Structure and lattice dynamics of solid solutions $(1-x)$BiFeO$_3$–$x$ANbO$_3$ (A-K, Na)

The structures and the dynamic characteristics of the lattices of two compositions of solid solutions of multiferroic BiFeO$_3$ with ferroelectric KNbO$_3$ and antiferroelctric NaNbO$_3$, namely, $(1-x)$BiFeO$_3$–$x$KNbO$_3$ and $(1-x)$BiFeO$_3$–$x$NaNbO$_3$, have been studied using X-ray powder diffraction and Raman spectroscopy. For these systems with $x$ = 0.3, 0.5, and 0.7, the symmetry and unit cell parameters at room temperature have been determined. An analysis of the vibrational spectra has revealed sequences of rotational distortions with variations in the concentrations of components.