Origin of Giant Piezoelectricity in Pb[(Zn_1/3Nb_2/3)_0.91Ti_0.09]O₃ Single Crystals

Abstract

We found the giant electromechanical coupling factor of k₃₁ mode to be over 80% and the piezoelectric d₃₁ constant to be nearly −1700 pC/N in ferroelectric single crystals of Pb[(Zn_1/3Nb_2/3)_0.91 Ti_0.09]O₃ (PZNT91/09). The origin of the giant k₃₁ was as follows: the crystal with multi-domains changed into one having a mono-domain in the direction perpendicular to the poling field (k₃₁ mode) as well as in the direction parallel to the poling field. The discovery of the giant k₃₁ found a key to clarify the origin of the high piezoelectricity in PZNT91/09. Investigating the crystal orientation dependence of k₃₁ and their aging characteristics, the giant k₃₁ and d₃₁ accompanied with the superior aging characteristics could be obtained in the case of the rhombohedral (100) crystal poled along [001] of the original cubic direction. Furthermore, it is found that the Young's modulus Y (0.89×10¹⁰ N/m²) in rhombohedral PZNT91/09 with giant k₃₁ is remarkably small. Therefore, we believe that the high piezoelectricity including the giant k₃₁ in PZNT91/09 is due to the remarkable softness of the rhombohedral phase, not the existence of a M.P.B. for easy to deform symmetrically by poling field.

Keywords:

• Giant electromechanical coupling factor of k₃₁ mode
• giant piezoelectric d₃₁ constant
• lead zinc niobate titanate single crystal
• crystal plane dependence
• aging characteristics

ACKNOWLEDGMENTS

This work was partly supported by a Grant-in-Aid for Scientific Research (C) (No. 12650327) from the Ministry of Education, Culture, Sport, Science and Technology, the Research Foundation between Academy and Industry of Fukuroi City and the Murata Science Foundation. The authors would like to thank the Research Laboratory of Kawatetsu Mining Co., Ltd. for supplying the single-crystal samples.

Notes

**Weak impedance response not to calculate k₃₁