Text this: Phase Transitions under the Electric Field in Ternary Ferroelectric Solid Solutions of Pb(In<sub>1/2</sub>Nb<sub>1/2</sub>)O<sub>3</sub>–Pb(Mg<sub>1/3</sub>Nb<sub>2/3</sub>)O<sub>3</sub>–PbTiO<sub>3</sub> near the Morphotropic Phase Boundary: Electric Approach