Limei Zheng

Perovskite (Na0.5K0.5)1−x(LiSb)xNb1−xO3 lead-free piezoceramics

Lead-free potassium sodium niobate piezoelectric ceramics substituted with lithium and antimony (Na0.5K0.5)1−x(LiSb)xNb1−xO3 have been synthesized by conventional solid state sintering method. Compositionally engineered around the orthorhombic-tetragonal polymorphic phase transition, the dielectric and piezoelectric properties were further enhanced with the addition of lithium and antimony substituted into the perovskite structure. The combined effects of lithium and antimony additions resulted in a downward shift in the orthorhombic-tetragonal (TO-T) without significantly reducing TC. The dielectric, piezoelectric, and electromechanical properties were found to be e∕e0>1300, d33>260pC∕N, and kp>50%, while maintaining low dielectric loss. The enhanced polarizability associated with the polymorphic TO-T transition and high TC transition (∼390°C) should provide a wide range of temperature operation.

Complete set of material constants of 0.95(Na0.5Bi0.5)TiO3-0.05BaTiO3 lead-free piezoelectric single crystal and the delineation of extrinsic contributions

Lead-free piezoelectric single crystal 0.95(Na0.5Bi0.5)TiO3 (NBT)-0.05BaTiO3 was grown by top-seeded solution growth method, which has rhombohedral symmetry with composition near morphotropic phase boundary. Full set of dielectric, piezoelectric, and elastic constants for [001]c poled domain-engineered single crystal was determined. Excellent electromechanical properties and low dielectric loss (d33 = 360 pC/N, d31 = −113 pC/N, d15 = 162 pC/N, k33 = 0.720, kt = 0.540, and tan δ = 1.1%) make it a good candidate to replace lead-based piezoelectric materials. The depolarization temperature (Td = 135 °C) is the highest among all NBT-based materials and its electromechanical coupling properties are very stable below Td. Extrinsic contributions to piezoelectric properties were investigated by Rayleigh analysis.

Orientation dependence of piezoelectric properties and mechanical quality factors of 0.27Pb(In1/2Nb1/2)O3-0.46Pb(Mg1/3Nb2/3)O3-0.27PbTiO3:Mn single crystals

The complete set of material constants of single domain rhombohedral phase 0.27Pb(In1/2Nb1/2)O3-0.46Pb(Mg1/3Nb2/3)O3-0.27PbTiO3:Mn single crystal has been determined. The orientation dependence of piezoelectric, dielectric, and electromechanical properties was calculated based on these single domain data. The maximum piezoelectric and electromechanical properties were found to exist near the [001]C pseudo-cubic direction. In addition, the piezoelectric properties of [001]C poled crystals with “4R” multi-domain configuration were experimentally measured and compared with the calculated values. Only a small difference (3%) was found between experimental and theoretical values, indicating the high piezoelectric properties in the “4R” state are mainly from intrinsic contributions. The mechanical quality factors Q33 are significantly improved by the Mn-doping for the “4R” domain engineered crystals but almost no change for the single domain “1R” state. On the other hand, Q15 of both single domain and multidoma...

A high quality lead-free (Li, Ta) modified (K, Na)NbO3 single crystal and its complete set of elastic, dielectric and piezoelectric coefficients with macroscopic 4mm symmetry

A high quality orthorhombic (K, Na, Li)(Nb, Ta)O3 single crystal with a large size of 9 × 9 × 11 mm3 was successfully grown using the top-seeded solution growth method. Its large size allowed us to perform comprehensive investigation on this crystal. A complete set of elastic, dielectric and piezoelectric coefficients was determined using combined resonance and ultrasonic methods. The longitudinal piezoelectric coefficient d33 and the transverse piezoelectric coefficient d31 of this lead-free piezoelectric single crystal are as high as 354 pC N−1 and −163 pC N−1, respectively, which are two times higher than those of KNN-TL ceramics and are comparable with those of PZT5. The electromechanical coupling factor k33 is as high as 82%, much higher than those of KNN-TL ceramics and PZT5. The coefficient d33,strain was found to be as high as 672 pm v−1 and the extrinsic contribution (~22%) was investigated by Rayleigh analysis. These high piezoelectric properties make this single crystal a promising candidate for replacing lead-based piezoelectric materials.

Ultrahigh-sensitive optical temperature sensing based on ferroelectric Pr3+-doped (K0.5Na0.5)NbO3

Optical temperature sensing based on the variation of the fluorescence intensity ratio of rare-earth materials has become appealing due to the multiple superiorities over the electrical temperature sensing. However, confined by the largest energy separation of two thermally linked levels of rare-earth ions, the highest sensitivity of such temperature sensing is essentially smaller than 2878/T2, as reported previously from diverse systems. In this work, we demonstrate that ultrahigh-sensitive temperature sensing can be achieved from Pr3+-doped (K0.5Na0.5)NbO3 based on the intensity ratio of the 1D2-3H4 emission to the 3P0-3H4 emission. The ratio can be increased as high as 18-fold when temperature rises from room temperature to 456 K, nicely fitting a thermally linked-levels-like equation and showing an ultrahigh sensitivity of 7997/T2. The striking change of the ratio is attributed to the interaction between the two emission levels and the intervalence charge transfer state. This work may have provided a ...

Complete set of material constants of single domain (K, Na)(Nb, Ta)O3 single crystal and their orientation dependence

A self-consistent complete set of dielectric, piezoelectric, and elastic constants for single domain Ta modified (K, Na)NbO3 (KNN) crystal was determined. This full set constant for single domain KNN-based crystals allowed the prediction of orientation dependence of the longitudinal dielectric, piezoelectric, elastic coefficients, and electromechanical coupling factors. The maximum piezoelectric and electromechanical properties were found to exist near [001] C . In addition, material constants of [001] C poled domain engineered single crystal with 4 mm symmetry were experimentally measured and compared with the calculated values. Based on this, extrinsic contribution to the piezoelectricity was estimated to be ∼20%.

Characterization of full set material constants of piezoelectric materials based on ultrasonic method and inverse impedance spectroscopy using only one sample.

The most difficult task in the characterization of complete set material properties for piezoelectric materials is self-consistency. Because there are many independent elastic, dielectric, and piezoelectric constants, several samples are needed to obtain the full set constants. Property variation from sample to sample often makes the obtained data set lack of self-consistency. Here, we present a method, based on pulse-echo ultrasound and inverse impedance spectroscopy, to precisely determine the full set physical properties of piezoelectric materials using only one small sample, which eliminated the sample to sample variation problem to guarantee self-consistency. The method has been applied to characterize the [001]C poled Mn modified 0.27Pb(In1/2Nb1/2)O3-0.46Pb(Mg1/3Nb2/3)O3-0.27PbTiO3 single crystal and the validity of the measured data is confirmed by a previously established method. For the inverse calculations using impedance spectrum, the stability of reconstructed results is analyzed by fluctuation analysis of input data. In contrast to conventional regression methods, our method here takes the full advantage of both ultrasonic and inverse impedance spectroscopy methods to extract all constants from only one small sample. The method provides a powerful tool for assisting novel piezoelectric materials of small size and for generating needed input data sets for device designs using finite element simulations.

Temperature dependence of dielectric and electromechanical properties of (K,Na)(Nb,Ta)O3 single crystal and corresponding domain structure evolution

Domain structures and their evolution with temperature in the [001] C oriented (K,Na)(Nb,Ta)O3 (KNNT) single crystal have been studied before and after poling by polarizing light microscopy. The results indicate that the KNNT crystal is difficult to be completely poled by the room temperature poling process. The domain structure is rather stable in the orthorhombic phase, but exhibits substantial changes near the phase transition temperatures TO-T and TC. Narrower stripe domains are formed during both the orthorhombic-tetragonal and tetragonal-cubic phase transition processes, no intermediate phases were found during the phase transitions. The temperature dependence of the dielectric and piezoelectric properties were measured, and the influence of domain structures on the dielectric and electromechanical properties were quantified.

A face-shear mode single crystal ultrasonic motor

We report a face-shear mode ultrasonic motor (USM) made of [011]c poled Zt ± 45° cut 0.24Pb(In1/2Nb1/2)O3-0.46Pb(Mg1/3Nb2/3)O3-0.30PbTiO3 single crystal, which takes advantage of the extremely large d36 = 2368 pC/N. This motor has a maximum no-load linear velocity of 182.5 mm/s and a maximum output force of 1.03 N under the drive of Vp = 50 V, f = 72 kHz. Compared with the k31 mode USM made of Pb(Zr,Ti)O3 (PZT), our USM has simpler structure, lower driving frequency, much higher electromechanical coupling factor, and twice power density. This USM can be used for low frequency operation as well as cryogenic actuation with a large torque.

Phase coexistence and domain configuration in Pb(Mg1/3Nb2/3)O3-0.34PbTiO3 single crystal revealed by synchrotron-based X-ray diffractive three-dimensional reciprocal space mapping and piezoresponse force microscopy

The crystalline phases and domain configuration in the morphotropic phase boundary composition Pb(Mg1/3Nb2/3)O3-0.34PbTiO3 (PMN-0.34PT) single crystal have been investigated by synchrotron-based X-ray 3D Reciprocal Space Mapping (3D-RSM) and Piezoresponse Force Microscopy. The coexistence of tetragonal (T) and monoclinic MC phases in this PMN-0.34PT single crystal is confirmed. The affiliation of each diffraction spot in the 3D-RSM was identified with the assistance of qualitative simulation. Most importantly, the twinning structure between different domains in such a mixed phase PMN-PT crystal is firmly clarified, and the spatial distribution of different twin domains is demonstrated. In addition, the lattice parameters of T and MC phases in PMN-0.34PT single crystal as well as the tilting angles of crystal lattices caused by the interfacial lattice mismatch are determined.