Ultrasonic and structural studies on TiO2-doped CaO-Al2O3-B2O3 glasses

TiO2-doped 30CaO-30Al(2)O(3)-40B(2)O(3) glasses have been prepared by the melt quenching method over a wide range of composition (TiO2 = 5, 10, 15, and 20 mol\%). The longitudinal velocity and attenuation of ultrasonic waves were measured in these glasses at room temperature using the pulse-echo technique. The acoustic impedance and longitudinal modulus were calculated and are discussed quantitatively in terms of the structural parameters, such as packing density, dissociation energy per unit volume, field strength of the modifiers, number of network bonds per unit volume, average cross-link density and the number of two-well systems (loss centers) per unit volume of the glass. The composition dependence of these parameters suggested that Al2O3 associates itself with CaO to form AlO4 tetrahedra and Ti4+ ions are incorporated in the network as TiO6 octahedra. This leads to an increase in the three-dimensional linkage and rigidity of the network. Moreover, the theoretical elastic moduli were calculated for these glasses from the chemical composition and the experimentally determined density using the Makishima and Mackenzie model. Results showed that the model is valid for the studied glasses. (C) 2003 WILEY-VCH Verlag GmbH \& Co. KGaA, Weinheim.