Fig. 1: Strategies to enhance the electromechanical response in thin films.
From: Ultrahigh electromechanical response from competing ferroic orders
a, Effective piezoelectric coefficients \({d}_{33,f}^{* }\) of representative thin films from each design strategy (Extended Data Table 1). PTO, PbTiO3; BFO, BiFeO3; BTO, BaTiO3; KNN, K0.5Na0.5NbO3; PLZT, (Pb0.94La0.04)(Zr0.6Ti0.4)O3; Sm-PMN-PT, Sm-PbMg1/3Nb2/3O3-PbTiO3 (71/29); PZT, PbZr0.52Ti0.48O3; PZT (001), (001)-oriented PbZr0.52Ti0.48O3; NPR-NNO, NaNbO3 with nanopillar regions; PF-KNN, (K,Na)NbO3 with planar faults. AFE, antiferroelectric; and FE, ferroelectric. b, Phase transition of NNO from FE N phase (rhombohedral R3c) to AFE P phase (orthorhombic Pbcm) as temperature increases. FE and AFE phases coexist in bulk NNO between 12 K and 173 K. The purple and blue arrows, respectively, represent the polarization directions of the N and P phases. The top panel shows the schematics of Landau energy versus polarization in FE (left), FE and AFE coexistence (middle) and AFE (right) phases. c, Calculated free energy as a function of lattice constants (in pseudocubic lattice) for N and P phase NNO. Note that the intersection is located at about 3.9 Å, which guides us to choose SrTiO3 (STO) as the substrate for epitaxial growth. The insets show the schematics of crystal structures and octahedral rotations (Glazer’s notations) of NNO R3c and Pbcm phases. f.u., formula unit.
