Large strain and high reversible dielectric tunability in Sm-modified PMN-PT ceramics

Relaxor ferroelectrics offer dynamic polar responses desirable for adaptive electronics, yet they are fundamentally constrained by a long-standing trade-off: compositions that deliver large electric-field induced strain typically suffer from pronounced hysteresis, while highly tunable ferroelectrics exhibit limited actuation capability. Here, we demonstrate a crossover composition-tuning strategy that helps balance these competing functionalities within a single perovskite platform. Using qualitative first-principles calculations on selected local-approximant supercells, we examined how Ti substitution affects possible local polarization tendencies in Sm-doped Pb(Mg_1/3Nb_2/3)_1-xTi_xO_3, including predominantly 〈110〉-like, mixed multidirectional and 〈001〉-like orientations. Near the relaxor crossover region (x = 0.16), the composition exhibits a strain of 0.31% and the highest reversible dielectric tunability of 76.4% under 2 kV mm^-1 with low remanent polarization and small irreversible tunability. Increasing the Ti content to x = 0.22 promotes a more stable polar state and yields a higher strain of 0.54%, but also increases remanent polarization and the irreversible tunability component, reducing the reversible dielectric tunability to 64.0%. Multiscale structural characterization supports composition-dependent evolution toward more spatially coherent local structural and polar responses with increasing Ti content. This work demonstrates composition tuning of local polar correlations near the relaxor crossover regime as an effective strategy for balancing high actuation, dielectric agility, and highly reversible field-induced response within a single compositionally tuned perovskite platform.