Relaxor ferroelectric properties of the (1–2$x$)BiScO$_{3}$ $\cdot$ $x$PbTiO$_{3}$ $\cdot$ $x$PbMg$_{1/3}$Nb$_{2/3}$O$_{3}$ (0.30 $\le x\le$ 0.46) system

X-ray diffraction, dielectric, piezoelectric, and pyroelectric studies have been performed on ceramic samples of (1–2$x$)BiScO$_{3}$ $\cdot$ $x$PbTiO$_{3}$ $\cdot$ $x$PbMg$_{1/3}$Nb$_{2/3}$O$_{3}$ (0.30 $\le x\le$ 0.46) perovskite-like solid solutions. The solid solution symmetry was found to vary from the rhombohedral ($x\le$ 0.38) to tetragonal ($x\ge$ 0.42) as $x$ increases. The samples with 0.30 $<x\le$ 0.42 have properties characteristic of relaxor ferroelectrics, namely the existence of a wide peak in the temperature dependence of the dielectric permittivity at $T_{m\varepsilon}$ = 390–440 K that shifts to higher temperatures as the frequency increases, narrow unsaturated dielectric hysteresis loops, and an electric field-induced transition to the ferroelectric state at 318 K. The observed features of the dielectric, piezo-, and pyroelectric properties of these solid solutions are explained by the fact that they are relaxor ferroelectrics.