| As one kind of important functional materials,piezoelectric ceramics can realize the conversion of mechanical energy and electrical energy.Due to the excellent piezoelectric properties,lead-based piezoelectric ceramics with perovskite structure based on PbTiO3-PbZrO3(PZT)have been widely used for sensors,actuators and ultrasonic transducers.However,increasing health and environmental concerns about the toxicity of lead in PZT ceramic materials have stimulated the search for high-performance lead-free piezoelectric materials.With the rapid progress of modern science and technology,the development tendencies of electronic devices are integration,multi-functionalization and environmental protection.This requires that electronic devices should have the ability to simultaneously and quickly respond to electric,mechanical and optical stimuli of the external environment,promoting the research and development of lead-free multifunctional materials.In this paper,following works are carried out:Firstly,the ferroelectric composites of Er:0.94Bi0.5Na0.5TiO3-0.06BaTiO3/xZnO(Er:BNTBT/xZnO,x = 0,0.1,0.2,0.3,0.4)were prepared by the solid state reaction method and the mole ratio of Er3+ to BNTBT is 1.0%.The composite structure is verified by powder X-Ray Diffraction(XRD)and Scanning Electron Microscopy(SEM)measurements and Er3+ ions have entered into the lattice of BNTBT.The green and red photoluminescence intensities increase monotonously with increasing ZnO content and the green photoluminescence intensity of the x = 0.4 unpoled sample is 4.5 times larger than that of x = 0.Further,the poling process suppresses the photoluminescence of Er:BNTBT(x = 0),while it enhances the green photoluminescence of other samples(x>0)significantly.Temperature-dependent dielectric constant and loss show that Er:BNTBT/xZnO ceramics are relaxor ferroelectrics,and the depolarization is suppressed when x>0.At room temperature,all of the ceramics possess ferroelectric nature and the ferro-/piezoelectric properties tend to weaken with increasing x.The ferroelectric property measurement at different temperatures confirms the thermal depolarization is suppressed after introducing ZnO and x>0 samples show excellent temperature stability of the ferroelectric property.These results not only provide a hybrid method to significantly enhance and in-situ tune the photoluminescence of lanthanide ions,but also are helpful for developing multifunctional materials with excellent optical and electrical properties simultaneously.Secondly,the ferroelectric composites of((Bi0.5(Na0.84K0.16)0.5)0.96Sr0.04)(Ti0.975Nb0.025)O3/xZnO(BNT-2.5Nb/xZnO,x = 0,0.1,0.2,0.3,0.4)were prepared by the solid state reaction method.XRD and SEM measurements show that the composite structure is formed within BNT-2.5Nb/xZnO.The nano-sized ZnO locates at the boundaries between BNT-2.5Nb grains and grows into larger ZnO particles.Temperature-dependent dielectric constant and loss show that BNT-2.5Nb/xZnO ceramics are relaxor ferroelectrics,and the depolarization is suppressed when x ? 0.2.Complex impedance spectra measured at 460??560?indicate the nonsignificant difference of thermally activated electrical characteristics between grains and grain boundaries,and the resistance of all the ceramics exhibits a negative temperature coefficient.For all samples,the activation energies(Ea)for electrical conduction fitted by using the Arrhenius equation are all less than 2eV,indicating that the oxygen vacancies play an important role in the ions hopping conduction of all the samples at high temperatures.At room temperature,all of the ceramics possess ferroelectric nature and the ferro-/piezoelectric properties tend to strengthen with increasing x.The piezoelectric property measurement at different temperatures indicates the thermal depolarization is suppressed after introducing ZnO.Our results not only provide a feasible way to tune electrical properties of BNT-based incipient ferroelectrics,but also may stimulate further work on artificially-structured high performance ferroelectrics. |
PDF Full Text Request