Kim, Seungwook Kim, Min-Seop Lee, Chiho Park, Sungnam Cho, Won Il Kim, Woong 2024-01-20T01:04:11Z 2024-01-20T01:04:11Z 2021-09-05 2017-06-30 0925-8388 https://pubs.kist.re.kr/handle/201004/122607 Fundamentals in materials science are often based on understanding the relationships between the structures and properties of materials. Recently, our group reported on potassium niobate (KNbO3) nanowires with a metastable monoclinic phase that has never been observed before in bulk materials. In this paper, we report on the unique phase transition behaviors of these monoclinic nanowires and describe how their nonlinear optical properties are correlated with structural changes. The metastable monoclinic nanowires exhibit phase transition behaviors that are distinct from those of thermodynamically stable orthorhombic nanowires. The monoclinic nanowires undergo two phase transitions: monoclinic to tetragonal at 120 degrees C and tetragonal to cubic at 380 degrees C. In contrast, orthorhombic nanowires undergo phase transitions from orthorhombic to tetragonal and from tetragonal to cubic at 130 degrees C and 330 degrees C, respectively. The monoclinic and orthorhombic nanowires were found to exhibit clearly distinguishable variations in the second harmonic generation (SHG) intensity with variations in temperature. We show that the tetragonal structures derived from the monoclinic and orthorhombic phases are clearly different. The tetragonal phase derived from the monoclinic phase has higher spontaneous polarization and exhibits higher SHG intensity than the other tetragonal phase. Our analysis can be extended to explain the size-dependent properties of KNbO3. We calculated the spontaneous polarizations of the various phases based on the structural data and show how to use them to explain the above-mentioned structure-property relationships. The results of this study have important implications for both fundamental understanding and technological applications of metastable nanomaterials. (C) 2017 Elsevier B.V. All rights reserved. English ELSEVIER SCIENCE SA PIEZOELECTRIC PROPERTIES SPONTANEOUS POLARIZATION FERROELECTRIC KNBO3 ROOM-TEMPERATURE THIN-FILMS CRYSTALS SIZE CONSTANTS Structure-property relationship of metastable monoclinic potassium niobate (KNbO3) nanowires during phase transitions Article 10.1016/j.jallcom.2017.03.170 1 JOURNAL OF ALLOYS AND COMPOUNDS, v.709, pp.415 - 421 JOURNAL OF ALLOYS AND COMPOUNDS 709 415 421 scie scopus 000401042300050 2-s2.0-85015706198 Chemistry, Physical Materials Science, Multidisciplinary Metallurgy & Metallurgical Engineering Chemistry Materials Science Metallurgy & Metallurgical Engineering Article PIEZOELECTRIC PROPERTIES SPONTANEOUS POLARIZATION FERROELECTRIC KNBO3 ROOM-TEMPERATURE THIN-FILMS CRYSTALS SIZE CONSTANTS Nanowire Phase transition Metastable phases Perovskites Nonlinear