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

Abstract

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

Effect of phase distribution on dielectric properties of ferroelectric-dielectric composite ceramics

“…Many studies have shown that B-site cation ordering is the key to ensure the high Q of the material system. With the increasing ball-milling time, the ion diffusion effect in the system is continuously strengthened, and the gradually increasing doping effect destroys the harmony of the BST unit cell, which leads to the gradual decrease of the Q value at the microwave frequency [22,23].…”

Thermal oxidation of oxynitride films as a strategy to achieve (Sr2Ta2O7)100-x(La2Ti2O7)x based oxide perovskite films with x = 1.65

“…The purpose of the present study was to achieve a stoichiometric composition for STLTO oxide films and to characterize the dielectric properties of samples with the aim to emphasize high tunabilities of their permittivity as what was pointed out for STLTO dense ceramics [8,12].…”

“…Depending on the applications, these materials can be prepared in the form of single crystals, powders, ceramics or thin films. The oxide materials targeted presented in this paper show a layered perovskite structure and belong to the (Sr2Ta2O7)100-x(La2Ti2O7)x solid solution recently developed by our research team [8]. These original materials present interesting dielectric and ferroelectric properties, especially high tunabilities with potential applications in high frequencies tunable telecommunication devices.…”

“…We have demonstrated the ferroelectric behavior of this new family of compounds in the form of ceramics for compositions ranging from x = 0 to 5. Optimal performances were achieved for the composition x = 1.65: the permittivity value was ε' = 375 with tunability values T = 17.9 % at 4 kV/cm [8] and T = 55 % at 30 kV/cm (10 kHz, room temperature) [12]. The purpose of the present work is to produce this STLTO specific composition as a thin film.…”

Tunable TTB strontium and tantalum based thin films: Influence of the deposition parameters on the structural and dielectric properties

“…This meets the requirement for the formation of a solid solution between STO and LTO, thus offering the possibility of controlling the properties of the synthesized STLTO materials, especially their permittivity and tunability. We have demonstrated the ferroelectric behavior of the p-STLTO family of compounds in the form of ceramics for (Sr2Ta2O7)100-x(La2Ti2O7)x compositions with x ranging from 0 to 5 [7]. Optimal characteristics were achieved for x = 1.65: the permittivity value was ' = 375 with a high tunability T = 55 % at 30 kV/cm, 10 kHz and room temperature [8], associated to low dielectric losses tan = 2.10 -3 .…”