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Monoclinic (K,Na)NbO 3 Ferroelectric Phase in Epitaxial Films
Author(s) -
Luo Jin,
Sun Wei,
Zhou Zhen,
Lee HyunYoung,
Wang Ke,
Zhu Fangyuan,
Bai Yu,
Wang Zhan Jie,
Li JingFeng
Publication year - 2017
Publication title -
advanced electronic materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.25
H-Index - 56
ISSN - 2199-160X
DOI - 10.1002/aelm.201700226
Subject(s) - monoclinic crystal system , phase boundary , materials science , piezoresponse force microscopy , piezoelectricity , crystallography , ferroelectricity , phase (matter) , condensed matter physics , crystal structure , composite material , optoelectronics , chemistry , physics , dielectric , organic chemistry
Monoclinic phases, as intermediate phases at the morphotropic phase boundary, have been considered as the origin of high piezoelectricity in various piezoelectric systems. However, those monoclinic phases have seldom been experimentally observed at the phase boundary in lead‐free (K,Na)NbO 3 (KNN)‐based materials. This work shows that KNN epitaxial thin films demonstrate a monoclinic M C phase stabilized by elastic strain at room temperature, which is identified by both synchrotron X‐ray reciprocal space mapping and piezoresponse force microscopy. It is revealed that the piezoelectricity is greatly enhanced at 170 °C due to the monoclinic M C –M A phase boundary. The discovery of monoclinic phases in this work may open an avenue for developing a new thermotropic phase boundary in KNN‐based materials. The results also provide a guide for the exploration of high piezoelectricity driven by monoclinic phases in lead‐free piezoelectric materials.