In this study, we investigated the microstructure and piezoelectric properties of 0.96(K0.456Na0.536)Nb0.95Sb0.05-0.04 Bi0.5(Na0.82K0.18)0.5ZrO3 (KNNS-BNKZ) ceramics based on one-step and two-step sintering processes. One-step sintering led to significant abnormal grain (AG) growth at temperatures above 1,085 °C. With increasing sintering temperature, piezoelectric and dielectric properties were enhanced, resulting in a high d33 = 506 pC/N for one-step specimen sintered at 1,100 °C (one-step 1,100 °C specimen). However, for one-step 1,115 °C specimen, a slight decrease in d33 was observed, emphasizing the importance of a high tetragonal (T) phase fraction for superior piezoelectric properties. Achieving a relative density above 84 % for samples sintered by the one-step sintering process was challenging. Conversely, two-step sintering significantly improved the relative density of KNNS-BNKZ ceramics up to 96 %, attributed to the control of AG nucleation in the first step and grain growth rate control in the second step. The quantity of AG nucleation was affected by the duration of the first step, determining the final microstructure. Despite having a lower T phase fraction than that of the one-step 1,100 °C specimen, the two-step specimen exhibited higher piezoelectric coefficients (d33 = 574 pC/N and kp = 0.5) than those of the one-step 1,100 °C specimen due to its higher relative density. Performance evaluation of magnetoelectric composite devices composed of one-step and twostep specimens showed that despite having a higher g33, the magnetoelectric composite with the one-step 1,100 °C specimen exhibited the lowest magnetoelectric voltage coefficient, due to its lowest kp. This study highlights the essential role of phase fraction and relative density in enhancing the performance of piezoelectric materials and devices, showcasing the effectiveness of the two-step sintering process for controlling the microstructure of ceramic materials containing volatile elements.

1. 서 론
2. 실험 방법
3. 결과 및 고찰
4. 결 론
Acknowledgement
References
<저자소개>

• 유일열(국립금오공과대학교 신소재공학과) | Il-Ryeol Yoo (School of Materials Science and Engineering, Kumoh National Institute of Technology, Gumi 39177, Republic of Korea)
• 박상현(국립금오공과대학교 신소재공학과) | Sang-Hyun Park (School of Materials Science and Engineering, Kumoh National Institute of Technology, Gumi 39177, Republic of Korea)
• 최성희(국립금오공과대학교 신소재공학과) | Seong-Hui Choi (School of Materials Science and Engineering, Kumoh National Institute of Technology, Gumi 39177, Republic of Korea)
• 조경훈(국립금오공과대학교 신소재공학과) | Kyung-Hoon Cho (School of Materials Science and Engineering, Kumoh National Institute of Technology, Gumi 39177, Republic of Korea) Corresponding author