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  • 05월 20일 18시 이후 : 초록수정 불가능, 일정확인 및 검색만 가능

제125회 대한화학회 학술발표회 및 총회 Electrical properties and relaxor phase evolution of (Bi0.5Na0.5-xKx)TiO3 ceramics due to K ion substitution

2020년 5월 20일 16시 01분 50초
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Physical Chemistry
저자 및
Eunyoung Kim, Sang Don Bu*
Physics, Jeonbuk National University, Korea
Piezoelectric materials has been usefully applied to various devices such as sensor, nanopositioners, actuators, ultrasonic motors, fuel injectors and nanogenerators due to the converting between mechanical energy and electric potential energy. Up to now, the lead based piezoelectrics, Pb(Zr,Ti)O3 (PZT) material have played the dominant role in the device applications caused by their excellent performance. However, there is a big problem with harmful effects on the human body and the environment. The problem led us to prefer lead-free piezoelectric materials. Therefore, many researchers are now studying on the lead-free piezoelectric materials to find the alternative to replace PZT. Recent possibilities have been proposed in the Bi0.5Na0.5TiO3 (BNT)-based materials. Especially, large strains have been reported that are expected to be applied to actuators requiring fast and large movements in a specific composition. The cause of this large stain is known to be the formation of the ergodic phase of a relaxor ferroelectrics induced by an external electric filed. Therefore, we tried to study the large strain by substituting sodium for potassium in the lead-free relaxor BNT ceramics. In this study, we fabricated (Bi0.5Na0.5-xKx)TiO3 ceramics by using a conventional solid-state reaction method. We have investigated structural and electrical properties for x = 0.05 ~ 0.40. We found the coexistence of rhombohedral and tetragonal phase for all compositions. The percentage of tetragonal phase increased with increasing the composition of x. In the polarization–electric field (P-E) hysteresis loops measurement results show a change from a typical shape of ferroelectrics to pinch-type hysteresis shape after x = 0.1 composition. Also, the x composition of 0.1, the higher values of d33* (336 pm/V) is achieved due to large stain at room temperature. We note that the inverse piezoelectric response was improved about 6.6 times compared with x = 0.05 (d33* = 51 pm/V). These results suggest that the high temperature ergodic phase of BNT system is induced to room temperature through potassium substitution. Based on these results, the effects of ion substitution on the structure and electrical properties of BNT ceramics will be discussed.