Phase-transition temperatures and piezoelectric properties of (Bi/sub 1/2/Li/sub 1/2/)TiO/sub 3/-(Bi/sub 1/2/K/sub 1/2/)TiO/sub 3/ lead-free ferroelectric ceramics

The phase-transition temperatures and piezoelectric properties of x(Bi_1/2Na_1/2)TiO_3-y(Bi_1/2Li_1/2)TiO_3-z(Bi_1/2K_1/2)TiO₃ [x + y + z = 1] (abbreviated as BNLKT100y-100z) ceramics were investigated. These ceramics were prepared using a conventional ceramic fabrication process. The phase-transition temperatures such as depolarization temperatures T_d, rhombohedral-tetragonal phase transition temperature T_R-T, and dielectric-maximum temperature T_m were determined using electrical measurements such as dielectric and piezoelectric properties. The X-ray powder diffraction patterns of BNLKT100y-100z show the morphotropic phase boundary (MPB) between rhombohedral and tetragonal at approximately z = 0.20, and the piezoelectric properties show the maximum at the MPB. The electromechanical coupling factor &33, piezoelectric constant d₃₃ and T_d of BNLKT4-20 and BNLKT8-20 were 0.603, 176 pC/N, and 171degC, and 0.590, 190 pC/N, and 115degC, respectively. In addition, the relationship between d₃₃ and T_d of tetragonal side and rhombohedral side for BNLKT4-100z and BNLKT8-100z were presented. Considering both high T_d and high d₃₃, the tetragonal side of BNLKT4-100z is thought to be the superior composition. The d₃₃ and T_d of BNLKT4-28 were 135 pC/N and 218degC, respectively. Moreover, this study revealed that the variation of Td is related to the variation of lattice distortion such as rhombohedrality 90-alpha and tetragonality c/a.     

Piezoelectric properties in (K0.5Bi0.5)TiO3-(Na0.5Bi0.5)TiO3-BaTiO3 lead-free ceramics.

Lead-free piezoelectric ceramics with compositions around the morphotropic phase boundary (MPB) x(Na0.5Bi0.5)TiO3-y(K0.5Bi0.5)TiO3-zBaTiO3 [x + y + z = 1; y:z = 2:1] were synthesized using conventional, solid-state processing. Dielectric maximum temperatures of 280 degrees C and 262 degrees C were found for tetragonal 0.79(Na0.5Bi0.5)TiO3-0.14(K0.5Bi0.5)TiO3-0.07BaTiO3 (BNBK79) and MPB composition 0.88(Na0.5Bi0.5)TiO3-0.08(K0.5Bi0.5)TiO3-0.04BaTiO3 (BNBK88), with depolarization temperatures of 224 degrees C and 162 degrees C, respectively. Piezoelectric coefficients d33 were found to be 135 pC/N and 170 pC/N for BNBK79 and BNBK88, and the piezoelectric d31 was determined to be -37 pC/N and -51 pC/N, demonstrating strong anisotropy. Coercive field values were found to be 37 kV/cm and 29 kV/cm for BNBK79 and BNBK88, respectively. The remanent polarization of BNBK88 (approximately 40 microC/cm2) was larger than that of BNBK79 (approximately 29 microC/cm2). The piezoelectric, electromechanical, and high-field strain behaviors also were studied as a function of temperature and discussed.     

铌镁酸铋-钛酸铅压电陶瓷准同型相界附近的性能和相变温度研究

利用传统固相烧结法制备了Bi(Mg_2/3Nb_1/3)O₃-PbTiO₃(BMN-PT)压电陶瓷, 分析了不同PbTiO₃含量对BMN-PT压电陶瓷的晶体结构、介电、压电及铁电性能的影响. XRD结果表明: 合成的BMN-PT陶瓷具有纯钙钛矿结构, 并且在PbTiO₃含量为x=0.60时, 其组分的XRD图谱在衍射角2θ=45°出现明显的分峰, 说明该组分相结构中存在三方和四方相的共存. 压电铁电性能显示, BMN-0.60PT有最大的压电常数d₃₃(~170pC/N)和平面机电耦合系数k_p(0.35), 最小的矫顽场E_c(29.4 kV/cm)及最大的剩余极化P_r(31.4 μC/cm²). 确定了BMN-PT压电陶瓷的准同型相界(MPB)为PbTiO₃含量x=0.60的组分. 介电系数温谱表明介电系数峰值温度(Tm)随着PbTiO₃含量的增大而升高, MPB组分的Tm约为276℃.     

Dielectric and ferroelectric properties of Bi(Zn1/2Ti1/2)O3-PbTiO3-PbZrO3 ternary ceramics

Ceramics of a new ternary solid solution system, xBi(Zn(1/2)Ti(1/2))O(3-yPbTiO(3)z)PbZrO(3) (xBZT-yPT-zPZ), with compositions along the solubility limit curve are prepared by solid-state reaction and sintering technique. Two morphotropic phase boundaries (MPBs) separating the orthorhombic and tetragonal (MPB(O-T)) phases and the tetragonal and rhombohedral (MPB(T-R)) phases, respectively, are observed with increasing z (0.10 ≤ x ≤ 0.21; 0 ≤ y ≤ 0.49). It is found that the transition from the ferroelectric to paraelectric phase becomes more diffuse with the addition of BZT into the PZT solid solution. Enhanced dielectric and ferroelectric properties appear at MPB(R-T), which exists over a wide composition region (0.45 ≤ z ≤ 0.6), as revealed by X-ray diffraction and dielectric measurements. The dielectric constant reaches a maximum value (ε' = 1250) on the tetragonal majority side of the MPB. The highest remnant polarization (P(r) = 34.2 μC/cm(2)) is found in the composition at the center of the MPB, where the rhombohedral and tetragonal phases coexist in almost equal quantities.     

Piezoelectric properties in (K0.5Bi0.5)TiO 3-(Na0.5Bi0.5)TiO3-BaTiO 3 lead-free ceramics

Lead-free piezoelectric ceramics with compositions around the morphotropic phase boundary (MPB) x(Na_0.5Bi_0.5)TiO _3-y(K_0.5Bi_0.5)TiO₃-zBaTiO ₃ [x + y + z = 1; y:z = 2:1] were synthesized using conventional, solid-state processing. Dielectric maximum temperatures of 280degC and 262degC were found for tetragonal 0.79(Na_0.5Bi_0.5)TiO₃-0.14(K_0.5 Bi_0.5)TiO₃-0.07BaTiO$ d3 (BNBK79) and MPB composition 0.88(Na_0.5Bi_0.5)TiO₃-0.08(K _0.5Bi_0.5)TiO₃-0.04BaTiO$ d3 (BNBK88), with depolarization temperatures of 224degC and 162degC, respectively. Piezoelectric coefficients d₃₃ were found to be 135 pC/N and 170 pC/N for BNBK79 and BNBK88, and the piezoelectric d₃₁ was determined to be -37 pC/N and -51 pC/N, demonstrating strong anisotropy. Coercive field values were found to be 37 kV/cm and 29 kV/cm for BNBK79 and BNBK88, respectively. The remanent polarization of BNBK88 (~40 muC/cm²) was larger than that of BNBK79 (~29 muC/cm²). The piezoelectric, electromechanical, and high-field strain behaviors also were studied as a function of temperature and discussed     

Depolarization temperature and piezoelectric properties of Na1/2Bi1/2TiO3-Na1/2Bi1/2(Zn1/3Nb2/3)O3 ceramics by two-stage calcination method

A new group of NBT-based lead-free piezoelectric ceramics, Na_1/2Bi_1/2TiO₃-Na_1/2Bi_1/2(Zn_1/3Nb_2/3)O₃, was synthesized using the two-stage calcination method and depolarization temperatures and piezoelectric properties were also investigated. The XRD analysis showed that the ceramics system had a morphotropic phase boundary (MPB) between the rhombohedral and the tetragonal structure. The highest piezoelectric properties of d ₃₃ = 97 pC/N and k _t = 0·46 were obtained near MPB compositions. Furthermore, the depolarization temperatures near MPB compositions were slightly decreased and the lowest T _d was maintained at 210°C.     

Fabrication and evaluation of a single-element Bi(0.5)Na(0.5)TiO(3)-based ultrasonic transducer

This paper discusses the fabrication and characterization of a single-element ultrasonic transducer with a lead-free piezoelectric active element. A piezoelectric ceramic with composition of 0.88Bi(0.5)Na(0.5)TiO(3)-0.08Bi(0.5)K(0.5)TiO(3)- 0.04Bi(0.5)Li(0.5)TiO(3) was chosen as the active element of the transducer. This composition exhibited a thickness coupling coefficient (kt) of 0.45, a dielectric constant of 440 (at 1 kHz), and a longitudinal piezoelectric coefficient (d(33)) of 84 pC?N(-1). To make the transducer, the ceramic was sandwiched between an epoxy-tungsten backing layer and a silver epoxy matching layer. An epoxy lens was also incorporated into the transducer?s design to focus the ultrasound beam. The focused transducer with a center frequency of about 23 MHz demonstrated a -6-dB bandwidth of 55% and an insertion loss of -32 dB; the -20-dB pulsed length was measured to be 150 ns. A phantom made of copper wires (30 μm in diameter) was utilized to investigate the imaging capability of the transducer. The results indicated that the fabricated transducer, with a lateral resolution of 260 μm and a relatively high depolarization temperature, could be considered as a candidate for replacement of lead-based ultrasonic transducers.     

Field-induced phase transition and relaxor character in submicrometer-structured lead-free (Bi0.5Na0.5)0.94Ba0.06TiO3 piezoceramics at the morphotropic phase boundary

Submicrometer-structured (Bi(0.5)Na(0.5))(0.94)Ba(0.06)TiO(3) ceramics ((G) < 720 nm) from nanopowders were studied. The real part of the optimum room temperature set of piezoelectric coefficients obtained from resonances of the BNBT6 dense ceramic disks and shear plates [d(31) = (-37 + 1.33i) pC·N(-1), d(15) = (158.3 - 8.31i) pC·N(-1), k(t) = 40.4%, k(p) = 26.8%, and k(15) = 40.2%] and d(33) (148 pC·N(-1)) can be compared with the reported properties for coarse-grained ceramics. Shear resonance of thickness-poled plates is observed at T = 140°C. Permittivity versus temperature curves of poled samples show relaxor character up to T(i) = 230°C on heating and T(i) = 210°C on cooling of the depoled samples. The phase transition from the room-temperature ferroelectric (FE) to a low-temperature non-polar at zero field (LTNPZF) phase can be observed as a sharp jump in ε(δ)(33)'(T) curves or, as the degree of poling decreases, as a soft change of slope of the curves at T(FE-LTNPZF) = T(d) = 100°C. This dielectric anomaly is not observed on cooling of depoled samples, because the FE phase is field-induced. The observed macroscopic piezoelectric activity above T(d) is a consequence of the coexistence of nanoregions of the FE phase in the interval between T(FE-LTNPZF) and T(i).     

Dielectric and piezoelectric properties of (0.97-x) Bi1/2Na1/2TiO3-xBi1/2K1/2TiO3-0.03NaNbO3 ceramics

Ceramics of the series (0.97-x)Bi_1/2Na_1/2TiO₃-xBi_1/2K_1/2TiO₃-0.03NaNbO₃ (x = 0, 0.02, 0.06, 0.10, 0.16, 0.20, 0.30) were prepared by the conventional mixed oxide method. Influence of Bi_1/2K_1/2TiO₃ content on the crystal structure, microstructure, dielectric and piezoelectric properties were studied. All compositions showed single perovskite phase and the morphotropic phase boundary (MPB) between rhombohedral and tetragonal phase existed at the point of x = 0.16. Temperature dependences of permittivity and dissipation factor of unpoled samples revealed that permittivity increased with Bi_1/2K_1/2TiO₃ content and it reached maximum value near the MPB. At the same time, the peak value of dissipation factor increased with the addition of Bi_1/2K_1/2TiO₃. All the samples experienced two phase transitions: from ferroelectric to antiferroelectric at the first transition temperature (T_d) and from antiferroelectric to paraelectric at the temperature (T_m) corresponding to maximum value of permittivity. The phase transition from ferroelectric to antiferroelectric had relaxor characteristic and T_d shifted to lower temperature while increasing Bi_1/2K_1/2TiO₃ content. The best piezoelectric properties were obtained in 0.81Bi_1/2Na_1/2TiO₃-0.16Bi_1/2K_1/2TiO₃-0.03NaNbO₃ ceramic with a piezoelectric constant (d₃₃) of 146pC/N, planar electromechanical coupling factor (k_p) of 30.3% and thickness electromechanical coupling factor (k_t) of 53.2%. Abnormal piezoelectric properties were observed in the sample (x = 0.20), which was attributed to the co-existence of ferroelectric and antiferroelectric phases in it.     

Tem analyses of the local crystal and domain structures in (Na(1-x)K(x))0.5Bi(0.5)TiO3 perovskite ceramics

The local crystal and domain structures of the ((Na(1-x)K(x))(0.5)Bi(0.5)TiO(3) (NBT-KBT) solid solutions were studied because of their influence on the enhanced electromechanical properties of ceramics. Based on X-ray diffraction, the morphotropic phase boundary (MPB) was determined for the composition x = 0.20, in which the rhombohedral and the tetragonal structures were observed to coexist. However, detailed domain-structure analyses using transmission electron microscopy (TEM), performed on the NBT, KBT, and five NBT-KBT solid-solution compositions, revealed some structural changes at/near the MPB. In the samples on the tetragonal side of the MPB, the grains showed a lamellar domain structure with 90° orientations of the individual domains, separated by straight domain boundaries, i.e., (011)/(101) twin planes. The rhombohedral samples on the other side of the MPB showed a typical square-net pattern with needle-like or lamellar ~71°/109° rhombohedral domains with (001) and/or (110) twin planes separating the individual domains. The domain structure at the MPB showed well-defined lamellar domains. Based on the occurrence of the superstructure reflections in the SAED patterns of various crystallographic zones, on the characteristic splitting of the reflections, and on the domain morphology observations, the crystal structure in/near the boundary region was determined to be a tetragonal structure with an in-phase oxygen octahedral tilt system (probably a(0)a(0)c(+)). It is suggested that the tetragonal polar order is partly induced from the rhombohedral structure at the MPB as a result of mechanical loading during TEM sample preparation.     

Temperature independent shear piezoelectric response in relaxor-PbTiO(3) based crystals

The temperature dependence of the shear piezoelectric responses in relaxor-PbTiO(3) based perovskite crystals with rhombohedral, orthorhombic, and tetragonal phases were investigated. Based on thermodynamic analysis, high shear piezoelectric coefficients (d(24)) and good thermal stability were predicted in orthorhombic crystals, owing to the "vertical" orthorhombic-rhombohedral phase boundary. By resonance measurements, shear piezoelectric coefficient d(24) was found to be on the order of ～2100 pC∕N at room temperature, maintaining same value over the temperature range of -50-100 °C. In contrast, the shear piezoelectric coefficients d(15), with values of 3300, 3600, and 2000 pC∕N at room temperature for rhombohedral, orthorhombic, and tetragonal crystals, respectively, exhibited strong temperature dependent behavior due to their respective ferroelectric-ferroelectric phase transitions.     

Dielectric and piezoelectric properties of perovskite materials at cryogenic temperatures

Dielectric and piezoelectric properties of perovskite materials including La modified Pb(Zr, Ti)O3 (PZT's), (Ba, Sr)TiO3 (BST) polycrystalline ceramics and Pb(Zn1/3 Nb2/3)O3-PbTiO3 (PZN-PT) single crystals were investigated for capacitor and actuator applications at cryogenic temperatures. PZTs were compositionally engineered to have decreased Curie temperatures (Tc) by La and Sn doping in order to compensate for the loss of extrinsic contributions to piezoelectricity at cryogenic temperatures. Enhanced extrinsic contributions resulted in piezoelectric coefficients (d33) as high as 250 pC/N at 30 K, superior to that of conventional DOD Type PZT's (d33~100 pC/N). This property enhancement was associated with retuning to the MPB at cryogenic temperatures. 5/95 BST with a dielectric maximum at 57 K was investigated to obtain high electrostrictive properties or E-field induced piezoelectricity. Coupling coefficients (k31) 25% comparable to those of the cryogenic PLZT piezoelectrics were observed at d.c. bias of 1.5 kV/cm and 50 K. Though significantly lower than the room temperature values, PZN-PT rhombohedral single crystals exhibited d33> 500 pC/N at 30 K.     

三元陶瓷Pb(In1/2Nb1/2)O3-Pb(Ni1/3Nb2/3)O3-PbTiO3准同型相界附近组分的介电、铁电和压电性能

铅基复合钙钛矿铁电材料广泛应用于机电传感器、致动器和换能器。二元铁电固溶体Pb(Ni_1/3Nb_2/3)O₃- PbTiO₃(PNN-PT)由于其在准同型相界(MPB)区域具有优异的压电、介电性能而备受关注。然而较大的介电损耗和较低的居里温度限制了其在高温高功率器件方面的应用。本研究通过引入Pb(In_1/2Nb_1/2)O₃ (PIN)作为第三组元改善PNN-PT的电学性能, 提高其居里温度; 通过两步法合成了MPB区域的三元铁电陶瓷Pb(In_1/2Nb_1/2)O₃- Pb(Ni_1/3Nb_2/3)O₃-PbTiO₃ (PIN-PNN-PT), 研究了其结构、介电、铁电和压电性能。制备的所有组分陶瓷具有纯的钙钛矿结构。随着PT含量的增加, 陶瓷结构从三方相转变为四方相。通过XRD分析得到了室温下PIN-PNN-PT体系的MPB相图。体系的居里温度由于PIN的加入得到了很大的提高, 更重要的是PIN的引入降低了PNN-PT体系的介电损耗和电导。MPB处的组分展现出了优异的电学性能, 室温下, 性能最优组分为0.30PIN-0.33PNN-0.37PT: d₃₃=417 pC/N, T_C=200 ℃, ε′= 3206, tanδ=0.033, P_r=33.5 μC/cm², E_C=14.1 kV/cm。引入PNN-PT的PIN第三组元使得体系的居里温度和压电性得到提高的同时降低了的介电损耗和电导率, 因此, PIN-PNN-PT三元铁电陶瓷在高温高功率换能器等方面具备一定的应用潜力。     

Synthesis and electrical properties of (Bi(1/2)Na(1/2))TiO3 (BNT) ferroelectric thin films by liquid sprayed mist chemical vapor deposition technique

This study aims to synthesize lead-free ferroelectric material, (Bi(1/2)Na(1/2))TiO3 using the Liquid Sprayed Mist Chemical Vapor Deposition (LSMCVD) technique. The mist of precursor solution was vaporized and deposited on two different substrates of Si(100) and (111)Pt/TiO2/SiO2/Si(100) in an oxygen atmosphere. The deposition temperature and time were varied in the range of 400-600 degrees C and 30-90 min. (Bi(1/2)Na(1/2))TiO3 thin film had preferred orientations of (110). The thickness of the thin film deposited was 35-162 nm. The remnant polarization (2Pr) and the dielectric constant were 4.6-16.8 microC/cm2, 325-350, respectively.     

Pb(Mn1/3Sb2/3)0.05Zr0.47Ti0.48O3压电陶瓷的温度稳定性研究

探讨了硬性添加物MnO2、软性添加物Nb2O5和两性添加物Cr2O3对锑锰锆钛酸铅Pb(Mn1/3Sb2/3)0.05Zr0.47Ti0.48O3(简称PMSZT5)压电陶瓷的相组成及温度稳定性的影响.研究结果发现:各掺杂组成在900℃的煅烧温度下,都可以得到钙钛矿结构.随着各掺杂离子的增大,四方相含量减少,准同型相界向三方相移动.综合考虑离子掺杂对PMSZT5压电陶瓷的机电性能及温度稳定性的研究结果表明:锰过量较其它铌和铬掺杂的温度稳定性更好,机电性能最佳的PMSZT5+0.1wt%MnO2的组成,ε33T/ε0=1560,d33=350pC/N,Kp=0.63,25~80℃的fr、K31和d31平均温度系数分别为72×10-6/℃、0.027%/℃和0.100%/℃.     

Elastic, piezoelectric, and dielectric properties of 0.955Pb(Zn(1/3)Nb(2/3))O(3)-0.45PbTiO(3 ) single crystal with designed multidomains

The elastic, piezoelectric, and dielectric properties of a 0.955Pb(Zn(1/3)Nb(2/3))O(3)-0.045PbTiO(3 ) (PZN-4.5%PT) multi-domain single crystal, poled along [001] of the original cubic direction, have been determined experimentally using combined resonance and ultrasonic methods. At room temperature, the PZN-4.5%PT single crystal has rhombohedral symmetry. After being poled along [001], four degenerate states still remain. Statistically, such a domain-engineered crystal may be treated as having an average tetragonal symmetry, and its material constants were determined based on 4 mm symmetry. It was confirmed that the electromechanical coupling coefficient k(33) for the domain-engineered samples is >90%, and the piezoelectric constant d(33) is >2000 pC/N. A soft shear mode with a velocity of 700 m/s was found in the [110] direction. From the measured experimental data, the orientational dependence of phase velocities and electromechanical coupling coefficients was calculated. The results showed that the transverse and longitudinal coupling coefficients, k(31) and k(33), reach their maximum along [110] and [001], respectively.     

Complete set of material properties of [011](c) poled 0.24Pb(In(1/2)Nb(1/2))O(3)-0.46Pb(Mg(1/3)Nb(2/3))O(3)-0.30PbTiO(3) single crystal

A complete set of elastic, piezoelectric, and dielectric constants of [011](c) poled multidomain 0.24Pb(In(1/2)Nb(1/2))O(3)-0.46Pb(Mg(1/3)Nb(2/3))O(3)-0.30PbTiO(3) ternary single crystal has been determined using resonance and ultrasonic methods and the temperature dependence of the dielectric permittivity has been measured at 3 different frequencies. The experimental results revealed that this [011](c) poled ternary single crystal has very large transverse piezoelectric coefficient d(32) = -1693 pC/N, transverse dielectric constant ε(11)/ε(0) ~ 7400 and a high electromechanical coupling factor k(32) ~ 90%. In addition, its coercive field is 2 times of that of the corresponding binary 0.7Pb(Mg(1/3)Nb(2/3))O(3)-0.30PbTiO(3) single system with much better temperature stability. Therefore, the crystal is an excellent candidate for transverse mode electromechanical devices.     

非化学计量比对(K0.465Na0.465Li0.07)(Nb0.95Sb0.05)O3无铅压电陶瓷结构及性能的影响

通过传统固相合成工艺制备了(K0.465+xNa0.465+yLi0.07)(Nb0.95-zSb0.05)O3(x,y,z=-0.01～0.02)无铅压电陶瓷,研究了非化学计量比对陶瓷结构及压电性能的影响。结果表明符合化学计量比的陶瓷具有四方钙钛矿结构;在实验范围内,K和Nb的过量或少量均不会改变体系的相结构,而Na过量将会导致体系正交-四方相变温度升高到室温以上,并且正交-四方相变温度随y的增加而升高;过量添加约0.5%(摩尔分数)的K或Na便能补偿在高温烧结时的碱金属元素的挥发损失,进而提高陶瓷的压电性能;该体系陶瓷的组分在较大范围内变化时(如当y=z=0时,x=0～0.02;当x=z=0时,y=0～0.01;以及当x=y=0时,z=-0.01～0.005),仍然能保持d33>200pC/N和kP>40%这样较好的性能。上述结果不仅有利于在研究中材料制备工艺的重复,而且有利于当材料在器件应用时所面临的规模化生产。     

Dielectric and piezoelectric properties in the lead-free system Na0.5K0.5NbO3-BiScO3-LiTaO3

Phase relations, dielectric and piezoelectric properties are reported for the ternary system 98%[(1 - x) (Na(0.5)K(0.5)NbO(3))-x(LiTaO(3))]-2%[BiScO(3)] for compositions x ≤ 10 mol% LiTaO(3). The phase content at room-temperature changed from mixed phase, monoclinic + tetragonal, for unmodified 98%(Na(0.5)K(0.5)NbO(3))-2%(BiScO(3)), to tetragonal phase for compositions >2 mol% LiTaO(3). Curie peaks at 360 to 370°C were observed for all compositions, but peaks became diffuse at x ≥ 3 mol%, and two dielectric peaks, at 370 and 470°C, were observed for 5 mol% LiTaO(3). Phase segregation, and finite size affects associated with the core-shell structure, account for the occurrence of two dielectric peaks in 5 mol% LiTaO(3), and diffuse dielectric behavior. The value of d(33) piezoelectric charge coefficient increased from ~160 pC/N for 0 mol% LiTaO(3) to 205 to 214 pC/N for 1 to 2 mol% LiTaO3 solid solutions, before falling sharply at 3 mol% LiTaO(3). TEM-EDX analysis revealed core-shell grain structures with segregation of Bi, Sc, and Ta in the outer ~100-nm shell of the 5 mol% LT sample.     

Enhanced ferro- and piezoelectric properties in (100)-textured Nb-doped Pb(ZrxTi1 − x)O3 films with compositions at morphotropic phase boundary

To develop high-performance piezoelectric films on conventional Pt(111)/Ti/SiO₂/Si(100) substrates, sol-gel-derived highly [100]-textured Nb-doped Pb(Zr_xTi_1 − x)O₃ (PNZT) thin films with different Zr/Ti ratios ranging from 20/80 to 80/20 were prepared and characterized. The phase structure, ferroelectric and piezoelectric properties of the PZNT films were investigated as a function of Zr/Ti ratios, and it was confirmed that there was distinct phase transition of the PNZT system from tetragonal to rhombohedral when the Zr/Ti ratio varied across the morphotropic phase boundary (MPB). The Nb-doped PZT films showed enhanced remanent polarization but reduced coercive field, whose best values reached 75 μC/cm² and 82 kV/cm, respectively at the composition close to MPB. In addition, the [100]-textured PNZT film at MPB also shows a high piezoelectric coefficient up to 161 pm/V. All these properties are superior to those for undoped PZT films.