Performance Optimization And Energy Harvesting Simulation Of BiScO₃-PbTiO₃ High-temperature Piezoelectric Ceramics

As a class of functional electronic materials that can directly realize the effective conversion of mechanical and electrical energy,piezoelectric materials are widely used in mechanical manufacturing,electronic communication,military and other fields,and have broad application prospects in functional conversion devices such as force,heat,light,electricity and magnetism.For example,the electric injection device of the automobile internal combustion engine requires piezoelectric materials to work stably in a high temperature environment of 200℃or even 300℃or more,etc.The research on high temperature piezoelectric materials and their devices for high temperature applications has received unprecedented attention.High Curie temperature,high depolarisation temperature and high voltage electrical properties are essential elements as high temperature piezoelectric energy harvesting materials.These macroscopic properties are reflected in the internal crystal structure,phase composition and microscopic morphology of the material,therefore dissecting the intrinsic correlation between the macroscopic properties and the internal microstructure of the material is the key to developing high temperature piezoelectric energy harvesting.Currently,commercial piezoelectric materials are mainly Pb（Zr,Ti）O₃（PZT for short）piezoelectric ceramic materials,but as the normal operating temperature range is limited to below150°C and cannot operate stably in higher temperature environments,the search for piezoelectric materials with high Curie temperatures and excellent properties has become a growing and urgent need.The thesis selects the partial tripartite component 0.39Bi Sc O₃-0.61Pb Ti O₃（0.39BS-0.61PT）piezoelectric ceramics as the research object to achieve the optimization of ceramic properties from two aspects.The first is to improve the piezoelectric properties of the ceramics through ion doping;the second is to induce the transition of the phase structure of the ceramics to the MPB phase boundary based on the theory of lattice distortion regulation of phase boundaries to achieve the optimal tetragonal phase（T-phase）ratio and increase the Curie temperature while improving the electrical properties.Finally,the design and simulation of a piezoelectric cantilever beam vibration energy harvester using a 0.39BS-0.61PT piezoelectric ceramic with optimised properties is carried out to explore the potential of BS-PT-based piezoelectric materials for energy harvester applications.（1）Ceramics with different Sm contents of 0.39Bi Sc O₃-0.61(Pb_1-1.5xSmx)Ti O₃（xSm-0.39BS-0.61PT）（x=0,0.005,0.01,0.015mol）were prepared by solid-phase reaction method.XRD phase structure analysis showed that Sm³⁺substitution at the A-site contributed to the gradual shift of the ceramic phase structure from a single tripartite phase.XRD phase structure analysis shows that Sm³⁺replaces the A position,which makes the ceramic phase structure gradually change from a single tripartite phase to a tetragonal phase,and realizes the construction of quasi-homomorphic phase boundary structure.The electrical performance test shows that with the increase of Sm³⁺content,the change rate of piezoelectric constant d₃₃ and dielectric constant_ron the tetramonal side is different,and the excellent electromechanical conversion performance of n ceramics is successfully obtained.When the sintering temperature is 1150℃and the Sm³⁺doping content is x=0.01,the electrical properties of the ceramics are the best:d₃₃=455p C/N,k_p=55%,_r=1075,tanδ=0.046 and T_c=382°C.Temperature stability tests show that xSm-0.39BS-0.61PT ceramics exhibit excellent piezoelectric stability from room temperature to 290℃.（2）The solid phase method was used to prepare y Zn O-0.39Bi Sc O₃-0.61Pb Ti O₃（y Zn-0.39BS-0.61PT）（y=0.005,0.01,0.015,0.02mol）ceramics.XRD analysis showed With the increase of Zn O content,the phase structure of the ceramics gradually changes from a single tripartite phase to a tetragonal phase,and the quasi-homomorphic phase boundary construction is realized.The electrical properties show that the piezoelectric constant d₃₃ increases and then decreases as the Zn O content increases,and the Curie temperature keeps moving towards the high temperature.At y=0.015,with a T-phase ratio of about 70%,the best overall performance is obtained for this component ceramic:d₃₃=431p C/N,k_p=53%,_r=1285,tanδ=0.047,T_c=432°C,and the ceramic shows good piezoelectric stability from room temperature to 365°C.（3）A piezoelectric cantilever beam type vibration energy harvester was designed using0.01Sm-0.39BS-0.61PT high temperature piezoelectric ceramics.A set of self-consistent full-matrix macroscopic electromechanical parameters was obtained.The energy harvester was modelled and simulated using COMSOL Multiphysics finite element simulation software.The results show that the cantilever beam vibrates periodically up and down at the same frequency of66Hz and generates a potential difference in the upper and lower ceramic plates,which generates a current when connected to an external load.The output voltage and output electrical power of this energy harvester increases and then decreases with increasing frequency,in a symmetrical distribution.When the frequency is 66Hz,the load resistance is 12kΩand the acceleration is 1g,the output voltage is 5.589 V and the output electrical power is 1.302m W.The electromechanical conversion efficiency of the 0.01Sm-0.39BS-0.61PT ceramic is 98.64%.The study of the relationship between this energy harvester and the external load showed that the output voltage showed an increasing trend with the increase of the external load and was stable at 7.012V;the output electric power showed a symmetrical decreasing trend with the increase of the resistance value and reached the maximum value of 1.349 m W at the resistance value of 10kΩ.The study of the relationship between this energy harvester and the external excitation acceleration showed that the output The relationship between the output voltage and the external excitation acceleration shows that the output voltage increases linearly with the acceleration and the output power increases quadratically with the acceleration.Varying the height of the center of mass of the block reduces the characteristic frequency of the energy harvester and improves the output characteristics of the energy harvester,optimising the harvesting efficiency of the energy harvester.