The most widely used piezoelectric ceramic composition is “lead zirconate titanate (PZT)”. Of this composition, PZT8 and PZT4; Used in ultrasonic transducers such as welding, cutting, sonar. These are the most commonly used piezoelectric “hard” materials. Especially PZT8 is considered a harder material due to its high mechanical quality factor Qm and is a better choice for resonant devices. PZT4 is used in signal transmissions such as sonar, underwater acoustic transmitter.
The mixed oxide method or the columbite precursor method can be used to produce these polycrystalline ceramics. In the mixed oxide method, PbO, ZrO2, TiO2, Nb2O5, ZnO, MnO2 and NiO oxides are mixed in certain proportions to form the desired product composition and powder is prepared. After the powder mixture is prepared, zirconium oxide balls and isopropyl alcohol are rotated in a ball mill for 24 hours to mix. Then the thoroughly mixed powder mixture is dried at 80 ° C for 10 hours. After drying, the mixture is calcined in an alumina crucible at 850 ° C for 4 hours. The calcined powders are ground again with zirconium oxide balls, but this time in an aqueous medium and using a dispersant solution for 24 hours. The obtained granules are exposed to pressure with the help of a hydraulic press and shaped into disc shaped tablets. The shaped samples are sintered in the alumina crucible at 1000-1100 ° C for 2 hours. With the sintering process, the product takes the structure of polycrystalline ceramic. Following sintering, the surfaces of the samples are finalized by machine grinding, polishing with lapping, polishing and cutting. The product is coated with a conductive paste and kept at high temperature for a short time, creating a permanent conductive surface. Thus, it is ensured that the surface coating is within the specified tolerances. Ceramic samples are subjected to polarization process in an oil bath at 120 ° C under an electric field of 24 kV / cm for 15 minutes. Thus, a bipolar direction is formed in the ceramic.
Before the dielectric and piezoelectric properties are measured in the last step, the product is left for 24 hours. At the end of this period, dielectric properties are measured with the help of impedance / gain analyzer. Piezoelectric charge constant (d33) measurement is performed with semi-static piezoelectric d33 meters. The phase structures of sintered samples are examined by X-ray diffraction, Cu Kα radiation and graphite using a monochromator. The microstructure of the samples, on the other hand, is examined by taking images from the broken surfaces with a 5-20 kV operating voltage using a scanning electron microscope. In this way, after the product is tested with various parameters, the data are recorded and the desired parameters are determined according to the area of use.
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