Preparation And Piezoelectric Properties Of Piezoelectric Materials For Manufacturing Piezoelectric Transformer

Piezoelectric ceramic material is an important functional ceramic material,which can realize the conversion between the mechanical energy and electrical energy,and is widely used in mechanism,electrics and telecommunication.At present,there are two types of piezoelectric ceramics,they are lead oxide-based piezoelectric ceramic materials and lead-free piezoelectric materials.The lead contents of lead oxide-based piezoelectric ceramic materials are more than 60%.When they are sintered in high-temperature they will produce environment pollution by lead volatile.However,lead oxide-based piezoelectric ceramic materials are still difficult to be substituted due to their excellent performance and the poor performance of lead-free piezoelectric ceramic materials in the practical application,so lead oxide-based piezoelectric ceramic materials have a lot of exploration space.In order to obtain high conversion efficiency and high step-up ratio of voltage, piezoelectric materials suitable for application in piezoelectric transformers should have high mechanical quality factor(Q_m),high electromechanical coupling factor(K_p),high piezoelectric constant(d₃₃),and low dielectric loss(tanδ). Pb(Zn_1/3Nb_2/3)_0.20(Zr_0.52Ti_0.48)_0.80O₃+xMnO₂ piezoelectric ceramics were prepared using columbite precursor method.The effects of the addition of MnO₂ on crystallographic phase and electromechanical properties were investigated.The results showed that the pure perovskite structure nearly by the morphotropic phase boundary(MPB) was obtained at sintering of 1200℃for 2 h.With the increasing of MnO₂ content,the piezoelectric constant d₃₃ and electromechanical coupling factor K_p increase,then decrease.When the mass content of MnO₂ is 0.2 wt.%,the largest d₃₃ and K_p were obtained,they are 250 PC/N and 0.52,respectively.Moreover,the dielectric loss tanδdecreases and the mechanical quality factor Q_m increases with the increasing of MnO₂. When the mass content of MnO₂ is 0.5 wt.%,the smallest tanδand the largest Q_m were obtained,they are 0.0046 and 1434,respectively.The above result shows that the piezoelectric constant and electromechanical coupling factor are not enough good.We hope to improve the piezoelectric constant and electromechanical coupling factor through doping a soft doping agent.Sb₂O₃ was chosen as the soft doping agent.The PZN-PZT ternary system owns high stability and compactness and will offer a high electromechanical coupling factor and high piezoelectric constant after the addition of Sb₂O₃.The result shows that after the addition of Sb₂O₃,the piezoelectric constant and the electromechanical coupling factor have been improved from 250 PC/N to 302 PC/N,0.52 to 0.60,respectively.In addition,we also discussed the design method of piezoelectric transformer,and a piezoelectric transformer was designed combining with the practice.