R. Bohmer et al., GLASSY, CERAMIC, AND CRYSTALLINE LITHIUM ALUMINOSILICATES - CHARGE-TRANSPORT AND LOW-TEMPERATURE SPECIFIC-HEAT STUDIES, Journal of non-crystalline solids, 172, 1994, pp. 1270-1276
Using dielectric techniques in the frequency ranges from 0.01 Hz to 1
GHz and from 60 GHz to 3 THz, the transport, relaxational and vibratio
nal motions of Li ions in stuffed aluminosilicates were studied. Sampl
es investigated include the polycrystal beta-eucryptite, the ceramics
Zerodur M and Zerodur as well as the precursor glass of the latter com
pound. Conductivities similar in magnitude are found for all samples a
t high temperatures. For temperatures well below ambient, local dielec
tric relaxations are observed. Their appearances strongly depend on th
e degree of the crystallinity of the host matrix. For the Zerodur samp
les, the far infrared measurements yield evidence for excess absorptio
ns at vibrational frequencies. In order to test whether these excitati
ons are associated with an enhanced density of states, the specific he
at of several aluminosilicates has been measured for temperatures betw
een 5 and 50 K using the adiabatic Nernst method.