The electric field induced ferroelectric phase transition of AgNbO3

Abstract

Coexistence of two phases of AgNbO3 is shown to explain the experimentally observed polarization–electric field hysteresis loop better than either phase in isolation, based on detailed first-principles calculations of the structural changes and stabilities of different phases of this compound. Calculations confirm a ferroelectric phase transition, whereby the symmetry of the AgNbO3 crystal switches from antiferroelectric Pbcm to ferroelectric Pmc21, under an electric field of 9 MV/cm. The calculated spontaneous polarization (0.61 C/m2) under this field compares well with the experimental value of 0.52 C/m2. After transforming, the structure remains in the ferroelectric state even after the electric field is removed, despite the structure being energetically metastable. As the energy difference between the antiferroelectric and ferroelectric phases is only +0.5 meV/f.u. and the potential energy barrier between them (∼40 meV/f.u.) is comparable to thermal fluctuation energies, it is possible for these two phases to coexist at temperatures well below the paraelectric-antiferroelectric transition temperature (∼626 K). The exploitation of this phenomenon in AgNbO3 and related materials may provide a useful strategy for developing high-performance piezoelectric materials.

Polarization fluctuations in the perovskite-structured ferroelectric AgNbO3

“…DFT calculations of AgNbO 3 under an applied electric field showed that a fully FE structure, also belonging to space group Pmc2 1 , and which we refer to as the F phase, becomes stable, with a theoretical polarization value of 61 μC/cm 2 , in good agreement with the measured polarization under an applied electric field of 52 μC/cm 2 [19]. The F-Pmc2 1 structure is compared with M1-Pbcm and M1-Pmc2 1 structures in Fig.…”

Phase transitions in bismuth-modified silver niobate ceramics for high power energy storage

“…[13][14][15] However, the existence of polar regions at room temperature was ascertained by detailed diffraction studies has been reported more recently. 12,16,17 The coexistence of antiferroelectric (AFE) and FE states in AgNbO 3 yields a complicated sequence of electric field-induced events, as observed in the current-polarization-electric field hysteresis loops previously reported. 12 It was found that bismuth niobate, BiNb 3 O 9, crystalizes as an A-site deficient metastable perovskite super-cell structure (i.e., Bi 1/3 NbO 3 ).…”

Photoinduced Phase Transitions in Ferroelectrics

“…They exhibit a number of phases [14,15] associated with lattice instabilities of the reference cubic phase [16]. The transitions between phases are commonly driven by temperature [14,15], pressure [17][18][19], or static electric fields [20]. Here, we demonstrate that light can also act as a knob to control the crystal symmetry.…”