取向多孔钛酸钡基陶瓷的介电与压电性能

Dielectric and piezoelectric performance of aligned porous BaTiO3-based ceramic

采用冷冻浇注法制备取向多孔0.5Ba(Ti0.8Zr0.2)O3−0.5(Ba0.7Ca0.3)TiO3(BCZT)压电陶瓷。研究结果表明:制得的压电陶瓷材料孔隙率为18%~44%,取向孔道的层间距随孔隙率的减少而增加,最大为25μm。由于电场局部集中,相同电场条件极化后的取向多孔BCZT整体极化效率降低,因此,剩余极化强度随孔隙率的增加而降低,适量的孔隙(孔隙率<20%)有利于电畴翻转降低矫顽场,孔隙数的增加会提高未极化区域,从而提高矫顽场。取向多孔BCZT陶瓷的相对介电常数随频率增加而降低,当孔隙率从18%增加到44%时,相对介电常数从1806降低到1097,介电损耗从0.008升高到0.014,居里温度随孔隙率增加从致密体的106℃增大到119℃。静水压电荷系数dh却随着孔隙率的增加从33 pC/N增加到148 pC/N,由于多孔结构介电常数随孔隙率增加而降低,大幅提高了静水压电压系数gh和静水压优值dh·gh,gh从3.8 mV∙m/N提高到14.7 mV∙m/N,dh·gh从0.14×10^−12 m^2/N提高到2.17×10−12 m^2/N。取向多孔BCZT陶瓷具有与铅基压电材料相当的压电性能,在压电传感器、压电水声换能器等领域具有巨大的应用潜力。

Porous 0.5Ba(Ti0.8Zr0.2)O3−0.5(Ba0.7Ca0.3)TiO3(BCZT)lead−free ceramics were produced by freeze casting with the porosities range of 18%−44%.The results show that the width between the adjacent lamellar layers increased with the decreas of the porosity with the maximum value of 25μm.Due to the inhomogeneous field distribution in the porous BCZT,the remnant polarisation decreases with the increase of the porosity under the same poling condition.The proper porosity(<20%)is beneficial to the rotation of the domain,therefore leading to the lower coercive field.However,further increasing the porosity increases the amount of the unpoled areas,resulting in the higher coercive field.The relative permittivity reduces from 1806 to 1097 when the porosity increase from 18%to 44%,while the dielectric loss increases from 0.008 to 0.014 and the Curie temperature increases from 106℃to 119℃.Hydrostatic charge coefficient dh increases from 33 pC/N to 148 pC/N.Due to the greatly reduced relative permittivity,the corresponding hydrostatic voltage coefficient gh and hydrostatic figure-ofmerit dh·gh apparently increase,e.g.gh increases from 3.8 mV·m/N to 14.7 mV·m/N and dh·gh increases from 0.14×10^−12 m^2/N to 2.17×10^−12 m^2/N.Therefore,the aligned porous BCZT ceramic with the comparable piezozelctric performance and the lead-based piezoelectric materials has many great potential practical transducer applications such as piezoelectric sensors and transducers.