Glassy, ceramic, and crystalline aluminosilicates

Abstract

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 vibrational motions of Li ions in stuffed aluminosilicates were studied. Samples investigated include the polycrystal β-eucryptite, the ceramics Zerodur M and Zerodur as well as the precursor glass of the latter compound. Conductivities similar in magnitude are found for all samples at high temperatures. For temperatures well below ambient, local dielectric relaxations are observed. Their appearances strongly depend on the degree of the crystallinity of the host matrix. For the Zerodur samples, the far infrared measurements yield evidence for excess absorptions at vibrational frequencies. In order to test whether these excitations are associated with an enhanced density of states, the specific heat of several aluminosilicates has been measured for temperatures between 5 and 50 K using the adiabatic Nernts