| Lead zirconate titanate(PZT,Pb(ZrxTi1-x)O3)is an important kind of ferroelectric and piezoelectric material in the field of information functional ceramics,and has excellent piezoelectric performance and process stability.It can realize the conversion efficiently between electrical energy and mechanical energy,and exhibites appealing applications in miniaturized and integrated thin film devices.It is worth noting that polycrystalline oriented PZT films show smaller piezoelectric coefficient and lower residual polarization,which restrict their efficient applications in devices.Therefore,it is very important to explore the preparation process conditions for preparing high-performance PZT thin films with preferred orientation,so as to meet the needs of devices.In the present work,PZT thin films with(100)preferred orientation applied to piezoelectric composite vibration plates were fabricated based on RF magnetron sputtering and sol-gel methods.The crystalline orientation,micro-morphology,electrical properties,and fatigue resistance of the films were characterized.The process conditions for preparing PZT piezoelectric films by magnetron sputtering were optimized.The doping modification and multilayered films processes by sol-gel method were studied.In terms of the PZT film applications,the coupled vibration analytical model of piezoelectric composite vibration plate was established.Both PZT/SiO2 and PZT/Cu/SiO2 vibration plates were manufactured and tested.The research contents and results of this work are summarized as follows:(1)The effects of deposition temperature and in-situ annealing temperature of Pt bottom electrode on the grain size and surface morphology of the electrode were studied.The crystalline orientation and microstructure of PZT thin films deposited on different bottom electrodes were analyzed.The results showed that the Pt electrode grown at room temperature after 200℃ in-situ annealing for 30 min was favorable for the growth of(100)oriented PZT films.However,the films with(111)preferred orientation were obtained using the Pt electrodes grown or in-situ annealed at high temperature.Ti content in the Ti-Pt alloy layers-dependent preferred orientation and electrical behaviors of PZT films was investigated.The results showed that the preferred orientation of the PZT films changed from(100)to(111)as the Ti content increased.Maximum peak of(100)and minimum peak of(111)were obtained in the film deposited on Ti-Pt alloy layer with a sputtering power of 12.5 W/150 W,which was attritubuted to the appropriate Ti content.Moreover,this film exhibited the reduced oxygen vacancies concentration,which resulted in a maximum permittivity(εr)and an enhanced remanent polarization(Pr).Ti-Pt alloy bottom electrode would further widen the selection range of PZT film bottom electrodes.(2)The effects of deposition and annealing processes by RF magnetron sputtering on the performances of PZT thin films were investigated.To compensate the Pb loss of PZT thin films,a new method was proposed.By introducing Pb1+x(Zr0.40,Ti0.60)O3 seed layers,Pb loss of post sputtered PZT thin films was compensated,which resulted in an improved(100)preferred orientation in the film with x=0.2.XPS analysis showed that this film exihibited an enhanced piezoelectric constant(d33=105.8 pm/V)because of the reduced oxygen concentration and relieved domain wall pinning.This method has the advantages of well repeatability and simple operation,could provide a practical technology for the preparation of 1μm PZT piezoelectric films by magnetron sputtering.(3)A new process of magnetron sputtering was proposed based on the 0.3Pb(Mg1/3Nb2/3)O3-0.7Pb(Zr0.52Ti0.48)O3/Pb(Zr0.52Ti0.48)O3 heterostructure films.It was found that the film performances depended on both heterogeneous interfaces number and the mode of crystal growth.Because of the highly dense columnar grain and the influence of heterogeneous interface strain,εr and dielectric loss(tanδ)at 0.1 kHz was 1034.9 and 0.039,2Pr reached 21.6 μC/cm2 of the film with five heterogeneous interfaces(H5).At the same time,the piezoelectric constant(e31)of this film reached 8.2 C/m2,which was 3.5 times larger than that of PZT film.(4)Doped PZT piezoelectric films with different concentrations of Eu and La were prepared by Sol-gel method,respectively.The effects of ion concentration on the film texture transition,microstructure,and electrical properties were analyzed.When the Eu doping concentration was 2%,an εr of 1571,a Pr of 20.5 μC/cm2,and a coercive field(Ec)of 41.8 kV/cm were generated in the PEZT film.For film with a Zr/Ti composition of 60/40,the 2%La-doped film exhibited optimal(100)preferred orientation and dielectric property,and the leakage current density at 150 kV/cm was only 8.63×10-8 A/cm2.(5)A new method for the preparation of PZT multilayered film with different lead contents was proposed.The effects of various layer ratios(m/n)of Pb1.25(Zr0.52,Ti0.48)O3 and Pb1.1(Zr0.52,Ti0.48)O3 on the crystalline orientation and electrical properties were investigated.The results showed that the εr reached 1873 at 1 kHz for the film with m/n of 1/3,which was 92%higher than that of Pb1.1(Zr0.52,Ti0.48)O3 film.And the leakage current density was one order of magnitude lower than that of Pb1.25(Zr0.52,Ti0.48)O3 film.The key reason for the improvements in electrical properties is that oxygen vacancies caused by lead loss were suppressesed and domain wall movement was promoted by the stacking sequence of 1/3.(6)The PZT/SiO2 piezoelectric composite vibration plate was fabricated,and the influences of vibration plate with or without ’spring structure’ on the output amplitude were analyzed.Compared to the vibration plate without ’spring structure’,the amplitude was increased effectively and the residual vibration was suppressed by ’spring structure’.The coupled vibration analytical model of piezoelectric composite vibration plate was established,and the influences of the neutral plane position on the equivalent load and output amplitude were analyzed.When the substrate thickness was close to PZT thickness,the neutral plane of the piezoelectric composite vibration plate was located at the contact surface between the substrate and PZT film,which resulted in the significantly increase of the equivalent load and output amplitude.The PZT/Cu/SiO2 composite vibration plate was fabricated.And the vibration test showed that the amplitude of PZT/Cu/SiO2 vibration plate had a double increase compared with that of PZT/SiO2 vibration plate.This coupled vibration analytical model could provide a theoretical basis and process method for the design and fabrication of new piezoelectric composite vibration plates. |
PDF Full Text Request