PbTiO3 Single Crystals Research Articles

The influence of domain structures and phase transition on transmittance of PZN–PT ferroelectric crystal

A 0.93Pb(Zn1/3Nb2/3)O3–0.07PbTiO3(PZN–PT) single crystal was grown using the flux Bridgman method and 〈0 0 1〉-oriented slides were obtained. Strip-shaped and needle-shaped domains were observed in the same PZN–PT sample by a polarizing microscope. Raman spectra and transmittance spectra of regions with different domain structures have been measured. The Raman spectra exhibit slight differences in order information in different domain regions. The transmittance of strip-shaped domain regions is higher than that of needle-shaped domain regions, which means that the domain structures play a role in optical inhomogeneity. The temperature dependence of the domains and transmittance spectra has been investigated by in situ observation. The results show that the transmittance was influenced significantly by the ferroelectric phase transition, including the domain structure.

High pyroelectric power generation of 0.7Pb(Mg1/3Nb2/3)O3–0.3PbTiO3 single crystal

We report the pyroelectric power generation of a relaxor ferroelectric 0.7Pb(Mg1/3Nb2/3)O3–0.3PbTiO3 (PMN–PT) single crystal. For a temperature variation rate of 0.5 K/s, the PMN–PT generated a closed-circuit current of 10 nA and an open-circuit voltage of 1.1 V at room temperature. The pyroelectric current and voltage of the PMN–PT single crystal were proportional to the temperature variation rate and were sharply enhanced near the structural phase-transition temperature. Additionally, the PMN–PT pyroelectric generator produced stable power for excessive thermal cycling and was highly sensitive to random thermal fluctuations. Our results indicate the potential importance of PMN–PT for high-power pyroelectric generator applications.

Noise mechanisms investigation in pyroelectric infrared detectors based on Mn-doped Pb(Mg1/3Nb2/3)O3–0.27PbTiO3 vs. LiTaO3 single crystals

Different noise mechanisms between Mn-doped Pb(Mg1/3Nb2/3)O3–0.27PbTiO3 (Mn-PMNT) and LiTaO3 (LT) based pyroelectric infrared detectors were observed under voltage mode, revealing that at low frequency of 10Hz, dielectric loss noise dominates for Mn-PMNT based detectors, while resistance noise for LT based ones. Meanwhile, an extremely low equivalent voltage noise of appropriate 20nV/Hz1/2 was obtained in Mn-PMNT based detectors, 1/4 times lower than that of the LT based detectors. On the basis of the different noise mechanisms, frequency dependence of figure of merit for detectivity (Fd) have been deduced, providing significant reference values for the analysis of different materials based pyroelectric detectors.

Determination of full set material constants of [011]c poled 0.72Pb(Mg1/3Nb2/3)O3-0.28PbTiO3 single crystal from one sample.

0.72Pb(Mg1/3Nb2/3)O3-0.28PbTiO3 single crystals poled along [011]c have macroscopic orthorhombic mm2 symmetry. There are total 17 independent material coefficients for this symmetry so that the determination of self-consistent full matrix data is extremely difficult because many samples are needed and there is a large property variation from sample to sample. To overcome this self-consistency difficulty, we have developed a combined ultrasonic pulse-echo and impedance spectroscopy method, which can extract all coefficients from only one small sample. This method is especially useful for piezoelectric materials whose properties are strongly dependent on geometry and for crystals with only limited size available.

Thermal expansion and phase transition in [0 0 1]-oriented 0.69Pb(Mg1/3Nb2/3)O3–0.31PbTiO3 single crystal

The thermal expansion and phase transition of unpoled and poled [001]-oriented 0.69Pb(Mg1/3Nb2/3)O3–0.31PbTiO3 crystals are investigated using thermomechanical analysis, domain evolution, and dielectric measurement. Results of thermomechanical analysis show that the unpoled crystal exhibits negative thermal expansion at a temperature range from 30°C to 120°C, and the lattice parameter c of the tetragonal (T) phase is larger than those of the rhombohedral (R) and cubic (C) phases, i.e., cT>cR and cT>cC. Two additional structural modifications near 50°C and 125°C are detected in the unpoled crystal. Compared with that of the poled crystal, the T→C phase transition temperature of the unpoled crystal is relatively higher. An increase in temperature causes the unpoled crystal to undergo R→T→C phase transition, whereas R→M→T→C phase transition sequences are observed in the poled crystal. The phase transition behaviors are further verified by domain evolution and dielectric measurement. The significant differences between poled and unpoled crystals are attributed to the differences in their domain structures.

Refined crystal structures and phase transitions in 0.24Pb(In1/2Nb1/2)O3–0.43Pb(Mg1/3Nb2/3)O3–0.33PbTiO3 single crystal

Local lattice structures of 0.24Pb(In1/2Nb1/2)O3–0.43Pb(Mg1/3Nb2/3)O3–0.33PbTiO3 (0.24PIN–0.43PMN–0.33PT) single crystal have been investigated by Micro-Raman spectroscopy. A total of 12 Raman active modes were ascertained using the Gauss–Lorentzian line shape approximation, which confirmed that the 0.43PIN–0.26PMN–0.33PT single crystal has monoclinic symmetry at room temperature. The phase transitions were investigated by analyzing the temperature-dependent relative dielectric permittivity of both poled and unpoled 0.43PIN–0.26PMN–0.33PT single crystals measured upon heating. The monoclinic–tetragonal phase transition occurs at TM–T = 82 °C, and the Curie temperature is 199 °C. The splitting of (200) and (002) peaks in detailed X-ray diffraction spectra in the 2θ range of 44.6–45.2° during heating from room temperature to 200 °C was also studied. For a sample being poled along [111]c pseudo-cubic direction, several sharp peaks arise in the thermally stimulated depolarization current from 67 to 82 °C with the main peak occurs at 67 °C, which indicates that the depolarization temperature is 15 °C lower than the monoclinic to tetragonal phase transition and there are coexistence of monoclinic and rhombohedral phases in the [111]c poled single crystal.

Cryogenic motion performances of a piezoelectric single crystal micromotor

This study investigates the cryogenic performances of a millimeter-size piezoelectric ultrasonic linear micromotor. The piezoelectric vibrator of the micromotor is made of Pb(In1/2Nb1/2)O3 -Pb(Mg1/3Nb2/3)-PbTiO3 single crystal and operated in first-bending wobbling mode. Experiments show that the piezoelectric single crystal micromotor works effectively even at extremely low temperature of −175 °C, although its resonance peaks vary with temperature significantly. This work confirms the feasibility of cryogenic operation of the piezo-micromotor, which is meaningful for aerospace or superconducting microwave application.

Influence of TEM specimen preparation on chemical composition of Pb(Mg1/3Nb2/3)O3–PbTiO3 single crystals

The influences of different transmission electron microscopy (TEM) specimen preparation techniques on the chemical composition of Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMN–PT) single crystals was studied. Ion-milled samples where no cooling with liquid nitrogen (L-N2) was applied show permanently changed composition also deep inside the bulk material. When the PMN–PT samples were cooled to L-N2 temperature during the ion-milling process and in addition lower accelerating voltages were used, the chemical composition was altered only in the thinnest parts close to the specimen edge. Samples prepared using only tripod polishing technique show compositional irregularities close to the specimen edge. For the preparation of lead-containing samples, such as PMN–PT single crystals, a combination of tripod polishing and short Ar-ion-milling at low accelerating voltages while cooling the samples to liquid nitrogen temperature proved to be the most suitable to obtain artefact-free electron-transparent TEM lamellae.

Energy harvesting using the FER–FEO phase transformation in [011] cut single crystal PIN-PMN-PT

This study addresses the effects of frequency and load resistance on energy harvesting using a mechanically excited ferroelectric rhombohedral to ferroelectric orthorhombic phase transformation in [011] cut Pb(In1/2Nb1/2)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 (PIN-PMN-PT) single crystals. The crystals were mechanically driven through the phase transformation, and voltage across a resistive load was measured. The effects of frequency and resistive load on the electrical energy generated were measured. Over the range of frequencies and load impedances tested, the crystals behaved as a charge source. The current increased linearly with frequency, and the voltage increased linearly with load impedance. Impedance matching to maximize the energy harvested is discussed. The energy harvested using the phase transformation was on average 27 times, with a peak of 108 times, the energy harvested using the same crystals operating in the linear piezoelectric regime under the same stress excitation amplitude.

Improved thermal stability of [0 0 1]c poled 0.24Pb(In1/2Nb1/2)O3–0.47Pb(Mg1/3Nb2/3)O3–0.29PbTiO3 single crystal with manganese doping

The temperature dependence of dielectric, piezoelectric, and electromechanical coupling properties of 0.5wt.% manganese-doped and undoped [001]c-poled 0.24Pb(In1/2Nb1/2)O3–0.47Pb(Mg1/3Nb2/3)O3–0.29PbTiO3 (0.24PIN–0.47PMN–0.29PT) single crystals has been investigated. Compared to the undoped single crystal, the Mn-doped 0.24PIN–0.47PMN–0.29PT demonstrated higher level of coercive field (9.8kV/cm), increased Curie temperature (187°C), improved mechanical quality factor Qm (196), decreased piezoelectric constant d33 and comparable electromechanical coupling factor k33, indicating hardening effects caused by the manganese ion substitution. More importantly, it was found that the Mn substitution significantly enhanced temperature stabilities of k33, d33 and Qm, leading to 30–40°C improvement of the usage temperature range. These results show the application potential of Mn-doped ternary PIN–PMN–PT single crystals for the high-temperature and high-power electromechanical devices.

Enhanced dielectric, pyroelectric and ferroelectric properties of Mn-doped 0.15Pb(In1/2Nb1/2)O3–0.55Pb(Mg1/3Nb2/3)O3–0.30PbTiO3 single crystals

Mn-doped 0.15Pb(In1/2Nb1/2)O3–0.55Pb(Mg1/3Nb2/3)O3–0.30PbTiO3 single crystals were grown by modified Bridgman technique. High dielectric peak temperature of 161°C, low dielectric loss of 0.03% and enhanced pyroelectric coefficient of 10.1×10−4C/m2K are observed. Effects of oxygen vacancies related to annealing atmosphere have been investigated to explain enhanced dielectric and pyroelectric properties. Detectivity figure of merit of 34.1×10−5Pa−1/2 is achieved for oxygen-annealed crystals, which is the highest value among reported PIMNT crystals. Two different linear relationships between the coercive field and frequency are observed to obey Merz’s law, which reveals the domain and polarization switching mechanism.

Structure, frequency dependent dielectric properties and domain configuration of PMN–PFN–PT single crystal

Pb(Mg1/3Nb2/3)O3–Pb(Fe1/2Nb1/2)O3–PbTiO3 (PMN–PFN–PT) single crystal was grown successfully from high temperature solution by slow cooling method. Structure, frequency dependent dielectric properties and domain configuration of [001]-oriented single crystal have been investigated. X-ray diffraction analysis showed that the as-grown single crystal had a pure perovskite structure with tetragonal symmetry at room temperature. The temperature dependent dielectric permittivity showed only one dielectric anomaly, indicating the ferroelectric–paraelectric phase transition. According to the modified Curie–Weiss relationship, as-grown PMN–PFN–PT single crystal was in an intermediate state between normal and relaxor ferroelectrics. Dielectric permittivity and loss of [001]-oriented PMN–PFN–PT single crystal at room temperature decreased sharply with increasing frequency, which were different from those of PMN–PT65/35 single crystal. Domain configuration of [001]-oriented PMN–PFN–PT single crystal was observed for the first time by using a polarized light microscopy (PLM). The extinction of 90° domains at P/A:0° revealed a tetragonal structure. Domains along (001) face exhibited a straight stripe-like morphology with domain size on the scale of 10μm in average, combining with some much smaller domains about 3–5μm in width at the intersection of domain blocks which helps to minimize its total energy.

Pb(Zn1/3Nb2/3)O3–PbTiO3single crystal and device development

This paper describes recent device developments with relaxor ferroelectric Pb ( Zn1/3Nb2/3) O3– PbTiO3(PZN–PT) single crystals carried out at Microfine Materials Technologies Pte. Ltd, Singapore. Promising [011]-poled transverse cuts of PZN–PT single crystals and the results on the effect of electric field and axial compressive stress on the rhombohedral-to-orthorhombic ( R – O ) phase transformation behavior of such cuts are presented and discussed. The single crystal devices described include a compact low-frequency broadband power-efficient underwater tonpilz projector, high sensitivity shear accelerometers and acoustic vector sensors (AVS). The unique characteristics offered by these PZN–PT single crystal devices are highlighted, which serve as examples of new-generation piezoelectric devices and systems for a wide range of demanding applications.

Ferroelectricity and magnetism in Pb(Fe0.5Nb0.5)O3–Pb(Yb0.5Nb0.5)O3–PbTiO3 single crystals

Domain structure, ferroelectric and magnetic properties of [001]-oriented multiferroic single crystals Pb ( Fe 0.5 Nb 0.5) O 3– Pb ( Yb 0.5 Nb 0.5) O 3– PbTiO 3 (PFN–PYN–PT) with various compositions were investigated with the purpose of understanding the ferroelectric and magnetic order. The samples were determined to be rhombohedral phase or coexistence of tetragonal and rhombohedral phases by means of X-ray diffraction analysis and optical study. Furthermore, the domain configuration in tetragonal phase always takes on 90° domain wall. All samples exhibit well-developed saturated hysteresis loop, indicating no substantial increase of conductivity despite the introduction of Fe 3+ ions. But the piezoelectric coefficients were reduced due to the introduction of PFN. In addition, the PFN–PYN–PT single crystals showed paramagnetic behavior, resulting from the – O – Fe 3+– O – Nb / Yb / Ti – O – Fe 3+– O – magnetic interaction. Interestingly, M–H hysteresis loops display a magnetic relaxor behavior.

Nanoscale domain structures in 0.91Pb(Zn1/3Nb2/3)O3-0.09PbTiO3 (91PZN-9PT) single crystals studied by piezoresponse forcemicroscopy

High-resolution domain studies have been performed in 91PZN-9PT single crystals by piezoresponse force microscopy. Nanometer- and micron-sized strip-shaped 180º and parallel 90º domains were observed in the rhombohedral (R) and tetragonal (T) phases. Domain patterns with the typical sizes 5–200 nm were observed on the (001)cub surface of unpoled sample. The existence of nanodomains in the sample is tentatively attributed to the relaxor nature of PZN-PT where small polar clusters may form under zero-field cooling conditions. The domain observation confirms the structure of the morphotropic 91PZN-9PT crystals, which is composed of both the R and T (or monoclinic) orientations states. The outstanding piezoelectric properties may result from the cooperative response of the microscale/nanoscale domain structure.

A novel thermally biased mechanical energy conversion cycle

This paper demonstrates a new power cycle for direct conversion of mechanical energy into electrical energy under a thermal bias. The cycle consisted sequentially of (i) an electric poling process under zero stress, (ii) an isoelectric process consisting of applying a uniaxial compressive stress σH followed by (iii) an electric de-poling process under constant compressive stress, and finally (iv) an isoelectric process consisting of removing the compressive stress. The new cycle was performed at constant bias-temperature Tb. It was demonstrated on [001]-poled 0.72PbMg1∕3Nb2∕3O3-0.28PbTiO3 single crystals. The power density increased with increasing cycle frequency and compressive stress for frequency up to 1 Hz. Maximum energy and power densities of 44 J/l/cycle and 44 W/l were achieved at 1 Hz for bias-temperature Tb of 80 °C and electric field cycled between 0.2 and 0.8 MV/m with compressive stress σH = 25.13 MPa. This was attributed to a tetragonal-monoclinic-orthorhombic phase transition sequence. The material efficiency reached up to 87% and exceeded that of a similar thermomechanical power cycle performed on pyroelectric material. Finally, a physical model predicting the power density was derived and yielded accurate predictions of experimental data for all bias-temperatures considered and cycle frequency up to 1 Hz.

Tuning the functional properties of PMN-PT single crystals via doping and thermoelectrical treatments

Single crystals based on solid solutions of lead-magnesium-niobate (PMN) and lead titanate (PT) have emerged as highly promising multifunctional systems combining piezoelectric, pyroelectric, and electro-optic properties that surpass by far those of the best known lead-zirkonium-titanate ceramics. In this paper we present new findings on how the phase transition temperature and the dielectric and ferroelectric properties can be tuned depending on crystal composition, orientation, and thermoelectrical treatment. Mn-doped and pure 0.72PbMg1/3Nb2/3O3-0.28PbTiO3 (0.72PMN-0.28PT) single crystals with ⟨111⟩ and ⟨001⟩ orientations were investigated. A special attention was devoted to field cooling (FC), i.e., cooling under electric field from different temperatures. The results illustrate different findings that were not reported before: the Curie temperature, i.e., ferroelectric-paraelectric transition temperature, is enhanced after field cooling of the Mn-doped, ⟨001⟩-oriented crystal while such a shift is not observed in the ⟨111⟩-oriented and the non-doped crystals. In addition, substantial polarization suppression occurs in the Mn-doped crystals upon FC from high temperature regardless of orientation. Based on piezoforce microscopy of the domain structure that shows suppression of domain growth following field cooling from 200 °C, we propose a mechanism for polarization suppression based on domain pinning by charged defects. The practical importance of our results lies in showing the opportunity offered by a proper choice of crystal composition and poling conditions for tuning the functional properties of PMN-PT single crystals for a specific application. This should contribute to the understanding of their properties towards advanced sensor and transducers devices.

Enhanced piezoelectric activity and temperature stability of [1 1 1]-oriented orthorhombic 0.68Pb(Mg1/3Nb2/3)O3–0.32PbTiO3 single crystals by domain size engineering

The dielectric and piezoelectric properties of [1 1 1]-oriented orthorhombic Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMN–PT) single crystals (3O multi-domain state) with various domain sizes were investigated by poling control. The free dielectric permittivity (e33T/e0) and longitudinal piezoelectric coefficient (d33) were 6400 and 900 pC N−1, respectively, for samples with domain sizes of ∼2 μm, nearly twice that of ∼20 μm. Together with good temperature stability (Δd33/d33(25°C)Δd33/d33(25°C) <8%) up to the orthorhombic–tetragonal phase transition temperature, the “3O” PMN–PT crystals with fine domain structures are promising candidate for sensors and transducers.

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.

Propagation of Shear Horizontal Waves in Laminated Composites Based on Differently Orientated Poled 0.72Pb(Mg1/3Nb2/3)O3-0.28PbTiO3 Single Crystals

The propagation characteristics of shear horizontal waves in [001]c, [011]c and [111]c direction polarized 0.72Pb (Mg1/3Nb2/3) O3-0.28PbTiO3 (PMN-0.28PT) piezoelectric single crystals/polymer periodic laminated composites are studied by using the global matrix method. The numerical results show that the piezoelectric effect has a significant influence on the bandgap width of the composite structure containing [011]c and [111]c poled PMN-0.28PT, but little effect on the band structure of the system containing [001]c poled single crystal. In addition, the first bandgap (FBG) width of the composite structure depends strongly on the poling directions when the filling fraction of PMN-0.28PT is larger than 0.5, and its FBG starting frequency displays no distinct difference among the three polarization directions at all filling fractions. The reported results provide valuable guidelines for designing filters and transducers made of composite structures containing relaxor-based ferroelectric single crystals.