The effect of Cr₂O₃ doping on structures and dielectric constants of SiO₂-Bi₂O₃-B₂O₃-Na₂CO₃ glass based on silica gel of natural sand

One of the abundant natural resources along the coastal lines of Indonesia is silica sand. One of the beaches which has a lot of silica content is Bancar-Tuban beach. Silica can be used as a raw material of glass that has multiple properties in optic, dielectric, and other physical properties by introducing specific dopants. Some oxides have been used as dopant e.g. Al₂O₃, Fe₃O₄, and NiO. However, there has not been any comprehensive study discussing the multiple properties of natural silica-sand-based glass with Cr₂O₃ dopant so far. A series of samples have been prepared, which mean two solid steps to state melting technique. Cr₂O₃ was selected as a dopant due to its potential to control its color and to increase the dielectric constant of the glass. The synthesis of silica (SiO₂) sand from BancarTuban beach was conducted through the sol-gel process. The composition varied as the addition of Cr₂O₃on 50SiO₂-25B₂O₃-(6.5-x) Bi₂O₃-18.5Na₂CO₃-xCr₂O₃ (x = 0, 0.02, 0.04, 0.06 and 0.08mol), later called SBBN glass. The samples' characterizations of the structure and morphology were conducted through the use of XRD, and SEM-EDX. The measurements were done by using a DC capacitance meter in order to investigate the dielectric properties of the sample, under the influence of light. It is shown that addition of Cr₂O₃ did not alter the crystal structure but changed the structure of the functional bond formation. It is also revealed that the dielectric constant increased along with the increasing of Cr₂O₃. An interesting result was that the dielectric constant of the glass was quantized decreasingly as the increase of light.