| Piezoelectric energy harvesting,as a new type of energy harvesting conversion technology,has become a research hotspot in the field of new energy.Especially in some high temperature extreme fields,such as aerospace,energy exploration,automobile manufacturing,etc.,the high temperature power supply of micro-devices such as sensors has been severely challenged.Such as active fuel injection nozzles,internal combustion engines,nuclear reactors and other important parts of self-testing,sensing and communication,the operating temperature is as high as 200?300°C,or even higher,and it is imminent to realize the self-power supply of micro-devices in extreme environments of high temperature.Energy harvesting based on piezoceramics may be considered an effective solution to replace the traditional batteries and provide a long-term power supply for high temperature micro-devices.And the research of high temperature piezoceramics used in energy harvesting is of great significance to further promote the practical application of high temperature piezoelectric devices.The essential factors for high temperature piezoelectric energy harvesting materials are high Curie temperature,high depolarization temperature and high piezoelectric property.These macroscopic properties at high temperatures are mainly due to the crystal structure,phase composition and domain configuration of the material at high temperatures.In-depth study of the evolution of the crystal structure,phase composition and domain configuration of materials under different temperature fields,and analyze of the intrinsic relationship between the macroscopic properties and microstructure of materials at high temperatures,are the keys to constructing high temperature piezoelectric energy harvesting materials.In this work,0.36Bi Sc O3-0.64Pb Ti O3was selected as the matrix material,guided by the concepts of phase boundary design and crystal structure modulation,by introducing the third component to adjust the performance,and then high temperature piezoceramics with high performance are finally obtained.Combining multiple in situ technologies reveals the intrinsic relationship between microstructure and macroscopic performance,and provides a reference for the design and preparation of high temperature piezoceramics.Furthermore,the piezoceramics were assembled into a cantilever type piezoelectric energy harvester,and the high temperature power generation performance from room temperature to 450? has been evaluated,which directly show the application potential in the field of high temperature energy harvesting.The main results are as follows:Firstly,taking four representative piezoceramics(0.94(Na0.5Bi0.5)Ti O3-0.06Ba Ti O3,0.2Pb(Zn1/3Nb2/3)O3-0.8Pb(Zr0.5Ti0.5)O3,0.36Bi Sc O3-0.64Pb Ti O3and Ba0.85Ca0.15Ti0.9Zr0.1O3)as an example,by using a designed in situ Berlincourt-type high temperature d33meter,combined with variable temperature XRD and dielectric temperature spectrum test,it was confirmed the depolarization behavior is directly related to the structural phase transition.Finally,0.36Bi Sc O3-0.64Pb Ti O3,which has the best comprehensive performance,was determined as a high temperature piezoelectric energy harvesting material for further research.Based on this,the relationship between the composition,microstructure and electrical properties of(1-x)Bi Sc O3-x Pb Ti O3system was systematically studied.The best electrical properties were obtained at morphotropic phase boundary(MPB)of x=0.64.The effects of the synergistic effect between piezoelectric charge constant(d33)and dielectric constant(?r)on the stability of the working temperature of the high temperature piezoelectric energy harvesting material are discussed.In the mode of the cantilever type energy harvester assembled by this composition,a stable output voltage was obtained with fluctuations belową20%over a broad temperature range of 100?250?.The good temperature stability shows its potential industrial application prospect in the field of high temperature piezoelectric energy harvesting.Secondly,with the aim of further increase the Curie temperature(Tc)and widen the operating temperature range,the 0.36((1-x)Bi Sc O3-x Bi Fe O3)-0.64Pb Ti O3 system was constructed by introducing Bi Fe O3 with a high Curie temperature.The research results of the association mechanisms between electrical performance and microstructure show that:low-melting Bi Fe O3 plays a role as a sintering aid,lowering the sintering temperature of the ceramic and increasing the grain size.At the same time,the crystal structure shifts from the initial MPB with rhombohedral and tetragonal phase coexistence to the tetragonal phase side,and the Tc increased gradually with increasing Bi Fe O3content.Under the conventional air atmosphere sintering conditions,the Tc of the specimen with x=0.3 can reach?500?,and the d33is 125 p C/N.Compared with that,the d33of the same composition specimen sintered in an oxygen atmosphere is increased to 165 p C/N,which is mainly due to the decrease in the content of oxygen vacancies that helps to increase poling electrical field.Further optimization of the process,the quenching strategy effectively reduced the oxygen vacancy concentration,and at the same time,the domain configuration was adjusted by freezing the high temperature Fe Bi5Ti3O15 mesophase.Finally,d33 was increased to 151 p C/N,which is21%higher than that of conventional sintered counterpart.The process provides valuable indications to conquer main challenges for the Bi Fe O3-containing piezoceramics applications.The quenched ceramic specimen was assembled into a cantilever beam energy harvester.At a high temperature of 300? and 1g acceleration,the open circuit voltage is 1.58 V,and the maximum output power is 0.073?W,which can charge 0.23 V of a 10?F,16 V commercial electrolytic capacitor in 100 s.Most importantly,there is still an electrical signal output at 450?,which directly shows its potential application in high temperature extreme environment.Furthermore,in order to obtain high temperature piezoceramics with both high piezoelectric properties and excellent temperature stability,a new ternary system of x Pb(In1/2Nb1/2)O3-y Bi Sc O3-z Pb Ti O3was constructed based on the phase boundary design.Aiming to achieve high temperature piezoceramics with excellent comprehensive properties through the multiple MPBs in the ternary system.MPB specimen has the highest piezoelectric property at x=0.03,y=0.35,z=0.62,with d33value of 492 p C/N and a Tc of 413°C.Its cantilever type piezoelectric energy harvester has an open circuit output voltage of 9.44 V and a power density of 0.21?W/mm3 at a high temperature of 350?,which can charge 3.66 V of a 10?F,16 V commercial electrolytic capacitor in 60 s.The power can fully meet the work of conventional low-power microsensors,which fully shows its excellent high temperature power generation capability.MPB specimen has the best comprehensive high temperature piezoelectric property at x=0.04,y=0.345,z=0.615,with d33 value of 478 p C/N at 200°C,meanwhile,the fluctuation of d33 is less thaną10%over an ultra-broad temperature range of 50?350°C.Combining a variety of in situ technical characterization and piezoelectric theory analysis reveals that the characteristic hierarchical domain configuration in MPB is helpful for obtaining high piezoelectric property and high temperature stability at the same time.Its cantilever type piezoelectric energy harvester also has excellent temperature stability,which can achieve a wide temperature stable charging task from 25 to 350°C,showing potential applications as a high temperature piezoelectric energy harvester.Finally,guidde by crystal structure modulation,the z Bi Sc O3-x Pb Ti O3-y Bi(Zn0.5Hf0.5)O3system was constructed by introducing Bi(Zn0.5Hf0.5)O3with high tetragonality.The purpose is to maintain the asymmetry at high temperature by increasing the distortion of the crystal structure,so as to obtain the high piezoelectric property at high temperature.The results show that the MPB specimen with x=0.635,y=0.01,z=0.355 has a large lattice distortion and a large number of domains at a high temperature of 400°C.Its in situ d33 value is 726 p C/N,which is 321 p C/N higher than the d33 of the substrate 0.36Bi Sc O3-0.64Pb Ti O3at this temperature(405 p C/N).Even at 500?,the specimen still has piezoelectric charge constant of 503 p C/N.Correspondingly,the piezoelectric energy harvester made with it still has a standard,stable sine waves output electrical signal at a high temperature of 400?,and the open circuit voltage is as high as 3.16 V,and a power density of 0.031?W/mm3 at a high temperature of 400?,which can charge 0.9 V of a 10?F,16 V commercial electrolytic capacitor in 40 s.It fully shows its great potential in the field of high temperature self-powered.From the perspective of material design,this work characterizes the high temperature electrical properties and crystal structure of materials.Combined with a variety of in situ techniques,the intrinsic correlation mechanism between the electrical properties of materials and microstructures such as crystal structure,phase composition,and domain configuration was systematically analyzed,and has a guiding effect on the construction of high-performance high temperature piezoceramics.Based on this,the high temperature piezoelectric energy harvesting performance of piezoceramics was systematically evaluated,and the research goal of combining materials and devices was achieved.It provided a solid theoretical and application basis for the development of high temperature piezoelectric energy harvesting. |
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