Morphotropic phase boundary (MPB) in ferroelectric materials leads to improved properties due to the structural instability. The manganese modified Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb 2/3)O3-PbTiO3 crystals with MPB composition were investigated, the structure/property relationship was established. The tetragonal side MPB (coexistence of 91% tetragonal and 9% monoclinic phases) was confirmed by X-ray synchrotron data, while relaxor behavior was detected by Raman characterization and dielectric measurement. Crystals with such MPB composition possess high "figure of merit" (d33· Q33 ∼ 106 pC/N), being one order higher when compared with their pure rhombohedral counterparts. Together with high Curie temperature (∼229 °C) and temperature stability of properties, demonstrating a promising candidate for high power transducer applications. © 2013 AIP Publishing LLC.