NKN [(Na,K)NbO3] is a candidate lead-free piezoelectric material to replace PZT [Pb(Zr,Ti)O3]. A single crystal has excellent piezoelectric-properties and its properties are dependent of the crystal orientation direction. However, it is hard to fabricate a single crystal with stoichiometrically stable composition due to volatilization of sodium during the growth process. To solve this problem, a solid solution composition is designed (Na,K)NbO3-Ba(Cu,Nb)O3 and solid state grain growth is studied for a sizable single crystal. Ceramic powders of (Na,K)NbO3-M(Cu,Nb)O3 (M = Ca, Sr, Ba) are synthesized and grain growth behavior is investigated for different temperatures and times. Average normal grain sizes of individual specimens, which are heat-treated at 1,125 oC for 10 h, are 6.9, 2.8, and 1.6 m for M = Ca, Sr, and Ba, respectively. Depending on M, the distortion of NKN structure can be altered. XRD results show that (NKN-CaCuN: shrunken orthorhombic; NKN-SrCuN: orthorhombic; NKN-BaCuN: cubic). For the sample heat-treated at 1,125 oC for 10 h, the maximum grain sizes of individual specimens are measured as 40, 5, and 4,000 m for M = Ca, Sr, and Ba, respectively. This abnormal grain size is related to the partial melting temperature (NKN-CaCuN: 960 oC; NKN-SrCuN: 971 oC; NKN-BaCuN: 945 oC).

Abstract
1. 서 론
2. 실험 방법
3. 결과 및 고찰
4. 결 론
References

• 정승운(인하대학교 신소재공학과) | Seungwoon Jung (Department of Materials Science and Engineering, Inha University)
• 임지호(인하대학교 신소재공학과) | Ji-Ho Lim (Department of Materials Science and Engineering, Inha University)
• 정한보(인하대학교 신소재공학과) | Han-Bo Jung (Department of Materials Science and Engineering, Inha University)
• 지성엽(인하대학교 신소재공학과) | Sung-Yub Ji (Department of Materials Science and Engineering, Inha University)
• 최승곤(인하대학교 신소재공학과) | Seunggon Choi (Department of Materials Science and Engineering, Inha University)
• 정대용(인하대학교 신소재공학과) | Dae-Yong Jeong (Department of Materials Science and Engineering, Inha University) Corresponding author