BNT‐based ferroelectric ceramics: Electrical properties modification by Ta₂O₅ oxide addition

Abstract

Due to their superior piezo‐responses (strain S > 0.3%), bismuth sodium titanate (BNT)‐based relaxor ferroelectrics have received much attention. Compared to other chemical elements, tantalum (Ta) doping provides superior electro‐strain for these ferroelectrics, while the effect of Ta2O5 as oxide additive has been rarely reported. Herein, lead‐free piezoceramics of Bi0.5(Na0.72K0.22Li0.06)0.5TiO3‐xTa2O5 (BNKLT‐xTa2O5, x = 0‐0.015) are synthesized. We study the effects of Ta2O5 addition on the crystal structure, piezoelectric responses, dielectric properties, and ferroelectric properties of BNKLT ceramics. All of the ceramics exhibit a typical perovskite structure, and Ta2O5 diffuses into the BNKLT lattice to form a uniform solid solution. The addition of Ta2O5 can make the grains more regular and uniform, while excess Ta2O5 result in finer grains. The undoped BNKLT ceramics show good ferroelectric and piezoelectric properties (remnant polarization Pr = 22.5 μC/cm2 and piezoelectric coefficient d33 = 250 pC/N); however, the addition of Ta2O5 leads to an clear degradation in d33 and Pr. Meanwhile, the addition of an appropriate Ta2O5 amount leads to an increase in the electro‐strain, and the unipolar strain reaches 0.385% under 60 kV/cm for x = 0.003, together with a higher normalized strain (d33*=Smax/Emax) of 633 pm/V (x = 0.003). The enhanced strain behaviors can be attributed to the coexistence of the ferroelectric and relaxor states, and an excellent electrostriction coefficient Q33 (Q33 = S/P2) value of 0.038 m4C−2 is obtained under 60 kV/cm for x = 0.003.

Large electrostrictive coefficient with high electro‐strain dominated by modified ergodic state in BNT‐based solid solutions

“…The electrostrictive effect can be described by the equation S 33 = Q 33 · P 2 , where Q 33 is the longitudinal electrostrictive coefficient obtained by linear fitting S and P 2 4 . Therefore, seeking an effective way to simultaneously enhance the electrostrictive coefficient Q 33 and ferroelectric polarization P is the endeavor to obtain the superior electro‐strain responses, while these two parameters are often incompatible 4–40 …”

“…Comparison of lead‐contained, BT‐based, BNT‐based materials and this work against their (A) square of polarization vs electro‐strain 4‐8 and (B) electro‐strain vs electrostrictive coefficient Q 33 8–40 [Color figure can be viewed at wileyonlinelibrary.com]…”

Raman scattering and red emission of Mn4+ in La0.7Sr0.25Na0.05Mn0.7Ti0.3O3 manganite phosphor for LED applications

“…The X-ray structure analysis by the Rietveld renement was discussed in our previous work. 16 It was noted that LSNMT crystallizes in the rhombohedral R 3c structure without any detectable secondary phase, with lattice parameters a ¼ b ¼ 5.536(3) A, c ¼ 13.438(3) A and cell volume V ¼ 356.75(2) A 3 . It is also important to recall the values of the bond length d Mn-O-Mn ¼ 1.97(1) A and the bond angle q Mn-O ¼ 164.24 (3) .…”

“…Due to the warning from numerous research committees on pollution issues against the global industrial development, a clean nanotechnology system including multifunctional nanoparticles has become important owing to their potential applications in several research elds with actual and more efficient impacts in several areas of research. [1][2][3] More precisely, manganite-based perovskite-type oxides of the composition A 1Àx B x MnO 3 have appeared to be an attractive class of performing materials because of their low cost and abundance on the earth. 4,5 Their diversity and promising physical properties deserve signicant interest in numerous nanotechnology-related applications such as optoelectronic devices, electrocatalysis, and memory storage devices.…”

Temperature‐independent large strain with small hysteresis in Sb‐modified BNT‐based lead‐free ceramics

“…Owing to their large electro-strain, which is comparable to lead-based ceramics, BNT ceramics have been considered promising lead-free materials for actuator applications. [7][8][9][10][11][12] In the past, some useful methods have been used for tailoring the electro-strain properties in BNT-based ceramics, such as the addition of perovskite ABO 3 -type content, 13,14 cation doping at the A-site or B-site, 8,15 textured method, 9,16 and so on. 17,18 Among these chemical modification methods, Nb 5+ or Ta 5+ doping has proved to be the most effective for improving the electro-strain behavior of BNT-based ceramics.…”