Stephen F. Poterala

⟨001⟩ textured (K0.5Na0.5)(Nb0.97Sb0.03)O3 piezoelectric ceramics with high electromechanical coupling over a broad temperature range

⟨001⟩-oriented (K0.5Na0.5)(Nb0.97Sb0.03)O3 (KNNS) ceramics with a narrow orientation distribution (full width at half maximum=7.0°) were produced by templated grain growth using NaNbO3 templates. Excellent electromechanical properties were obtained from −70 °C to the polymorphic phase transition (PPT) at 160 °C. Textured KNNS ceramics show very high electromechanical coupling factors kp=0.64 and k31=0.37, high piezoelectric constants d33=208–218 pC/N and d31=−82 pC/N, and modest strain hysteresis (6.3%) at room temperature. These properties are superior to those of randomly oriented KNN-based ceramics with similar PPT temperatures.

Microstructure development and piezoelectric properties of highly textured CuO-doped KNN by templated grain growth

This paper demonstrates the production of 〈00l〉-oriented CuO-doped (K0.476Na0.524)NbO3 (KNN) piezoelectric ceramics with a polymorphic phase transition (PPT) temperature greater than 180 °C by templated grain growth (TGG) using high aspect ratio NaNbO3 template particles. A novel (to the KNN system) two-step sintering and annealing process combined with CuO doping is demonstrated to improve density and maximize texture quality (F00l = 99% and rocking curve FWHM = 6.9°) in textured KNN ceramics. The best electromechanical properties (kp ≈ 0.58, k31 ≈ 0.33, d33 ≈ 146 pC/N, To-t ≈ 183 °C, Tc ≈ 415 °C, er = 202, and tan δ = 0.016) are achieved in 1 mol% CuO-doped KNN with F00l = 99% and a relative density of 96.3%. The values of d33, kp, and k31 are 70–90% higher than randomly oriented ceramics and are obtained without a significant reduction in the PPT temperature, resulting in stable piezoelectric performance over a wide temperature range (−50 to 180 °C). These results show that high-quality textured KNN can be obtained by TGG and that a reactive matrix is unnecessary.

Processing, texture quality, and piezoelectric properties of C textured (1-x)Pb(Mg1/3Nb2/3)TiO3 - xPbTiO3 ceramics

This paper describes the link between texture quality and electromechanical properties for C textured, 0.03(Na1/2Bi1/2)TiO3 - 0.97[0.715Pb(Mg1/3Nb2/3)TiO3 - 0.285PbTiO3] (0.03NBT-0.97[PMN-28.5PT]) ceramics with and without Mn-doping. Here, the subscript C denotes pseudocubic indices. Textured ceramics were prepared by templated grain growth of PMN-25PT on platelet-shaped 0.4(Na1/2Bi1/2)TiO3-0.6PbTiO3 (NBT-0.6PT) templates. Texture fractions of f = 0.92 (for undoped (1-x)Pb(Mg1/3Nb2/3)TiO3-xPbTiO3 (PMN-PT)) and f = 0.49 (for Mn-doped PMN-PT) were determined by fitting 002C XRD pole figures to the March-Dollase model, which was modified to account for symmetry-related 200C and 020C reflections. Using resonance methods, the elastic constants cij, sij, piezoelectric constants dij, eij, gij, hij, dielectric constants ɛij, and coupling coefficients kij of textured PMN-PT ceramics were characterized. It was found that the properties of textured PMN-PT approach the single crystal values along the texture axi...

Fabrication and properties of radially 〈001〉C textured PMN-PT cylinders for transducer applications

〈001〉C Textured PMN-PT ceramics have electromechanical properties (d33 = 850–1050 pm/V, k33 = 0.79–0.83) between those of conventional PZT ceramics and relaxor PMN-PT crystals. In this work, we tailor crystallographic orientation in textured PMN-PT ceramics for transducer designs with non-planar poling surfaces. Specifically, omni-directional cylindrical transducer elements were fabricated using monolithic, radially 〈001〉C textured and poled PMN-PT ceramic. Texture was produced by templated grain growth using NBT-PT templates, which were oriented radially by wrapping green ceramic tapes around a cylindrical mandrel. Finished transducer elements measure ∼5 cm in diameter by ∼2.5 cm in height and demonstrate scalability of textured ceramic fabrication techniques. The fabricated cylinders are ∼50 vol. % textured and show high 31-mode electromechanical properties compared to PZT ceramics (d31 = −259 pm/V, k31 = 0.43, ɛT33 = 3000, and Qm = 350). Frequency bandwidth is related to the square of the hoop mode cou...

Electric-field-induced phase switching in textured Ba-doped bismuth ferrite lead titanate

The template grain growth technique was used to synthesis textured 60BiFeO3-PbTiO3 (60:40BFPT) by using platelets of BaTiO3 as template. Synchrotron measurement clearly showed textured 60:40BFPT. Moreover, in situ high energy synchrotron radiation was employed to investigate the influence of an external electric filed on crystallographic structure of mixed phase 60:40BFPT. Application of an electric field ≥ 1 kV/mm resulted in phase transformation from mixed rhombohedral/tetragonal phases (≈ 73.5% tetragonal / 26.5% rhombohedral) to predominately tetragonal phase (≈ 95%) at applied field of 6 kV/mm.

Synchrotron texture analysis of thick BiFeO 3 -PbTiO 3 layers synthesised by tape casting using Aurivillius and non-Aurivillius templates

The solid solution between bismuth ferrite and lead titanate (xBiFeO₃-(1-x)PbTiO₃ or BFPT) possesses a morphotropic phase boundary (MPB) between the rhombohedral and tetragonal forms at x=0.7. It is of interest to investigate the influence of field-driven rhombohedral-tetragonal phase transitions across the MPB, to determine whether correctly oriented BFPT can provide both giant piezoelectric properties and significant magnetoelectric coupling. Here, we used the reactive templated grain growth (RTGG) technique to prepare crystallographically textured 0.6BiFeO₃-0.4PbTiO₃ (60:40 BFPT) ceramics. Both Aurivillius structure templates (Bi₄Ti₃O₁₂ and PbBi₄Ti₄O₁₅) and perovskite templates (BaTiO₃ and SrTiO₃) were used to prepare textured 60:40BFPT. Synchrotron radiation experiments were used to determine the degree of texture. A current data suggests that only BaTiO₃ templates survive the sintering process, and other candidate template materials reacted with the 60:40BFPT matrix at high temperature. In the case of SrTiO₃, this reaction results in a low Curie temperature (T_c = 350°C) due to the substitution of Sr²⁺. Aurivillius templates resulted in high Curie temperatures (610°C) and may be chemically suitable if they could be stabilized during the sintering process. However, the resulting ceramics show low remanent polarization (P_r = 3 μc/cm²), while SrTiO₃ and BaTiO₃ templated ceramics show higher remanent polarizations of 36 and 30 μc/cm², respectively. Because of their high chemical stability in this system, BaTiO₃ templates appear to be the best candidate for fabricating textured BFPT by the TGG method, displaying a high degree of crystallographic texture.

Texture analysis of thick bismuth ferrite lead titanate layers

The template grain growth technique was used to synthesis textured 60BiFeO3-PbTiO3(60:40BFPT) by using platelets of BaTiO3 as template. Synchrotron measurement clearly showed textured 60:40BFPT. Moreover, in situ high energy synchrotron radiation was employed to investigate the influence of an external electric filed on crystallographic structure of mixed phase 60:40BFPT. Application of an electric field ≥ 1 kV/mm resulted in phase transformation from mixed rhombohedral/tetragonal phases (≈ 73.5% tetragonal / 26.5% rhombohedral) to predominately tetragonal phase (≈ 95%) at applied field of 6 kV/mm. A crystallographic texture refinement was done by using software package materials analysis using diffraction (MAUD) with a 4th order spherical harmonic orientation distribution function (ODF). This refinement was completed using a P4mm+Cm structure model. Texture coefficients were constrained such that the equivalent texture coefficients of each phase are the same. The resulting texture refinement determined that sample has a 1.3 multiples of random distribution (MRD) {100} crystallographic texture.