Preparation And Properties Of NBT-KBT-BT Ternary Lead-free Piezoelectric Ceramics

In this paper,the（1-2n）NBT-nKBT-nBT lead-free piezoelectric ceramics and Li⁺,Mn²⁺,and Co³⁺-doped NKBT4 ceramics were prepared by the solid-phase synthesis method.The quasi-homophases of ceramics were determined by X-ray diffraction measurements of the ceramics synthesized in this paper.The influence of the world and the doped ions on the ceramic phase structure,but also for all ceramics have been tested for piezoelectric performance,variable temperature hysteresis loop test and temperature change dielectric properties under different frequencies.Get the following conclusions:（1）X-ray diffraction analysis of（1-2n）NBT-nKBT-nBT ceramics shows that the ceramic system has a quasi-homogeneous trigonal and tetragonal phase boundary between n=0.04⁰.08;The XRD pattern analysis of Li⁺,Mn²⁺,and Co³⁺-doped NKBT4 ceramics shows that these three ions do not change the type structure of NKBT4 ceramics.The SEM images of（1-2n）NBT-nKBT-nBT ceramics show that the introduction of KBT and BT will reduce the grain size of the ceramic.The SEM images of Li⁺,Mn²⁺and Co³⁺doped NKBT4 ceramics show that the introduction of these three ions will increase the grain size of the ceramic.（2）After analyzing the dielectric-temperature spectra of（1-2n）NBT-nKBT-nBT ceramics and NKBT4-xLi ceramics,it was found that there are two dielectric peaks and one dielectric loss peak during ceramic heating.And the ferroelectric phase-ferroelectric phase-paraelectric phase transition has occurred.（1-2n）NBT-nKBT-nBT ceramics have a maximum dielectric constant of 1715 at room temperature at n=0.06,and a minimum dielectric loss of 4.3%at room temperature at n=0.04.Moreover,the dielectric loss test results show that Li+does not significantlyreducethedielectriclossofNKBT4ceramics.The dielectric-temperature spectrum analysis of NKBT4-yMn ceramics and NKBT4-zCo ceramics shows that the dielectric temperature spectra of ceramics have two dielectric anomalies when the Mn²⁺and Co³⁺contents are low.When the content of Mn²⁺and Co³⁺increases,there is only one dielectric peak in the dielectric temperature of the ceramic.The best dielectric properties of NKBT4-yMn ceramics is that the maximum dielectric constant at room temperature is 1662 at y=0.2 mol.%,and the minimum dielectric loss is 2.4%when y=1.0 mol.%.The NKBT4-zCo ceramic has a minimum dielectric loss of 1.48%at z=1.0 mol.%.（3）Using the modified Curie-Weiss Law to fit the ceramics involved in this study,it was found that the diffusion coefficients of ceramics are all between 1 and 2,indicating that the ceramics involved in this paper are all relaxed irons.Electrical body.This is mainly due to the fact that the A-site of the ceramic is a complex perovskite structure that is replaced by a variety of ions,and there is an uneven distribution of components on the nanometer scale,which causes the ceramic to have a relaxed characteristic.（4）Analysis of hysteresis loops of NKBT4-xLi ceramics,NKBT4-yMn ceramics and NKBT4-zCo ceramics shows that Li⁺,Mn²⁺,and Co³⁺can all increase the remanent polarization of NKBT4 ceramics while reducing the coercive field at room temperature.Among them,Mn²⁺has the greatest influence on NKBT4 ceramics,and the maximum remanent polarization and the minimum coercive field of the system ceramics are obtained at y=0.6 mol.%at room temperature,which are Pr=48.93μC/cm² and E_c=3.47 kV/mm,respectively.（5）Maximum piezoelectric constant and electromechanical coupling coefficient of（1-2n）NBT-nKBT-nBT ceramics at n=0.08,146pC/N and 26.5%respectively.The ceramic has a maximum mechanical quality factor of 287 at n=0.04.The piezoelectric performance analysis of Li⁺,Mn²⁺and Co³⁺-doped NKBT4 ceramics shows that these three ions can improve the piezoelectric performance of ceramics.This may be due to the fact that small-radius ions displace the larger-radius ions in the ceramic lattice,causing distortion of the ceramic lattice,and the electrical domain transformation is more likely to occur,thus increasing the remanent polarization and piezoelectric properties of the ceramic.