الفهرس | Only 14 pages are availabe for public view |
Abstract The glasses systems 10 xBaTiO3(BT)- xPbTiO3(PT)-60V2O5-30B2O3 with x= 0, 2.5, 5, 7.5 and 10 mol% were prepared by the conventional melt-quenching technique. The raw material was grinded and melted in electric furnace at 1250° C for 90 min. the glassy nature of the sample was confirmed using X- ray diffraction (XRD) and differential scanning calorimetry (DSC). The as-prepared glass samples were heat treated in air at 350 °C for 2 h. 10 % PT sample heat treated at 304 °C for different periods of time: 1,2,4,8 and 24 h to obtain glass ceramic nano-composites. The effects of heat treating temperatures and times on the structural, electrical and dielectric properties were investigated by XRD, High resolution transmission electron microscope (HRTEM), Raman, Dc conductivity and dielectric measurements. from the XRD studies it is observed that homogenous glasses are formed for BaTiO3 concentration between 0–10 mol %. The heat treated samples show small diffraction peaks associated with the growth of the crystalline phase in the glassy matrix. DSC studies show an endothermic dip due to glass transition (Tg) and exothermic peak corresponding to crystallization (Tc). The glass transition temperature (Tg) increases with increasing BaTiO3 content showing an increase in bridging oxide (BO). HRTEM along with SAED images show a small crystalline phase (polar clusters) embedded in the glass matrix for all glass samples. These clusters grow in size after heat treatment process. The 10 % PT glass ceramic nano-composite show a growth in the crystalline phase with the increase in heat treatment time. Raman scattering was used to study the structure of these glasses and to confirm the existence of an intermediate range order (polar clusters) in the glassy matrix. |