Temperature-dependent ferroelastic behaviour of antiferroelectric AgNbO3

The macroscopic ferroelastic response of polycrystalline AgNbO ₃ was investigated under the uniaxial compressive stress of up to -300 MPa from -150 °C to 450 °C, covering weak ferroelectric, antiferroelectric, and paraelectric phase regions. It is found that AgNbO ₃ exhibits ferroelasticity in the weak ferroelectric (M ₁), antiferroelectric (M ₂, M ₃), as well as the paraelectric regions (O and T), i.e. displaying ferroelastic hysteresis and remnant strain. The changes in mechanical parameters such as coercive stress, back switching strain, and remnant strain values reflect the specific crystal symmetry features at different phase regions together with the influence of temperature on domain wall motion. With stress removed and cooled down to room temperature, X-ray diffraction showed that the sample (at M ₁ state) exhibited different degrees of remnant domain textures and lattice strains, depending on its phase state when being compressed. Additionally, in situ stress- and temperature-dependent Raman spectroscopy measurements revealed that uniaxial compressive stress could induce changes in NbO ₆ octahedra and cation displacement, especially for high-temperature phases. Overall, the ferroelasticity, effects of stress on the structure and phase transitions offer opportunities for property engineering of AgNbO ₃ in capacitor applications.