Spectroscopic, mechanical and magnetic characterization of some bismuth borate glasses containing gadolinium ions

The ultrasonic parameters, the optical parameters along with the IR spectroscopy and magnetic susceptibility studies have been employed to explore the role of Gd₂O₃ in the structure of the glasses xGd ₂O₃-60B₂O₃-10MoO₃-(30-x) Bi₂O₃, with 0 ≤ x ≤ 7 mol %. IR analysis indicates that Gd₂O₃ is preferentially incorporated into the borate network-forming BO₄ units. It is assumed that Bi₂O ₃ and MoO₃ enter the structure as modifiers in the form of BiO₆ and MoO₆ only. The compositional dependence of the mechanical and the optical parameters are interpreted in terms of the transformation of the structural units BO₃ into BO₄, the increase in the number of bridging oxygen atoms, and the substitution of high bond strength Gd-O, in the place of low bond strength Bi-O bond. The results of the magnetic susceptibility reveal the paramagnetic behavior as described by the Curie-Weiss law and indicating the presence of weak antiferromagnetic exchange interactions between Gd³⁺ ions. The magnetic entropy change of the glasses was determined according to the temperature and magnetic field dependence of magnetization.