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Two-dimensional (2D) Bi$_2$O$_2$Se semiconductor with a narrow band gap and ultrahigh mobility has been regarded as an emerging candidate for optoelectronic devices, whereas the ambiguous phonon characteristics and optical properties...

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As one of the classic antiferroelectrics, high complexity of a NaNbO3 structure sequence attracts great attention in the ferroelectric physics field. Here, temperature-pressure phase diagrams as a function of a CaSnO3 content for antiferroelectric (1-x)NaNbO3-xCaSnO3 ceramics have been improved by Raman spectroscopy. We clarify structural order of phase transitions on CaSnO3-modified NaNbO3 ceramics within the temperature range of 80–840 K by discussing the anomalies of lattice and phonon dynamics. The doping effect of CaSnO3 on the P-R phase transition has been summarized from the decreased critical temperature from 660 to 580 K. The intermediate phase at 480 K was recognized as an incommensurate phase. In addition, the anomalous pressure with respect to phonon frequency at the stress field of 0–25 GPa also provides the evidence of structural transformations at 6.55 and 10.05 GPa. Upon increasing the CaSnO3 content, phase transition moves to a lower pressure range. This work would provide the powerful supplement of phase transitions for the broad NaNbO3-based crystalline family with Raman scattering.

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