Ferroelectricity and high tunability in novel strontium and tantalum based layered perovskite materials

The present study reveals the ferroelectric nature of the novel (Sr2Ta2O7)(100-x)(La2Ti2O7)(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 @10 kHz, 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.