Dielectric and structural investigation of alkali triborate glasses

Dielectric data are provided for M2O . 3B(2)O(3) glasses (M = Li, Na, K, Rb, Cs) over a broad frequency (5 Hz-2 MHz) and temperature ranges (400-600 K). Activation energies for ionic transport and the parameters of a KWW analysis are presented. The Kohlrausch-Williams-Watts (KWW) exponent, beta, increases with alkali cation size. The mid- and far-infrared glass spectra suggest that from Li to Cs both the B-O and M-O bonding changes. The relative intensity of the high frequency far-infrared cation motion band was found to scale linearly with beta. Also, beta depends linearly on the activation energy, E-sigma, the microscopic barrier, E-alpha, the interionic distance, d(M-M), and the decoupling index at T-g. Data available on triborate and trisilicate glasses show that a simple master correlation exists between beta and T/T-g over the 0.45 < beta < 0.75 and 0.35 < T/T-g < 0.9 ranges. (C) 1998 Elsevier Science B.V. All rights reserved.