Temperature dependence of dielectric and ferroelectric properties for (1−x)Bi_0.5(Na_0.8K_0.2)_0.5TiO₃-xBaZn_0.5W_0.5O₃lead-free piezoelectric ceramics

Abstract

The ferroelectric and piezoelectric properties of (1¡x)Bi 0.5 (Na 0.8 -K 0.2 ) 0.5 TiO 3 -xBaZn 0.5 W 0.5 O 3 ((1¡x)BNKT-xBZW) ceramics have been studied to clarify the temperature dependence of the polarizationelectric field (P-E) hysteresis and dielectric properties. Based on the temperature dependence of the dielectric constant, it was found that the depolarization temperature (T d ) shifted to lower temperatures, depending on the composition x. The crystal structure refinement of (1¡x)BNKT-xBZW ceramics with rhombohedral and tetragonal phases revealed that the fraction of tetragonal phase to rhombohedral phase increased in the composition range of 0-0.05, which implies a formation of a morphotropic phase boundary (MPB). The piezoelectric constant (d 33 ) of the (1¡x)BNKT-xBZW ceramics increased with the composition x up to x D 0.05 and the maximum value was 168 pC/N. Such an increase in d 33 is attributed to the increase in the dielectric constant at room temperature which is due to the shift of T d ; a pinched P-E hysteresis loop was obtained at x D 0.05. The temperature dependence of the P-E hysteresis loops indicated that the shape of the hysteresis loop is closely related to the coexistence of ferroelectric and antiferroelectric phases.

Synthesis and piezoelectric properties of (1 −x)Bi0.5(Na0.8K0.2)0.5TiO3–xSr2ZrTiO6ceramics

“…It was found that the formation of MPB in the (1 − x)BNKT-xBa 2 ZnWO 6 system allows further enhancement of ferroelectric and piezoelectric properties (d 33 = 168 pC=N at x = 0.05). 24) In addition, Sr 2 ZrTiO 6 (SZT) 25) is also known as a double perovskite structure with a space group of I4=m and shows ferroelectric behavior, although ST and SZ show the paraelectric phases. Therefore, in order to clarify the influences of ferroelectric phase SZT addition on the piezoelectric properties, (1 − x)BNKT-xSZT ceramics were synthesized and the compositional dependence of piezoelectric properties was characterized in this study.…”