Investigating the Effects of Sintering Variables on Microstructure and Density of PZT Fibers Fabricated via Extrusion Process

In this research, PZT fibers were fabricated using PZT-5A commercial powder, polymeric additives and deionized water as solvent. The rheological behavior of different pastes with various amounts of solids and additives was investigated and the best paste was selected for syringe injection (extrusion process). Meanwhile, the paste containing 85wt% solid content and 1wt% glycerol, which was prepared using a 15wt% PVA solution, showed the best rheological behavior. The obtained fibers were dried at 100°C and the burnout process was carried out at 600°C with heating rate of 1°C/min for 2 hours. The sintering process was carried out in the temperature range of 1220-1270 ͦC for 2.5-4 hours. The phase investigations conducted by X-ray diffraction analysis showed that the fibers sintered at 1220°C have a single-phase perovskite structure and peak splitting confirms the ferroelectric nature of fiber. However, at higher sintering temperature, secondary peaks related to zirconium and titanium oxides were observed in the fiber diffraction patterns. Scanning electron microscope (SEM) images from the surface of the fibers showed that the fibers sintered at 1220°C for 2 hours were free of any cracks and had an acceptable density. In addition, based on the SEM images from the fracture surface of the fibers, the microstructure of this sample consisted of cuboid grains with average size of 1.5 μm, which is half of the average grain size of bulk PZT with spherical grains at its optimum sintering temperature.