AUTHOR=He Ningbo , Li Cuiping , Lei Chihou , Liu Yunya 

TITLE=The morphologies of twins in tetragonal ferroelectrics

JOURNAL=Frontiers in Materials

VOLUME=9

YEAR=2022

URL=https://www.frontiersin.org/journals/materials/articles/10.3389/fmats.2022.1100964

DOI=10.3389/fmats.2022.1100964

ISSN=2296-8016

ABSTRACT=<p>Twins, as a special structure, have been observed in a small number of experiments on ferroelectrics. A good understanding of the morphologies of twins is very important for twin engineering applications in ferroelectric materials. In this work, the morphologies of twins in tetragonal ferroelectrics are investigated using the compatibility analysis of the transformation strains and spontaneous polarization and the energetic analysis. The tetragonal BaTiO<sub>3</sub> single crystal is chosen as an example for the material system. The results show that the lamellar twin structures with <inline-formula id="inf1"><mml:math id="m1" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mfenced open="{" close="}" separators="|"><mml:mrow><mml:mn>111</mml:mn></mml:mrow></mml:mfenced></mml:mrow></mml:math></inline-formula> as the twin plane have been identified by both compatibility analysis and energetic analysis, which is consistent with the experimental observations. In addition to <inline-formula id="inf2"><mml:math id="m2" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mfenced open="{" close="}" separators="|"><mml:mrow><mml:mn>111</mml:mn></mml:mrow></mml:mfenced></mml:mrow></mml:math></inline-formula> twin structures, <inline-formula id="inf3"><mml:math id="m3" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mfenced open="{" close="}" separators="|"><mml:mrow><mml:mn>1</mml:mn><mml:mover accent="true"><mml:mn>2</mml:mn><mml:mo>¯</mml:mo></mml:mover><mml:mn>1</mml:mn></mml:mrow></mml:mfenced></mml:mrow></mml:math></inline-formula> and <inline-formula id="inf4"><mml:math id="m4" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mfenced open="{" close="}" separators="|"><mml:mrow><mml:mn>2</mml:mn><mml:mover accent="true"><mml:mn>1</mml:mn><mml:mo>¯</mml:mo></mml:mover><mml:mn>5</mml:mn></mml:mrow></mml:mfenced></mml:mrow></mml:math></inline-formula> twin structures can also appear in tetragonal ferroelectrics. Furthermore, stable state uncharged twin boundaries and metastable charged twin boundaries are distinguished by energetic analysis, where the spontaneous polarization is compatible across the uncharged twin boundaries, while it is not compatible across the charged twin boundaries. The results predicted by the compatibility analysis and energetic analysis are consistent, thus providing a pathway for understanding the morphologies of twins.</p>