Interrelations Between Microstructure and Piezoelectric Sensitivity in Novel 0–3–0 Composites Based on 0.67Pb(Mg_1/3Nb_2/3)O₃ − 0.33PbTiO₃ Single Crystal

Abstract

This paper reports results on effective piezoelectric properties of advanced composites based on polydomain relaxor-ferroelectric single crystals of 0.67Pb(Mg_1/3Nb_2/3)O₃ − 0.33PbTiO₃. Two variants of the single crystal/porous polymer composite with 0–3–0 connectivity are proposed to study the role of microstructural factors in forming high piezoelectric sensitivity. The effective properties of the related 0–3 single crystal/polymer composite are predicted and considered to show ways of increasing the piezoelectric anisotropy and sensitivity. Examples of the volume-fraction and aspect-ratio dependences of the effective piezoelectric coefficients d _3j *, g _3j *, the hydrostatic piezoelectric coefficient g_h *, and squared figures of merit d ₃₃* g ₃₃* and d_h * g_h * of composites are analysed to show in which ranges high piezoelectric sensitivity is attained. The presence of single-crystal polydomain inclusions in the porous 3–0 matrix promotes the large effective parameters (g ₃₃* ∼ 10³ mV · m/N, g_h * ∼ 10³ mV · m/N, d ₃₃* g ₃₃* ∼ 10⁻¹⁰ Pa⁻¹, and d_h * g_h * ∼ 10⁻¹⁰ Pa⁻¹), and the obvious high-performance advantage of the 0–3–0 composites is discussed taking into account features of their microstructure.

Keywords:

• Composite
• relaxor-ferroelectric single crystal
• piezoelectric coefficients
• piezoelectric sensitivity
• squared figure of merit

PACS:

• 77.65.-j: Piezoelectricity and electromechanical effects
• 77.84.Lf: Composite materials
• 77.84.-s: Dielectric
• piezoelectric
• ferroelectric
• and antiferroelectric materials

Acknowledgments

The authors would like to thank Dr. C. R. Bowen (University of Bath, UK), Prof. Dr. I. A. Parinov (Southern Federal University, Russia), Prof. Dr. L. N. Korotkov (Voronezh State Technical University, Russia), Prof. Dr. A. S. Sidorkin and Prof. Dr. B. M. Darinsky (Voronezh State University, Russia) for their interest in the research problems on modern composite materials. The authors are grateful to the reviewer for useful comments and suggestions. This work was partially supported by the administration of the Southern Federal University (Project No. 11.1.09f on basic research), and this support is gratefully acknowledged by three of the authors (V. Yu. T., S. V. G. and A. A. P.).

Notes

It should be noted that the full sets of constants of the PZN–(0.06–0.07)PT SCs [9, 10] are characterised by a certain inconsistency. For example, elastic compliance s^E ₁₄ > 0 of the single-domain PZN–(0.06–0.07)PT SC [9] has the sign being opposite to that of s^E ₁₄ of the single-domain PMN–0.33PT SC [7]. If to take the matrix of elastic compliances ‖s^E ‖ of the single-domain PZN–(0.06–0.07)PT SC from Ref. 9 and change sgn s^E ₁₄ therein (i.e., taking s^E ₁₄ = −100.1^.10⁻¹² Pa⁻¹), then we obtain elastic moduli ‖c^E ‖ being in good agreement with those from Ref. 9. However, taking the matrices of ‖s^E ‖ and piezoelectric coefficients ‖d‖ [9], we evaluate the piezoelectric coefficients e_ij as follows: e ₃₁ = −4.62, e ₃₃ = 12.6, e ₂₂ = −25.9, and e ₁₅ = 28.7 (in C/m²). At the same time, the published piezoelectric coefficients e_ij [9] are e ₃₁ = −4.6, e ₃₃ = 12.6, e ₂₂ = 30.9, and e ₁₅ = 31.7 (in C/m²). It remains unclear a quantitative transition from e_ij to the piezoelectric coefficients h_ij in paper [9] where e ₂₂ > 0, but h ₂₂ < 0. Analysing the full set of electromechanical constants of the polydomain PZN–(0.06–0.07)PT SCs [10], one can state the inconsistency at the transition from ‖s^E ‖ and ‖d‖ to ‖e‖: according to our evaluations, e ₃₁ < 0, e ₃₃ < 0 and |e ₃₁|>|e ₃₃|, i.e., these constants are in disagreement with those published in Ref. 10. Other examples of the inconsistency were recently discussed in recent comment [12] on paper [13] where the full sets of electromechanical constants of [011]-poled PMN–(0.28–0.32)PT SCs were determined.