Pressure-induced successive phase transitions and Fano resonance engineering in lead-free piezoceramics KNbO₃

We carried out detailed high-pressure Raman scattering studies on lead-free perovskite piezoceramics KNbO3 (KNO) with a smaller pressure interval so that the successive phase transition pressures are precisely determined (P-O?T: 8.2 GPa; P-T?C: 10.9 GPa). The pressure-quenched phase does not return to the ambient orthorhombic phase completely. In this work, the pressure-induced phase transition sequence is discussed in detail. Also, based on the pressure-dependent Raman spectra of KNO, we have discovered clear evidence of a pressure-induced Fano resonance. It reveals the role played by the Raman-active continuum and discrete energy states in the condensed matter system under high pressure and enables the high-pressure Fano resonances engineering in arbitrary geometries [q?(-8, 0)]. These findings highlight the opportunity for designing and tuning the wave transmission and optical switch properties of lead-free piezoceramics KNO via high pressure.