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Maximizing Strain Behavior and Minimizing Losses in Textured PIN-PMN-PT Piezoelectric ceramics

Author
Watson, Beecher H.
Published
[University Park, Pennsylvania] : Pennsylvania State University, 2020.
Physical Description
1 electronic document
Additional Creators
Messing, Gary L.
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Open Access.
Summary
PbTiO3-based perovskite ceramics represent a premier class of state-of-the-art materials used for piezoelectric applications such as actuators, high-power transducers, resonators, and ultrasonic motors. The high strain behavior and dielectric tunability of these materials also makes them highly competitive for sensor and hydrophone applications as well. The chemistries of next-generation materials are complex and their properties are highly sensitive to changes in processing which makes fabrication difficult. The greatest challenges to date are designing and processing materials that have high strain behavior as well as low dielectric and mechanical losses. In this document, new approaches to simplifying the manufacturing process, strategies for tailoring chemistry to reduce losses, and crystallographic texturing of ceramics for enhancing strain behavior are explored and discussed in detail. Finally, the intrinsic and extrinsic contributions to piezoelectricity of high-strain behavior textured ceramics are explored, setting the stage for a discussion of the development of the next-generation of high-performance piezoelectric ceramics. The effects of CuO-doping on perovskite phase formation and reactive sintering of 28Pb(In1/2Nb1/2)O3-40Pb(Mg1/3Nb2/3)O3-32PbTiO3 ceramics were investigated, and the densification kinetics were compared with conventionally sintered ceramics. CuO-doping was observed by in situ x-ray diffraction to accelerate perovskite and suppress pyrochlore formation. The 0.5 mol% CuO-doped PIN-PMN-PT ceramics sintered to >=95% density at temperatures as low as 790 °C. Comparable densification kinetics were observed with both conventional and reactive sintering. In the final stage of sintering, reactive sintering reduced the activation energy from 616 kJ/mol to 382 kJ/mol due to formation of a uniform 26-33 nm crystallite size microstructure that formed in situ at the onset of densification. Annealed reactively sintered ceramics also demonstrated equivalent ferroelectric behavior to conventionally sintered ceramics. The results demonstrate that reactive sintering is a novel approach to minimize material volatility during ceramic processing, an avenue for exploring co-firing with electrodes, as well as improved manufacturability through elimination of the perovskite powder synthesis step. Relationships between sintering temperature and annealing atmosphere on microstructure and dielectric, ferroelectric, and piezoelectric properties of reactively sintered CuO-doped Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (PIN-PMN-PT) ceramics were investigated. Uniform 2-3 [mu]m grain size, dense CuO-doped PIN-PMN-PT ceramics were obtained when oxygen sintered versus a bimodal grain size microstructure when sintered in air. Oxygen sintered ceramics have excellent properties including piezoelectric coefficient (d33) of 300-315 pC/N, coercive field (EC) of 7.7--8 kV/cm, and dielectric loss (tan [delta]) < 1.5%. The MPB region was mapped for ternary compositions doped with 0.5 mol% CuO and sintered in O2. MPB 25PIN-40PMN-35PT demonstrated the maximum piezoelectric properties with d33 of 565+/-23 pC/N and kp of 0.64+/-0.01. Sintering from 1050 °C to 1200 °C increased EC from 8.5 to 11.5 kV/cm and reduced tan [delta] from 1.8% to 0.8% by facilitating diffusion of CuO into the lattice and creating domain wall pinning defect dipoles as evidenced by an increase in the internal field bias of P-E loops. The effects of acceptor-doping with manganese as either MnO2 or MnNb2O6 with CuO on the dielectric, ferroelectric, and piezoelectric properties of PIN-PMN-PT ceramics were investigated. The 2% MnNb2O6-doped PIN-PMN-PT (6Pb(Mn1/3Nb2/3)O3-25Pb(In1/2Nb1/2)O3-34Pb(Mg1/3Nb2/3)O3-35PbTiO3) ceramics possessed hard properties such as high coercive field (EC) of 11.7 kV/cm, low dielectric loss (tan [delta]) of 0.7%, and high electromechanical quality factor (QM) of 1011. These properties were diminished in MnO2-doped ceramics because of lower oxygen vacancy defect concentration, and exaggerated grain growth resulted in >20 micron grain size. Co-doping with 2 mol% MnNb2O6 and 0.5 mol% CuO retained hardened properties such as high EC of 9.6 kV/cm, low tan [delta] of 0.6%, and high QM of 1029. MnNb2O6-doped and MnNb2O6+Cu co-doped ceramics display excellent figures of merit for resonance and off-resonance applications as well as high energy conversion efficiencies which make them promising candidates for high-power transducer elements. Mn-doped PIN-PMN-PT ceramics with 90% [001]C texture were textured by reactive templated grain growth (RTGG) with 5 vol% high aspect ratio BaTiO3 microplatelets. The 2 mol% Mn-doped textured ceramics possess hardened properties such as high coercive field (EC) of 14 kV/cm, low dielectric loss (tan [delta]) of 0.37-0.66%, and high QM of 496. Texturing suppressed permittivity variation near the TR-T transition, and Mn-doping increased the TC of textured PIN-PMN-PT from 212 °C to 219 °C relative to undoped PIN-PMN-PT. Textured Mn-doped ceramics have two times greater strain and low-field d33* of 846 pm/V than random ceramic. Rayleigh analysis of textured PIN-PMN-PT ceramics shows that Mn-doping reduces the extrinsic contribution of the piezoelectric response to the strain behavior from 38% to 18% (at 4 kV/cm) by reducing irreversible domain wall motion. Reduced irreversible domain wall motion is attributed to the formation of Mn_Nb^'-V_O^( ) defect dipoles that pin ferroelectric domains. Under low field conditions, domain pinning significantly reduced strain hysteresis from 29% to 9%. Mn-doping 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 indicate textured Mn-doped PIN-PMN-PT ceramics are promising candidates for low loss, high frequency, and high-power transducer applications.
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Dissertation Note
Ph.D. Pennsylvania State University 2020.
Reproduction Note
Microfilm (positive). 1 reel ; 35 mm. (University Microfilms 28778409)
Technical Details
The full text of the dissertation is available as an Adobe Acrobat .pdf file ; Adobe Acrobat Reader required to view the file.
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