4^th European Chemistry Congress

Biography

Biography: Chandkiram Gautam

Abstract

Glass ceramics are polycrystalline materials produced by the controlled crystallization of glass and are composed of randomly oriented crystals with some residual glass with no voids or porosity. They are truly engineered materials; capable of a wide range of microstructure and properties. They combine the ease of fabrication of a glass with the generic properties e.g. high strength; stiffness etc. of a ceramic. Ferroelectric (PbSr)TiO₃/(BaSr)TiO₃ perovskite solid solution phase has been crystallized in borosilicate glass matrix with suitable heat treatment schedule. La₂O₃/Fe₂O₃ is a donar dopant for lead strontium titanate and can make it semi conducting. Dispersion of semi conducting perovskite phase in insulating glassy matrix in glass ceramic samples may lead to the formation of space charge polarization around crystal glass interface, leading to high value of effective dielectric constant. Therefore, with the aim of developing glass ceramics with high dielectric constant, glasses in the systems [(Pb_xSr_1-x)O.TiO₂]-[2SiO₂.B₂O₃]-[K₂O]-[BaO] (1£ x£0.5) and [(Ba_xSr_1-x)O.TiO₂]-[2SiO₂.B₂O₃]-[K₂O]-[BaO] with La₂O₃ and Fe₂O addition have been prepared by melt and quenched method. XRD patterns show that perovskite PbTiO₃/BaTiO₃ is the major crystalline phase in these glass ceramics. The structure of major crystalline phase is tetragonal similar to PbTiO₃. The dielectric behavior of the glass ceramic samples prepared by heat treatment of their parent glasses. All the glass ceramic samples show a broad Curie peak in their e_r vs. T plots. The D Vs T plots also show a relaxation peak with shift to high temperature with increasing frequency. The dielectric behavior of these glass ceramic samples is attributed to space charge polarization associated with ferroelectric to paraelectric transition similar to relaxor like materials. These may be used for ceramic capacitor applications.