High-power Transducer Applications Research Articles

Mn-doped 0.15Pb(Yb1/2Nb1/2)O3–0.48Pb(Mg1/3Nb2/3)O3–0.37PbTiO3 piezoelectric ceramics for high performance high-power transducers

For high-power transducer applications, the piezoelectric materials should fulfill specific requirements of a high mechanical quality factor (Qm), a high piezoelectric strain coefficient (dij), and a high Curie phase transition temperature (Tc). In this study, we present an investigation of the structural, piezoelectric, and high-power characteristics of Mn-doped 0.15Pb(Yb1/2Nb1/2)O3–0.48Pb(Mg1/3Nb2/3)O3–0.37PbTiO3 (0.15PYN–0.48PMN–0.37PT) ceramics. The introduction of Mn dopants led to an increase in the tetragonal phase fraction within the 0.15PYN–0.48PMN–0.37 PT ceramics and the formation of oxygen vacancies, consequently significantly enhancing Qm due to their synergistic effect. Despite the hardening effect, the high value of the piezoelectric coefficient (d33) was maintained due to the increase in grain size. Particularly, the specimen doped with 3 mol% of Mn exhibited excellent piezoelectric properties of d33 = 345 pC/N, Qm = 1159, and Tc = 207°C. This specimen displayed a high vibration velocity of 0.6 m/s under the condition of equilibrium ΔT < 20°C (temperature rise from initial temperature), thereby confirming its immense potential for high-power transducer applications.

Abnormal piezoelectric properties of acceptor doped 0.75BF-0.25BT lead-free ceramics for application in atomizer

Ecologically sustainable hard type piezoelectric ceramics are highly demanded for high power transducer applications in replacing lead-based piezoelectric ceramics. In this study, MnO was proposed as acceptor dopant to modify the electric properties of 0.75BiFeO3-0.25BaTiO3 piezoelectric ceramics. Results showed that MnO doping reduced the lattice distortion of rhombohedral phase and facilitated the formation of pseudo cubic phase of 0.75BiFeO3-0.25BaTiO3 system. Moreover, it caused the diversity of domain morphology and reduced the domain size as well. XPS analysis indicated that Mn2+ ions suppressed the transition from Fe3+ ions to Fe2+ ions and gave rise to the increase of oxygen vacancies. Accordingly, the introduction of MnO synergistically increases the d33, Kp, and Qm and lowers the tanδ of 0.75BiFeO3-0.25BaTiO3 ceramics. The abnormal enhancement in hard type properties is ascribed mainly to the increase of extrinsic contribution rather than the pinning effect arising from oxygen vacancies. Finally, based on an optimal 0.75Bi(Fe0.985Mn0.015)O3-0.25BaTiO3 system, an atomizer prototype was fabricated. The remarkable atomization effect suggests a competitive potential of 0.75BF-0.25BT ceramic for transducer application.

Textured Mn-doped PIN-PMN-PT Ceramics: Harnessing Intrinsic Piezoelectricity for High-power Transducer Applications

Mn-doped PIN-PMN-PT ceramics were 90% [001]C textured by reactive templated grain growth (RTGG) with 5 vol% BaTiO3 microplatelets. Hardened properties such as high coercive field (EC) of 14 kV/cm, low dielectric loss (tan δ) of 0.37-0.66%, and high QM of 496 were obtained. Textured Mn-doped ceramics have TC of 219 °C, and a two times greater low-field d33* of 846 pm/V than random ceramics. Rayleigh analysis of textured PIN-PMN-PT ceramics shows that Mn-doping reduces the relative extrinsic contribution of the piezoelectric response to the strain behavior from 38% to 18% (at 4 kV/cm) by reducing irreversible domain wall motion. Mn-doping also reduced the overall strain response of PIN-PMN-PT, but crystallographic texturing increased the intrinsic piezoelectric response of the lattice as evidenced by the increase in d33 (Berlincourt) from 283 pC/N in random ceramics to 341 pC/N in textured ceramics. These results demonstrate that textured Mn-doped PIN-PMN-PT ceramics are excellent candidates for high-power transducer applications.

Finite-size-effect on a very large length scale in NBT-based lead-free piezoelectrics

[Formula: see text][Formula: see text]TiO3-based lead-free piezoelectrics are considered for potential replacement of the lead-based commercial piezoceramics in high-power transducer applications. We have examined the role of grain size in influencing the structural-polar inhomogeneity of stoichiometric and off-stoichiometric [Formula: see text][Formula: see text]TiO3 (NBT), and its morphotropic-phase-boundary (MPB) derivative 0.94[Formula: see text][Formula: see text]TiO3-0.06BaTiO3 (NBT-6BT). Our study reveals that size effect comes into play in these systems on a very large length scale (on the scale of microns) considerably affecting its global structure and properties.

Thermal conductivity of perovskite KTaO3 and PbTiO3 from first principles

The low thermal conductivity of piezoelectric perovskites is a challenge for high power transducer applications. We report first principles calculations of the thermal conductivity of ferroelectric PbTiO$_3$ and the cubic nearly ferroelectric perovskite KTaO$_3$. The calculated thermal conductivity of PbTiO$_3$ is much lower than that of KTaO$_3$ in accord with experiment. Analysis of the results shows that the reason for the low thermal conductivity of PbTiO$_3$ is the presence of low frequency optical phonons associated with the polar modes. These are less dispersive in PbTiO$_3$, leading to a large three phonon scattering phase space. These differences between the two materials are associated with the $A$-site driven ferroelectricity of PbTiO$_3$ in contrast to the $B$-site driven near ferroelectricity of KTaO$_3$. The results are discussed in the context of modification of the thermal conductivity of electroactive materials.

Preparation and characterization of Pb(Lu1/2Nb1/2)O3-Pb(Ni1/3Nb2/3)O3-PbTiO3 ternary ferroelectric ceramics with high piezoelectric constant

Pb(Lu1/2Nb1/2)O3-Pb(Ni1/3Nb2/3)O3-PbTiO3 ferroelectric ceramics were successfully prepared by a modified two-step columbite precursor method. The structural, dielectric, ferroelectric and piezoelectric properties were characterized by X-ray diffraction, ferroelectric and dielectric measurements. All the obtained samples have pure perovskite structure. The composition of 0.17PLN-0.47PNN-0.36PT within morphotropic phase boundary exhibits optimal properties with piezoelectric coefficient d33 = 378 pC/N, Curie temperature Tc = 142 °C, dielectric constant ε΄ = 4700, dielectric loss tangent tanδ = 0.05, remnant polarization Pr = 27.1 μC/cm2 and coercive field Ec = 8.89 KV/cm. According to Curie-Weiss Law and Lorentz-type quadratic relationship, the dielectric behavior was studied and the relaxor factor γ is between 1.55–1.87, indicating the character of diffuse phase transition of the Pb(Lu1/2Nb1/2)O3-Pb(Ni1/3Nb2/3)O3-PbTiO3 ceramics. The excellent piezoelectric properties and high Curie temperature make this system a promising material for high-power transducer applications in a broad temperature range.

Growth and characterization of high-Curie temperature Pb(Lu1/2Nb1/2)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 ternary single crystal by modified Bridgman technique

A new relaxor-based ferroelectric ternary system Pb(Lu1/2Nb1/2)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 (PLN–PMN–PT), with a combination of a high-Curie temperature system Pb(Lu1/2Nb1/2)O3–PbTiO3 (PLN–PT) and a high piezoelectricity system Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMN–PT), was investigated in this paper. Single crystal PLN–PMN–PT with dimensions of Φ20×45mm3 was grown successfully by the modified Bridgman technique for the first time. The studies of structure and composition of the as-grown crystal showed structural consistency but compositional deviation along the growth direction. The 〈001〉-oriented wafers of the PLN–PMN–PT single crystal showed excellent electrical properties at room temperature: ε33~4500, tanδ~0.5%, d33~2300pC/N. The crystal was found to exhibit high Curie temperature (TC~176°C), rhombohedral–tetragonal phase transition temperature (TRT~108°C) and coercive field (EC~8.1kV/cm), superior to those of PMN–0.3PT single crystal. Studies of temperature dependence ferroelectric properties showed that high values of k33 and d33 could be maintained up to the TRT. These results showed that PLN–PMN–PT piezoelectric single crystal has a higher Curie temperature and coercive field with excellent electrical properties, making the crystal a promising candidate for high-power transducer applications in a broad temperature range.

High temperature, high power piezoelectric composite transducers.

Piezoelectric composites are a class of functional materials consisting of piezoelectric active materials and non-piezoelectric passive polymers, mechanically attached together to form different connectivities. These composites have several advantages compared to conventional piezoelectric ceramics and polymers, including improved electromechanical properties, mechanical flexibility and the ability to tailor properties by using several different connectivity patterns. These advantages have led to the improvement of overall transducer performance, such as transducer sensitivity and bandwidth, resulting in rapid implementation of piezoelectric composites in medical imaging ultrasounds and other acoustic transducers. Recently, new piezoelectric composite transducers have been developed with optimized composite components that have improved thermal stability and mechanical quality factors, making them promising candidates for high temperature, high power transducer applications, such as therapeutic ultrasound, high power ultrasonic wirebonding, high temperature non-destructive testing, and downhole energy harvesting. This paper will present recent developments of piezoelectric composite technology for high temperature and high power applications. The concerns and limitations of using piezoelectric composites will also be discussed, and the expected future research directions will be outlined.

The role of tetragonal side morphotropic phase boundary in modified relaxor-PbTiO3 crystals for high power transducer applications

Morphotropic phase boundary (MPB) in ferroelectric materials leads to improved properties due to the structural instability. The manganese modified Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 crystals with MPB composition were investigated, the structure/property relationship was established. The tetragonal side MPB (coexistence of 91% tetragonal and 9% monoclinic phases) was confirmed by X-ray synchrotron data, while relaxor behavior was detected by Raman characterization and dielectric measurement. Crystals with such MPB composition possess high “figure of merit” (d33·Q33 ∼ 106 pC/N), being one order higher when compared with their pure rhombohedral counterparts. Together with high Curie temperature (∼229 °C) and temperature stability of properties, demonstrating a promising candidate for high power transducer applications.

Influence of manganese doping to the full tensor properties of 0.24Pb(In1/2Nb1/2)O3-0.47Pb(Mg1/3Nb2/3)O3-0.29PbTiO3 single crystals

Complete sets of elastic, piezoelectric, dielectric, and electromechanical properties of [001]c and [011]c poled pure and 0.5 wt. % manganese-doped 0.24Pb(In1/2Nb1/2)O3-0.47Pb(Mg1/3Nb2/3)O3-0.29PbTiO3 single crystals have been characterized at room temperature. The results indicate that manganese ion substitution in the B-site of perovskite 0.24PIN-0.47PMN-0.29PT single crystals makes the material harder with much higher mechanical quality factor Qm and slight decrease in piezoelectric and dielectric constants. The much improved Qm value (200-900) makes Mn-doped single crystals more suitable for high-power transducer applications than pure single crystals.

Design of low-loss 1-3 piezoelectric composites for high-power transducer applications.

Lead zirconate titanate (PZT)/polymer 1-3 composites have improved electromechanical properties compared with monolithic counterparts, but possess a low mechanical quality factor, limiting their use in high-power transducer applications. The goal of this work was to improve the mechanical quality factor of 1-3 PZT/polymer composites by optimizing the polymer materials. Theoretical analysis and modeling were performed for optimum composite design and various polymers were prepared and characterized. 1-3 piezocomposites were constructed and their electromechanical properties were experimentally determined. The results demonstrated that the composites with high-thermal-conductivity polymers generally have degraded electromechanical properties with significantly decreased mechanical quality factors, whereas the composites filled with low-loss and low-moduli polymers were found to have higher mechanical quality factors with higher electromechanical coupling factors: Q(m) ~ 200 and k(t) ~ 0.68 for PZT4 composites; Q(m) ~ 400 and k(t) ~ 0.6 for PZT8 composites. The improved mechanical quality factor of 1-3 piezocomposites may offer improved performance and thermal stability of transducers under high-drive operation.

Frequency dispersion of longitudinal ultrasonic velocity and attenuation in [001]c-poled 0.24Pb(In1/2Nb1/2)O3- 0.45Pb(Mg1/3Nb2/3)O3-0.31PbTiO3Single Crystal

The frequency dispersion of ultrasonic velocity and attenuation in [001](c)-poled 0.24Pb(in(1/2)Nb(1/2))O(3)-0.45Pb(Mg(1/3)Nb(2/3))o(3)-0.31PbTio(3) (PIN-0.45PMN-0.31PT) ternary single crystal were measured by ultrasonic spectroscopy from 25 to 100 MHz for the longitudinal wave. It was found that the velocity has a linear relationship with the frequency f, but the attenuation has a quadratic relation with f. The attenuation and frequency dispersion of the ternary system are lower than that of the (1-x)Pb(Mg(1/3)Nb(2/3))O(3)-xPbTiO(3) (PMN-PT) binary system and the coercive field also increased by a factor of 2.5, hence, the ternary single system is superior to the corresponding binary single-crystal system for high-frequency and high-power transducer applications.

Nonlinear behavior of BNT-based lead-free piezoceramics under various ac fields

In this study, two different bismuth sodium titanate (BNT) based lead-free piezoelectric ceramics, BNKBT-5 and BNKLBT-1.5, were fabricated and their nonlinear piezoelectric behaviour were compared. The ac field dependent piezoelectric properties of both lead-free materials were investigated. An analysis of the changes in real parts of the materials parameters (e.g. stiffness, permittivity and electromechanical coupling coefficient) and the loss factors have been determined by model fitting and the complex material parameters can be found. Under a high ac field, BNKBT-5 and BNKLBT-1.5 have different nonlinear behaviour. This characterization is necessary for using the lead-free piezoelectric ceramics in high power transducer applications.

Crystallographic dependence of loss in domain engineered relaxor-PT single crystals

Domain engineered 001 oriented relaxor-PbTiO(3) ferroelectric crystals exhibit high electromechanical properties and low mechanical Q values, analogous to "soft" piezoelectric ceramics. However, their characteristic low dielectric loss (</=0.5%) and strain-electric field hysteresis are reflective of "hard" piezoelectric materials. In this work, the electromechanical behavior of relaxor-PT crystals was investigated as a function of crystallographic orientations. It was found that the electrical and mechanical losses in crystals depends on the specific engineered domain configuration, with high Q observed for the 110 orientation. The high Q, together with high electromechanical coupling ( approximately 0.9) for 110 oriented relaxor-PT crystals, make them promising candidates for resonant based high power transducer applications.

Nonlinear behavior of piezoceramics and piezocomposites under various ac fields

A study is carried out to compare the nonlinear behavior of piezoceramics and piezocomposites. The complex material parameters including losses were determined by model fittings. An experimental system has been used to investigate the ac electric field dependence of the properties of the transducer materials, including lead zirconate titanate (PZT) and PZT/epoxy 1–3 composite rings. An analysis of the changes in the real parts of the material constants (i.e. stiffness, permittivity, and electromechanical coupling coefficients) and loss factors have been made. Under a high ac field, compared to PZT ceramics, the 1–3 composites were found to have different nonlinear behavior. This characterization is necessary for using the piezocomposite in high power transducer applications.

Nonlinear behavior of piezoceramics and piezocomposites under various ac fields

A study is carried out to compare the nonlinear behavior of piezoceramics and piezocomposites. The complex material parameters including losses were determined by model fittings. An experimental system has been used to investigate the ac electric field dependence of the properties of the transducer materials, including lead zirconate titanate (PZT) and PZT/epoxy 1–3 composite rings. An analysis of the changes in the real parts of the material constants (i.e. stiffness, permittivity, and electromechanical coupling coefficients) and loss factors have been made. Under a high ac field, compared to PZT ceramics, the 1–3 composites were found to have different nonlinear behavior. This characterization is necessary for using the piezocomposite in high power transducer applications.

Mn-Modified Pb(Mg1/3Nb2/3)O3–PbTiO3 Ceramics: Improved Mechanical Quality Factors for High-Power Transducer Applications

Piezoelectric ceramics are potential high-power electroacoustic sources, and have been studied for many years. However, when these devices are driven under high-level vibration, the electromechanical characteristics depart significantly from the conventional linear piezoelectric relationships due to the loss and nonlinear behavior in terms of elastic and dielectric properties. In this paper, we present results concerning the development of modified Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMN–PT) ceramics with improved mechanical quality factors for high-power application. We have focused efforts on base PMN–PT compositions close to the morphotropic phase boundary. Evidence will be presented which indicates that the improved mechanical quality factor results from the introduction of “hard” characteristics into PMN–PT by the substituents. Investigations of the nonlinearity of the electromechanical properties on the vibrational amplitude were performed using a constant displacement method. The degradation of the mechanical quality factor with increasing drive amplitude also presents thermal stability problems for the usage of these materials in high-power transducer applications.