Date of Completion

8-9-2019

Embargo Period

8-6-2024

Advisors

George A. Rossetti, Jr.; Adam A. Heitmann; Bryan D. Huey

Field of Study

Materials Science and Engineering

Degree

Master of Science

Open Access

Campus Access

Abstract

High-performance piezoelectric materials are essential to the continuous development of state-of-the-art transduction devices of vital importance in naval applications. At the top of the acoustic performance echelon, high-coupling single crystals offer excellent source levels and sensitivity over a broad operational bandwidth. While ideal for high-demand, non-expendable applications, single crystals have not entirely displaced their cheaper conventional ceramic counterparts, which exhibit poorer coupling, higher elastic stiffness, and significantly lower piezoelectric coefficients. However, it is now possible to fabricate highly textured ceramics which promise high coupling and strain responses comparable to those of single crystals. In the modern undersea acoustic domain, tradeoffs among temperature stability, electromechanical performance, and manufacturing cost have substantial implications. This work constitutes a comparative study of Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) materials fabricated as-oriented single crystals,-textured unmodified and Mn-doped ceramics, and also conventional randomly oriented polycrystalline ceramics. The results of a detailed quantitative analysis of the phase transitions, thermal properties, and dielectric / electromechanical properties under weak-field and large-field conditions are used to provide performance-positioning comparisons for use in low and high frequency acoustic transducer designs which may be of interest for use in naval operating environments. The results show that there is no single material type having all of the desired qualities that factor into the design of these devices. Nonetheless, the textured ceramics possess superior values of coercive field and unipolar saturation strain, and also distinctly bridge the piezoelectric performance gap between single crystals and conventional ceramics. Furthermore, Mn-doping of textured ceramics provides additional property enhancements including reduced dielectric and mechanical losses, increased mechanical quality factors, and good thermal stability due to high rhombohedral-to-tetragonal phase transition temperatures. The combined results on these four sample types convincingly demonstrate that Mn-doped textured PMN-PT ceramics deliver many of the performance characteristics of single crystals, which can also be realized at a substantially reduced manufacturing cost.

Major Advisor

George A. Rossetti, Jr.

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