Structure of Ferroelectric Silver Niobate AgNbO₃

Abstract

Crystal structure of ferroelectric silver niobate AgNbO3 was determined (Pmc21) by convergent beam electron, electron, neutron, and synchrotron diffraction techniques and first-principles calculations. The atomic displacements along the c axis in Pmc21 AgNbO3 are responsible for the spontaneous polarization, ferroelectricity, and the paraelectric−ferroelectric phase transition.

Complex antipolar2×4×22structure withPnmasymmetry inProsandeev1, Khalyavin2, Raevski3 et al. 2014Phys. Rev. B201120View full textAdd to dashboardCite

“…This antipolar structure has a rather interesting rotational octahedra (tilting) pattern of "+ + −−" type, where "+" stays for the clockwise and "−" for counterclockwise rotation of the oxygen octahedra, about the [010] p axis. A similar rotational pattern was observed in BiScO 3 thin films on SrTiO 3 [6], in (CaSr)TiO 3 [7], and in AgNbO 3 [8].…”

Ferroelectricity in Silver Perovskite Oxides

“…A cross (+) stands for the center of symmetry in the Pbcm structure. (by M. Yashima (Yashima et al, 2011) ).…”

“…Kania et al previously performed investigation on the dielectric behaviors and the differential thermal analysis for the Ag 1-x Na x NbO 3 solid solutions, and stated that the solid solution evolves from disordered antiferroelectric AgNbO 3 to normal antiferroelectric NaNbO 3 . As described in section §2.3, we now know that AgNbO 3 is not antiferroelectric but rather is ferrielectric at room temperature (Yashima et al, 2011). Moreover, recent reexamination on the polarization behaviors of stoichiometric and non-stoichiometric NaNbO 3 polycrystallines indicates that the reported clamping hysteresis loop of NaNbO 3 can be interpreted by pining effects while stoichiometric NaNbO 3 is intrinsically ferroelectric (Arioka et al, 2010).…”

“…The results on dielectric behaviors together with the reported phase transitions are summarized in Fig.8. Briefly speaking, the structures of the room-temperature (Yashima et al, 2011) and the high temperature phases (T> T O1-O2 =634 K ) (Sciau et al, 2004) are exactly determined, in contrast, those of low-temperature (T<room temperature) and intermediate phases ( T C FE =345 K <T< T O1-O2 ) remain to be clarified. In the dielectric curve, we can see a shoulder around 40 K. It is unknown whether this anomaly is related to a phase transition or not.…”

“…On the basis of this space group, M. Yashima (Yashima et al, 2011) exactly determined the atom positions (Table 1) in the structure using the neutron and synchrotron powder diffraction techniques. The atomic displacements are schematically shown in Fig.7.…”