| PZT-based piezoelectric ceramics have been widely used in ultrasonic motors and ceramic transformers and so on,where excellent performances are required.Main features are miniaturization,integration and high-power.However,an efficient decrease of sintering temperature by means of doping sintering aids is generally at the expense of piezoelectric and electromechanical properties.The important development direction of high-power piezoelectric materials is simultaneously sintering at low-temperature and obtaining excellent performances.In this thesis,a novel PZT-Bi Mn BO3-PZN quaternary high-power piezoelectric ceramic was successfully prepared via a conventional solid-state reaction.The phase structure,ferroelectric,piezoelectric and dielectric properties of the MPB before and after doping were studied.Firstly,the effects of BMn T substitution content and Zr/Ti ratio on the sintering temperature,microstructure and electrical properties of 0.9PxZT-y BMn T-（0.1-y）PZN ceramics were investigated.It was found that as the substitution content of BMn T increased,the trigonality of the ceramic increased and the sintering temperature decreased.The sample which sintered at 1120 ℃ with y=0.04 possessed the best comprehensive performances:εT33/ε0=1454,d33=310 p C/N,kp=0.56,Qm=1149,tanδ=0.39%,Tc=322 ℃.The MPB was found by changing the Zr/Ti ratio.The piezoelectric activity was the highest in the vicinity of MPB.The grains of all the samples developed well,and the density reached 97%.The samples with x=0.50possessed the best comprehensive performances.Secondly,the effects of the relative contents of metal oxides Fe2O3 and Cu O on the sintering temperature and electrical properties of ceramic materials were investigated.The sintering temperature of the ceramic decreased with increasing doping amount of Fe2O3,and the electrical properties were improved.The sample which sintered at 1020℃ with y=0.07 possessed the best comprehensive performances:ρR=98%,εT33/ε0=1751,d33=385 p C/N,kp=0.62,Qm=1150,tanδ=0.31%,Tc=321 ℃.Finally,PZT-BMn S-PZN quaternary high-power piezoelectric ceramics were prepared via a conventional solid-state reaction due to the high Curie temperature and high Qm of BMn S.Phase transformation,microstructure,ferroelectric properties,piezoelectric and dielectric properties near the MPB were studied.It was found that the phase structure changed from tetragonal to rhombohedral with the increasing of Zr/Ti ratio.The grain size was uniform,and grains were well compacted.Microstructures were free of porosity.The sample which sintered at 1120 ℃ with Zr/Ti=0.48/0.52possessed the best comprehensive performances:ρR=97%,εT33/ε0=1450,d33=285 p C/N,kp=0.53,Qm=1525,tanδ=0.76%,Tc=297 ℃.By adding the metal oxide Fe2O3,the sintering temperature of the ceramic material was further lowered to 1040°C,and the average particle diameter was increased.The densification of the ceramic was promoted.The piezoelectric and electromechanical properties were improved.The purpose of optimizing performance and low temperature sintering was achieved.The material had a lower sintering temperature than conventional PZT-based high-power piezoelectric ceramics.The sample which sintered at 1040 ℃ with y=0.7 possessed the best comprehensive performances:ρR=98%,εT33/ε0=1615,d33=305 p C/N,kp=0.56,Qm=1678,Tc=302 ℃.Compared with traditional piezoelectric ceramics,the composition in the current research has low sintering temperature and excellent piezoelectric performance,indicating that it can meet the requirements of low cost and practicality of high-power devices. |
