thermal conduction , ion , polarization (electrochemistry) , materials science , mineralogy , chemistry , condensed matter physics , composite material , electrode , physics , psychology , social psychology , optoelectronics , organic chemistry , quantum mechanics , molecule , electrolyte
A paired interstitialcy model is used as a basis for qualitative comparisons of conductivity and dielectric phenomena in β‐alumina crystals and in glass. Thus, the increase in the conductivity of sodium silicate glasses with increasing Na 2 O activity can be explained if the concentration of (Na 2 *) 2+ interstitial pairs increases with increased polarizability of O 2‐ ions, expressed in terms of the optical basicity parameter, Δ. Similarly, the occurrence of the pronounced minima in conductivity isotherms (the mixed‐alkali effect in glass) is attributed to disappearance of mobile interstitial pairs, e.g. (Li 2 *) 2+ or (K 2 *) 2+ , and the stabilization (by polarization interactions) of apparently immobile mixed‐alkali pairs, (LiK*) 2+ . The phenomenon of coionic conduction in certain β‐alumina crystals is an interesting departure from this general pattern. The orientation dependence of the electrical modulus spectrum of monocrys‐talline β‐alumina highlights the presence of a bimodal distribution of relaxation times, in which the low‐frequency component ( v 0 =10 11 Hz) may arise from the rearrangement of interstitial pairs and the high‐frequency component ( v 0 =2×10 12 Hz) may arise from less hindered ionic motions. It is suggested that the motions of interstitial pairs and surrounding cations are mutually catalytic and that some form of combined motion is responsible for both the electrical and mechanical relaxations in β‐alumina and glass.