The present study reveals the ferroelectric nature of the novel (Sr 2 Ta 2 O 7 ) 100-x (La 2 Ti 2 O 7 ) x layered perovskite materials and highlights a large variation of their permittivity under electric fields associated with very low dielectric loss in the radio-frequency range. More precisely, an ideal solid solution has been evidenced within the composition range 0 ≤ x ≤ 5 with lattice parameters and cell volume varying linearly with x. The relative permittivity also depends on the composition and reaches a maximum value (365 @10kHz, RT), associated with a high tunability (17.6 % @0.38 kV/mm) with very low dielectric loss lower than 2.10 -3 . Variation of the relative permittivity as a function of the temperature is also demonstrated, with the existence of a temperature maximum, increasing with the composition. Polarization-electric field (P-E) measurements feature hysteresis loops for compositions x ≥ 1.85, in conjunction with current peaks in the I-E curves originating from ferroelectric domains switching.Keywords : perovskiteferroelectrictunability -Sr 2 Ta 2 O 7 -La 2 Ti 2 O 7

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A composite structure with an highly flexible polymer substrate and a thin film of lead zirconate titanate, Pb(Zr,Ti)O3 (PZT), is realized using an all‐chemical process. The fabrication of the structure comprises three steps: first, PZT is deposited on an aluminum thin foil, then the PZT thin film is bonded to a polymer, and, finally, aluminum foil is removed by selective chemical etching. Structural characterization techniques are used to ensure the quality of the PZT/polymer composite structure. Electrical measurements are also performed to confirm the ferroelectric characteristics of the composite. Finally, energy harvesting measurements are realized with interdigitated electrodes structure. A maximal energy density of 20 μJ cm−2 is obtained with manual mechanical excitation and an output voltage up to 35 V under free oscillations conditions in bending mode. This demonstrates that the recently developed PZT/polymer thin films are very promising for low‐frequency vibrating energy‐harvesting applications.