Preparation And Properties Of BFO,PZT Based Piezoelectric Ceramics And PZT Based Multilayer Piezoelectric Ceramic Actuator

In this dissertation,the comprehensive study of two ceramic systems(1-x)BiFeO3-xBi0.5K0.5TiO3(abbreviated as(1-x)BFO-xBKT)and Pb0.92Sr0.06Ba0.02(Mg1/3Nb2/3)0.25Ti0.40Zr0.35O3(abbreviated as PMN-PZT)was performed.Both types of ceramic were prepared by conventional solid-state reaction method.By adding a certain amount of CuO in the PMN-PZT raw material,the sintering tempe rature of the ceramics was decreased significantly.The piezoelectric actuator with PMN-PZT/Ag multilayer structure was fabricated at 900 ?,and compared with the adhesive bonding method.(1-x)BFO-xBKT ceramics were synthesized by conventional solid-state reaction method to study the influence of BKT content on the structural and electrical properties.At x=0.4,the morphologic phase boundary(MPB)of rhombohedral-tetragonal was achieved.For 0.6BFO-0.4BKT the ceramic showed the piezoelectric constant(d33)up to 61 pC/N.The Curie temperature of the 0.6BFO-0.4BKT ceramic was-458 ?.The results show that the 0.6BFO-0.4BKT ceramic has great potential to be utilized in the fabrication of actuators for high temperature environment.Secondly,PMN-PZT ceramics were prepared by the conventional solid-state reaction method,and the effect of sintering temperature on the structural and electrical properties of PMN-PZT ceramics was also explored.The ceramic sintered at 1250 ?has shown the best electrical properties,and high d33 of?690 pC/N.The measured Curie temperature of the ceramic was?200 ?.As the PMN-PZT ceramic has shown the high piezoelectric constant but was prepared at high sintering temperature,hence it was decided to explore the method to lower its sintering temperature.Appropriate CuO addition was performed in PMN-PZT depending on molar concentration of PMN-PZT ceramics.The 0.7wt%CuO has decreased the sintering temperature of PMN-PZT from 1250 ? to 900 ?.PMN-PZT:0.7wt%CuO ceramic has recorded a high d33 value of 630 pC/N,and a larger strain of 0.28%under the electric field of 40 kV/cm.These properties prove that PMN-PZT:0.7wt%CuO ceramic has great potential for the fabrication of large displacement actuator.Finally,the PMN-PZT:0.7wt%CuO component is used to prepare actuator by low temperature co-fired method and with adhesive bonding method for comparison.The results showed that by low temperature co-fired method,the piezoelectric ceramic unit and the silver layer is in good condition,there is no large defect and the thickness of the piezoelectric ceramic unit is uniform(each unit is about 70 ?m).Inner electrode layer has uniform thickness.The actuator's longitudinal length is 1.98 mm and cross section area is 7.27×10.05 mm.The displacement of the actuator is 2.24 ?m under the voltage of 150 V,about 0.11%of the longitudinal length and the thrust is-2.7 kN.The actuator prepared by the adhesive bonding method has 20.01 mm longitudinal length and 7.67×6.22 mm cross section area.The displacement of the actuator is?17.9 ?m under the voltage of 150 V,about 0.089%of the longitudinal length and the thrust is?3 kN.In a word,study of(1-x)BFO-xBKT ceramics allows the actuator usage in high temperature environment.While,good properties of the PMN-PZT ceramics have lead us towards the fabrication of PMN-PZT/Ag multilayer actuator,it is expected that our device has the capability to overcome the market demands.