The method to distinguish two types of monoclinic phases (MA and MB) in perovskite crystals by polarized light microscopy was developed. The MA-type monoclinic phase was observed in xPb(In1/2Nb1/2)O3–yPb(Mg1/3Nb2/3)O3–zPbTiO3 ternary crystal by polarized light microscopy at room temperat...