Study On (K,Na) NbO3-Based Piezoelectric Electric Ceramic And Its Application In Vibration Energy Harvester

Nowadays,with the development of net of thing and wearable device,it is more and more difficult and inconvenient for traditional chemistry batteries to be as power supply.Moreover,we face the challenge of increasingly serious energy crisis.Fortunately,there are large number of vibrations in our environment and we can collect these energy for our use.This research is just focused on this,based on the piezoelectric effect of piezoelectric materials,design energy harvesters to collect vibration energy and translate them to electric energy to power electronic component.This study is mainly to improve the piezoelectric properties of piezoelectric materials.We also made simple device models and tested the performance of them.At present,piezoelectric ceramics occupy large percentage of the piezoelectric materials in use.And among them,lead-piezoelectric ceramic is of the most widely use.However,lead content of these ceramic is over 60%,which is a big threaten to the human beings and environment.Because of the above reasons,Lead free piezoelectric ceramic has attracted more and more attention.Potassium sodium niobate based lead-free piezoelectric ceramics(KNN),with excellent piezoelectric properties,is considered to be the most promising alternative to lead-piezoelectric ceramic.While,it is very difficult to get ceramic with high density through traditional sintering.At the same time,the improvement of its performance has been greatly restricted.In this study,we try to improve the piezoelectric properties of KNN by two means.One is to improve the preparation technology,and the other way is composition modification.A twice calcination–milling processure was introduced in the preparation of KNN pre-sintered powders.By this way,the piezoelectric properties of the ceramic had Significant improvement and better than most of the reported values.The relative density was 96.9%,electromechanical coupling factor(kp)was 0.44,piezoelectric constant d33 was 111PC/N.while the dielectric loss tan? was only 0.85%.The method does not require specialized equipment,economically and simply,being suitable for large-scale industrial production.In the composition modification method,we introduced x mol% CuO by three different ways to find the value of x and the heat treatment process,by which we could get the most excellent piezoelectric properties.They are:(1)Mixing CuO as B-site with other components directly.When x =0.5,and the sintering temperature was 1090?,the ceramic performed best,d33 was 98 PC/N,tan? was 0.1%,Qm was 486,and kp was still maintained at the higher value of 0.43;(2)Synthetizing CuO and Nb2O5 to be precursor before adding other components.When x=0.5,sintering temperature was 1100?,it was found that the ceramic had excellent properties,d33 was 97 PC/N,tan? was 0.23%,Qm was 669,and kp was 0.42;(3)Adding Cu O as sintering aid,it was still when x=0.5,the material performed best,Qm was up to 944,and kp was 0.36,the sintering temperature was 1075?.The energy harvester was made by the KNN ceramic added 0.5mol% CuO as sintering aid.The resonance frequency of the harvester was 41.6Hz,the Optimum load was 21.25M?,when the acceleration was 2.25m/s2,the output voltage was 15.3V,and the output power was 5.8?W.