EFFECT OF TiO2 ON STRUCTURE AND DIELECTRIC PROPERTIES OF RO-Al2O3-B2O3-SiO2(R = Ca, Mg) GLASSES

RO-Al2O3-B2O3-SiO2 (R = Ca, Mg) glasses containing different concentrations of TiO2 (ranging from 0 to 9 mol.%) were prepared by conventional melting method. When TiO2 was present in lower concentrations (<= 6 mol.%), Fourier-transform infrared spectroscopy (FTIR) indicated that titanium ions took part in network forming positions. However, for further increase in the concentration of TiO2 (>6 mol.%), FTIR data indicated the formation of TiO4 tetrahedrons and TiO6 octahedrons. The glass transition temperatures (T-g) were determined using a differential scanning calorimetry (DSC). The T-g variation with the concentration of TiO2 showed an increasing trend up to 6 mol.% of TiO2 and beyond this concentration, T-g was found to decrease. The dielectric constant epsilon(r) and loss tan delta continued to decrease with the concentration of TiO2 up to 6 mol.% and beyond that epsilon(r) and tan delta were found to increase. This behavior was mainly explained in terms of the rigidity of glass network.