Effect of alkaline earth metal oxides on the dielectric, structural and physico-chemical properties of lithium–zinc–lead-borates

We report changes in the properties of lithium-zinc-lead-borate glass (mol%: 5Li₂O·10ZnO·60PbO·25B₂O₃) brought by substituting alkaline earth metal oxides for part of its Li₂O content. These properties include density, optical basicity, molecular structure, conductivity, dielectric properties and chemical durability. The glasses were prepared by the melting quenching technique. The effect of substituting 2 mol% Li₂O by equivalent moles of MgO, CaO, SrO or BaO on the above mentioned properties is reported. The results showed that an increase in the density and the optical basicity is noticed for samples with substituted oxides in the order MgO, CaO, SrO or BaO. The FTIR also revealed that the BO₃ units with NBOs of the glasses increase with such substitution. The chemical durability was increased for glass with substituted MgO, while it decreased for those with substituted CaO, SrO or BaO. The conductivities of the base glass sample and that substituted with MgO are found to be mainly ionic while they are mainly electronic for those substituted with CaO, SrO or BaO. The dielectric permittivity revealed a value of 11.72 for the base un-substituted glass which increased to 394.02 at room temperature for glass substituted with BaO. The substituted samples with alkaline earth metal oxides produced glassy materials of high dielectric permittivity (ε′) that could present good candidate for energy storage in electronic devices.