Preparation of (001)-oriented Pb(Zr,Ti)O3 thin films and their piezoelectric applications

Preparation of (001)-oriented Pb(Zr,Ti)O(3) (PZT) thin films and their applications to a sensor and actuators were investigated. These thin films, which have a composition close to the morphotropic phase boundary, were epitaxially grown on (100)MgO single-crystal substrates by RF magnetron sputtering. These (001)-oriented PZT thin films could be obtained on various kinds of substrates, such as glass and Si, by introducing (100)-oriented MgO buffer layers. In addition, the (001) oriented PZT thin films could be obtained on Si substrates without buffer layers by optimizing the sputtering conditions. All of these thin films showed excellent piezoelectric properties without the need for poling treatment. The PZT thin films on the MgO substrates had a high piezoelectric coefficient, d(31), of -100 pm/V, and an extremely low relative dielectric constant, epsilon(r), of 240. The PZT thin films on Si substrate had a very high d(31) of -150 pm/V and an epsilon(r) = 700. These PZT thin films were applied to an angular rate sensor with a tuning fork in a car navigation system, to a dual-stage actuator for positioning the magnetic head of a high-density hard disk drive, and to an actuator for an inkjet printer head for industrial on-demand printers.     

Preparation of (001)-oriented Pb(Zr,Ti)O/sub 3/ thin films and their piezoelectric applications

Preparation of (001)-oriented Pb(Zr,Ti)O₃ (PZT) thin films and their applications to a sensor and actuators were investigated. These thin films, which have a composition close to the morphotropic phase boundary, were epitaxially grown on (100)MgO single-crystal substrates by RF magnetron sputtering. These (001)-oriented PZT thin films could be obtained on various kinds of substrates, such as glass and Si, by introducing (100)-oriented MgO buffer layers. In addition, the (001)-oriented PZT thin films could be obtained on Si substrates without buffer layers by optimizing the sputtering conditions. All of these thin films showed excellent piezoelectric properties without the need for poling treatment. The PZT thin films on the MgO substrates had a high piezoelectric coefficient, d₃₁, of -100 pm/V, and an extremely low relative dielectric constant, epsiv_r, of 240. The PZT thin films on Si substrate had a very high d₃₁ of -150 pm/V and an epsiv_r = 700. These PZT thin films were applied to an angular rate sensor with a tuning fork in a car navigation system, to a dual-stage actuator for positioning the magnetic head of a high-density hard disk drive, and to an actuator for an inkjet printer head for industrial on-demand printers.     

Highly polarized single-c-domain single-crystal Pb(Mn,Nb)O(3)-PZT thin films

In-plane unstrained single-c-domain/single-crystal thin films of PZT-based ternary ferroelectric perovskite, ξPb(Mn,Nb)O3-(1 - ξ)PZT, were grown on SrRuO(3)/Pt/MgO substrates using magnetron sputtering followed by quenching. The sputtered unstrained thin films exhibit unique ferroelectric properties: high coercive field, Ec > 180 kV/cm, large remanent polarization, P(r) = 100 μC/cm(2), small relative dielectric constants, ε* = 100 to 150, high Curie temperature, Tc = ~600 °C, and bulk-like large transverse piezoelectric constants, e31,f = -12.0 C/m(2) for PZT(48/52) at ξ = 0.06. The unstrained thin films are an ideal structure to extract the bulk ferroelectric properties. Their micro-structures and ferroelectric properties are discussed in relation to the potential applications for piezoelectric MEMS.     

Mg/sub x/Zn/sub 1-x/O: a new piezoelectric material

Piezoelectric ZnO thin films have been successfully used for multilayer surface acoustic wave (SAW) and bulk acoustic wave (BAW) devices. Magnesium zinc oxide (Mg/sub x/Zn/sub 1-x/O) is a new piezoelectric material, which is formed by alloying ZnO and MgO. Mg/sub x/Zn/sub 1-x/O allows for flexibility in thin film SAW device design, as its piezoelectric properties can be tailored by controlling the Mg composition, as well as by using Mg/sub x/Zn/sub 1-x/O/ZnO multilayer structures. We report the metal-organic chemical vapor deposition (MOCVD) growth, structural characterization and SAW evaluation of piezoelectric Mg/sub x/Zn/sub 1-x/O (x<0.35) thin films grown on (011~2) r-plane sapphire substrates. The primary axis of symmetry, the c-axis, lies on the Mg/sub x/Zn/sub 1-x/O growth plane, resulting in the in-plane anisotropy of piezoelectric properties. SAW test devices for Rayleigh and Love wave modes, propagating parallel and perpendicular to the c-axis, were designed and fabricated. Their SAW properties, including velocity dispersion and piezoelectric coupling, were characterized. It has been found that the acoustic velocity increases, whereas the piezoelectric coupling decreases with increasing Mg composition in piezoelectric Mg/sub x/Zn/sub 1-x/O films.     

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.     

Fabrication and optical properties of Pb(Mg(1/3)Nb(2/3))O(3)-PbTiO(3) thin films on Si substrates using the PLD method.

Epitaxial 0.67Pb(Mg(1/3)Nb(2/3))O(3)-PbTiO(3)-0.33PbTiO(3) (PMN-PT) thin films with electro-optic effects were fabricated on (PMN-PT) thin films with electro-optic effects were fabricated on (La0(0.5)Sr0(0.5))CoO(3) (LSCO)/CeO(2)/YSZ-buffered Si(001) substrates using double-pulse excitation pulsed laser deposition (PLD) method with a mask placed between the target and the substrate. Epitaxial growth of PMN-PT thin films was undertaken using the two-step growth method of PMN-PT film. The PMN-PT seed layer was deposited at 500 degrees C on the LSCO/CeO(2)/YSZ/Si, which temperature was the same as that used for LSCO deposition. The PMN-PT thin films were deposited on the PMN-PT seed layer at 600 degrees C, which enables growth of high-crystallinity PMN-PT films with smooth surfaces. We obtained optimum fabrication conditions of PMNPT film with micrometer-order thickness. Resultant films showed high crystallinity with full width at half maximum (FWHM) = 0.73 deg and 1.6 mum thickness. Electro-optic properties and the refractive index value were measured at 633 nm wavelength using the prism coupling method. The obtained refractive index was 2.59. The electro-optic coefficients r(13) and r(33) were determined by applying the electrical field between a semitransparent, thin top electrode of Pt and a bottom LSCO electrode. The electro-optic coefficient was r(13) = 17 pm/V at transverse electric field (TE) mode and r(33) = 55 pm/V at transverse magnetic field (TM) mode.     

力电多场鼓包法测定PZT铁电薄膜的横向压电系数

为表征Pb(Zr_(0.52)Ti_(0.48))O_3(PZT)薄膜的横向压电性能,以纯力场鼓包测试模型和铁电薄膜材料压电方程为基础,推导了PZT铁电薄膜的力电耦合鼓包本构模型。采用溶胶-凝胶法制备了PZT铁电薄膜,并通过化学腐蚀法获得PZT薄膜鼓包样品。在外加电压为0~14V的条件下进行鼓包测试。结果表明,在纯力场作用下,PZT薄膜的弹性模量和残余应力分别为91.9GPa和36.2MPa;随着电压从2V变化到14V,PZT薄膜的横向压电系数d31从-28.9pm/V变化到-45.8pm/V。本工作所发展的力电耦合鼓包测试技术及力电耦合鼓包本构模型为评价铁电薄膜材料的横向压电性能提供了一种有效的分析方法。     

Phase-transition temperatures and piezoelectric properties of (Bi1/2Na1/2)TiO3-(Bi1/2Li1/2)TiO3-(Bi1/2K1/2)TiO3 lead-free ferroelectric ceramics.

The phase-transition temperatures and piezoelectric properties of x(Bi(1/2)Na(1/2))TiO3-y(Bi(1/2)Li(1/2))TiO3-z(Bi(1/2)K(1/2))TiO3 [x + y + z = 1] (abbreviated as BNLKT100(y)-100(z)) ceramics were investigated. These ceramics were prepared using a conventional ceramic fabrication process. The phase-transition temperatures such as depolarization temperatures T(d), rhombohedraltetragonal 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 BNLKT100(y)-100(z)) 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 k(33), piezoelectric constant d(33) and T(d) of BNLKT4-20 and BNLKT8-20 were 0.603, 176 pC/N, and 171 degrees C, and 0.590, 190 pC/N, and 115 degrees C, respectively. In addition, the relationship between d33 and Td of tetragonal side and rhombohedral side for BNLKT4-100z and BNLKT8-100z were presented. Considering both high Td and high d(33), the tetragonal side of BNLKT4-100z is thought to be the superior composition. The d(33) and T(d) of BNLKT4-28 were 135 pC/N and 218 degrees C, respectively. Moreover, this study revealed that the variation of T(d) is related to the variation of lattice distortion such as rhombohedrality 90-alpha and tetragonality c/a.     

Terahertz dielectric response of ferroelectric Ba(x)Sr(1-x)TiO3 thin films

Terahertz time-domain spectroscopy has been used to investigate the dielectric and optical properties of ferroelectric Ba(x)Sr(1-x)TiO(3) thin films for nominal x-values of 0.4, 0.6, and 0.8 in the frequency range of 0.3 to 2.5 THz. The ferroelectric thin films were deposited at approximately 700 nm thickness on [001] MgO substrate by pulsed laser deposition. The measured complex dielectric and optical constants were compared with the Cole-Cole relaxation model. The results show that the Cole-Cole relaxation model fits well with the data throughout the frequency range and the dielectric relaxation behavior of ferroelectric Ba(x)Sr(1-x)TiO(3) thin films varies with the films compositions. Among the compositions of Ba(x)Sr(1-x)TiO(3) films with different Ba/Sr ratios, Ba(0.6)Sr(0.4)TiO(3) has the highest dielectric constants and the shortest dielectric relaxation time.     

Sintering and piezoelectric properties of KNN ceramics doped with KZT

This paper investigates the effect of K(1.94)Zn(1.06)Ta(5.19)O(15) (KZT) addition on the sintering behavior and piezoelectric properties in lead free piezoelectric ceramics of (K(0.5)Na(0.5))NbO(3) (KNN). The apparent density of sintered KNN ceramics was increased with KZT addition, and a relative density of above 96.3% was obtained with the doping of over 0.5 mol% KZT. The maximum dielectric and piezoelectric properties of epsilon(T)(3)/epsilon(0) = 590, d(33) = 126 pC/N, k(p) = 0.42, and P(r) = 18 microC/cm(2) were obtained from 0.5 mol% KZT-doped KNN ceramics. A small amount of KZT (about 0.5 mol%) was effective for improving the sintering behavior and piezoelectric properties, but KZT addition exceeding 1.0 mol% was effective only for densification. A small amount of KZT was effective for densification of KNN ceramics by promoting K(5.75)Nb(10.8)O(30) liquid phase formation. However, even though KNN with 1.0 to approximately -2.0 mol% KZT had a relative density of >98.5%, the piezoelectric properties were inferior to those of 0.5 mol% KZT-doped KNN, presumably due to the smaller grain size and excess liquid phase of the KNN ceramics doped with higher amounts of KZT. It is believed that a small amount of KZT could be one of the suitable sintering aids to obtain highly dense KNN based piezoelectric.     

Temperature dependence of oriented growth of Pb[Yb(1/2)Nb(1/2)]O(3)-PbTiO(3) thin films deposited on LNO/Si substrates

(1-x)Pb[Yb(1/2)Nb(1/2)]O(3)-xPbTiO(3) (PYbN-PT, x=0.5)(001) oriented thin films were deposited onto LaNiO3 (LNO)/Si(001) substrates by sol-gel processing. The crystallographic texture of the films was controlled by the annealing temperature and heating rate. Highly (001) oriented LNO thin films were prepared by a simple metal organic decomposition technique, and the samples were annealed at 700 °C and 750 °C using a rapid thermal annealing process and furnace, respectively. X-ray diffraction analysis revealed that the films of PYbN-PT were highly (001) oriented along LNO/Si substrates. The degree of PYbN-PT orientation is dependent on the heating rate and annealing temperature. Annealing heating rate of 10 °C/s and high annealing temperature near 750 °C produce the greatest degree of (001) orientation, which gives rise to improved dielectric properties.     

NbO3-LiNbO3无铅压电陶瓷的烧结特性和压电性能研究

采用传统陶瓷烧结工艺制备了（1-x）（K0．5Na0．5）NbO3-xLiNbO3无铅压电陶瓷，研究了陶瓷的结构、烧结特性及电性能特征．制备的（K0．5Na0．5）NbO3-LiNbO3陶瓷为单一的钙钦矿结构，室温下其相结构随LiNbO3含量增加逐渐由正交相向四方相转变，显微结构也由于LiNbO3含量的不同而表现出很大差异．与（K0．5Na0．5）NbO3陶瓷相比，（K0．5Na0．5）NbO3-LiNbO3陶瓷的烧结温度降低，烧结特性得到改善．（K0．5Na0．5）NbO3-LiNbO3陶瓷表现出优越的压电性能，其中0．94（K0．5Na0．5）NbO3—0．06LiNbO3（x=0．06）陶瓷的压电常数d33达到205pC／N，机电耦合系数kp为40．3％，kt达到49．8％．     

Optical waveguiding in epitaxial PbTiO(3) thin films

Epitaxial lead titanate (PbTiO(3)) thin films on SrTiO(3) (100) substrate were grown in situ by radio-frequency sputtering for optical waveguiding applications. The crystalline quality of the PbTiO(3) films deposited at 550 degrees C has been investigated through x-ray diffraction analysis. It indicates that thin films are completely c-axis oriented (rocking curve FWHM of 0.2 degrees for the 001 reflection). The transmission spectrum method has been used to measure the dispersion of the refractive index. At 632.8 nm, the PbTiO(3) film with an (001) orientation exhibits a refractive index of 2.61, which represents 98% of the bulk material. The prism-coupling technique has been also employed to determine the optical attenuation in the planar waveguide. In this study, we report a low propagation loss of 2.2 ? 0.2 dB/cm obtained in a PbTiO(3) optical waveguide.     

Fabrication and characterization of epitaxial Ba0.7Sr0.3TiO3 thin films for optical waveguide applications

The optical properties of barium strontium titanate (Ba0.7Sr0.3TiO3; BST) thin films are described. The BST thin films were epitaxially grown upon MgO (001) substrates by pulsed laser deposition. The crystallographic properties of the BST thin films were examined by x-ray diffraction. The BST thin films were highly optically transparent in the visible region. The optical waveguide properties were characterized by a prism coupling technique. An inverse-WBK method was employed to determine the refractive-index profile along the thickness of the BST films. Optical losses were measured by a moving fiber method, and the optical losses were found to be 0.93 dB/cm for the TE0 mode and 1.29 dB/cm for the TM0 mode at 1550 nm. Electro-optic (E-O) properties were measured by a phase-modulation detection method at 632.8 nm, and the BST films exhibited a predominantly quadratic E-O effect with a quadratic E-O coefficient of 6.64 x 10(-18) m2/V2.     

Preparation of ferroelectric NaNbO(3) thin films on MgO substrate by pulsed laser deposition

We successfully fabricated good quality NaNbO(3) (NN) films on MgO substrate by pulsed laser deposition using a K-Ta-O (KTO) buffer layer. An SrRuO(3) (SRO) lower electrode layer was deposited on a KTO buffer layer/(100)MgO substrate and then the NN film was deposited on top. X-ray diffraction showed that the SRO and NN films were epitaxially grown on (100)MgO substrate. Transmission electron microscopy showed a crystallographic relationship of [001](NN)//[001](MgO) between NN and MgO. The relative dielectric constant, epsilon(r), and dielectric loss, tan delta, of the film were 350 and 0.05 at 1 kHz, respectively. The polarization vs. electric field (P-E) hysteresis loop of the NN film was characteristic of ferroelectric behavior.     

MOD法制备的Bi3.25Nd0.75Ti3O12薄膜的铁电各向异性行为

采用金属有机分解法(MOD)在(111)Pt／Ti／SiO2／Si衬底上制备了含(117)成分的c轴择优取向和α轴择优取向的Bi3.25Nd0.75Ti3O12(BNT)薄膜．实验发现，BNT薄膜的品型结构主要依赖于预退火条件．电学性能测试表明，α轴择优取向的BNT薄膜具有高的剩余极化和矫顽场，较高的介电常数和介电损耗，以及较大的电容调谐率；而c轴择优取向的则相反．BNT薄膜具有同Bi4Ti3O12(BIT)薄膜相似的铁电各向异性行为．     

Electromechanical properties of fine-grain, 0.7 Pb(Mg(1/3)Nb(2/3))O3-0.3PbTiO3 ceramics

A fine grain, relaxor-based piezoelectric ceramic 0.7 Pb(Mg(1/3)Nb(2/3))O3-0.3PbTiO3 (PMN-30% PT) has been investigated, which was fabricated using the columbite precursor method. The complete set of electromechanical properties of the piezoceramic at room temperature is determined using a combination of ultrasonic and resonance techniques. This fine-grain ceramic (grain size < or = 2.5 microm) exhibits ultra-high dielectric permittivity (epsilon33(T)/epsilon0 approximately 7000) and a high coupling coefficient k(33) (= 0.78). Ultrasonic spectroscopy was used to measure the dispersion of the phase velocity and attenuation for the longitudinal wave propagating in the poling direction. Lower attenuation and smaller velocity dispersion were observed compared to modified Pb(Zr(x)Ti(1-x)O3 (PZT-5H) ceramics. The measurement results show that this fine-grain PMN-30% PT ceramic is a very good material for making ultrasonic array transducers.     

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.     

Fabrication and characterization of micromachined high-frequency tonpilz transducers derived by PZT thick films

Miniaturized tonpilz transducers are potentially useful for ultrasonic imaging in the 10 to 100 MHz frequency range due to their higher efficiency and output capabilities. In this work, 4 to 10-microm thick piezoelectric thin films were used as the active element in the construction of miniaturized tonpilz structures. The tonpilz stack consisted of silver/lead zirconate titanate (PZT)/lanthanum nickelate (LaNiO3)/silicon on insulator (SOI) substrates. First, conductive LaNiO3 thin films, approximately 300 nm in thickness, were grown on SOI substrates by a metalorganic decomposition (MOD) method. The room temperature resistivity of the LaNiO3 was 6.5 x 10(-6) omega x m. Randomly oriented PZT (52/48) films up to 7-microm thick were then deposited using a sol-gel process on the LaNiO3-coated SOI substrates. The PZT films with LaNiO3 bottom electrodes showed good dielectric and ferroelectric properties. The relative dielectric permittivity (at 1 kHz) was about 1030. The remanent polarization of PZT films was larger than 26 microC/cm2. The effective transverse piezoelectric e31,f coefficient of PZT thick films was about -6.5 C/m2 when poled at -75 kV/cm for 15 minutes at room temperature. Enhanced piezoelectric properties were obtained on poling the PZT films at higher temperatures. A silver layer about 40-microm thick was prepared by silver powder dispersed in epoxy and deposited onto the PZT film to form the tail mass of the tonpilz structure. The top layers of this wafer were subsequently diced with a saw, and the structure was bonded to a second wafer. The original silicon carrier wafer was polished and etched using a Xenon difluoride (XeF2) etching system. The resulting structures showed good piezoelectric activity. This process flow should enable integration of the piezoelectric elements with drive/receive electronics.     

Waveguiding properties of pulsed-laser deposition Ca4GdO(BO3)3 thin films

Waveguiding properties of stoichiometric Ca₄GdO(BO₃)₃ (GdCOB) thin films deposited on quartz substrates by the pulsed-laser deposition (PLD) technique are reported. The optical properties and the anisotropy of the obtained thin films are investigated using the prism-coupling technique. Refractive indices (n_x=1.666, n_y=1.673 and n_z=1.680 at 632.8 nm) were, respectively, determined from the transverse electric (TE) and the transverse magnetic (TM) mode excitations. These values are found to be 3% lower than those of the bulk material, which is likely due to the structural and morphological features of the deposited GdCOB films.