Synthesis of antiferroelectric (Bi0.534Na0.5)0.94Ba0.06TiO3 ceramics with high phase transition temperature and broad temperature range by a solid-state reaction method

Abstract

Antiferroelectric 0.94(Bi 0.534 Na 0.5 )TiO 3 -0.06BaTiO 3 ceramics were prepared using a solid-state reaction method, involving the addition of excessive amounts of Bi 2 O 3 . The resulting ceramics featured a very high phase transition temperature (T m ~330°C), from the antiferroelectric to the paraelectric phase, and a low depolarization temperature (T d < 25°C). The broad temperature range, within which antiferroelectric properties are retained, of the prepared materials indicates their higher potential over lead-based antiferroelectric ceramics such as PZT-based materials that exhibit a lower T m ≤ 170°C. The lower T d and higher T m obtained values, relative to those reported in the literature, are believed to be due to the formation of A-site vacancies originating from the incorporation of excess Bi into the perovskite structure of the studied sample. In addition, the synthesized sample shows a high dielectric constant of ~1460, in a temperature range of 50-150°C at 1 kHz, and a high energy storage density of 0.71 J/cm 3 , which is an asset in energy storage capacitor applications. have been extensively studied and applied. However, the restricted use and elimination of toxic lead in these materials is underway in accordance to environmental legislation. Moreover, most PZT-based materials show low AFE-paraelectric (PE) phase transition temperatures, typically T m ≤ 170°C [10,11]. The low transition temperature limits the use of these materials in high temperature-related applications, thereby directing research to lead-free AFE materials with higher AFE-PE phase transition temperatures.In the past decades, (1-x)(Bi 0.5 Na 0.5 )TiO 3 -xBaTiO 3 (BNTxBT) lead-free ceramics have been thoroughly investigated [12][13][14]. Early studies showed that BNT-xBT ceramics exhibit a morphotropic phase boundary (MPB) between the FE rhombohedral phase (R3c) and the FE tetragonal phase (p4mm) at x ≈ 6 mol%. Furthermore, phase transition from FE to AFE, at the MPB, has been reported to occur at a relatively high depolarization temperature T d ~140°C [14]. Recently, Ma et al. [15] reported that at x = 0.06, phase segregation between the FE R3c and relaxor AFE P4bm phases preferentially takes place over phase separation between the FE R3c and FE P4mm phases. Also, transformation from the FE R3c to the relaxor AFE P4bm phase was reported to occur at a lower T d ~114°C [15]. To further reduce T d , Zhang et al.[16] studied K 0.5 Na 0.5 NbO 3 (KNN)-doped BNT-BT ceramics. Although the latter materials displayed AFE character at room temperature, the materials showed a low AFE-PE T m ~210°C. Recently, it was report-

The effects of Ba2+ content on depolarization temperature and pyroelectric properties of lead-free 0.94Na0.5Bi0.5TiO3–0.06Ba1+xTiO3 ceramics

“…/Na ? ) replacement and more ferroelectric domain wall stability [9,14,26]. The value of the T d of NBT-0.06BT in this work is close to that reported in the literature (*123°C) but the depolarization temperature of the NBT-0.06B 1?x T, (0.01 B x B 0.02) is lower than 123°C [27].…”

“…Table 2 also lists the p value (4.14 9 10 -4 C m -2°C-1 ) of a typical PZT ceramic measured at RT as a reference. The prepared NBT-0.06B 1?x T at x = 0.01-0.03 in this research show the comparable pyroelectric coefficients (3.30-3.5 9 10 -4 C m -2°C-1 ) [5,6,9].…”

“…Hence it is necessary to bring the phase transition temperature down to near room temperature (RT) for many applications, and that can be achieved by using various dopants [7]. In NBT-based systems, there is a weakly polar intermediate phase [8], which occurs between the depolarization temperature T d and the temperature of maximum permittivity (T m ) [9][10][11][12].…”

Large pyroelectric properties at reduced depolarization temperature in A-site nonstoichiometry composition of lead-free 0.94Na x Bi y TiO3–0.06Ba z TiO3 ceramics

“…. These vacancies can reduce ferroelectric long-range ordering and weaken the coupling between A-site ions and TiO 6 octahedron, as a result inducing the phase change at lower temperature [29,44]. Our results agree with the literature but also reveal that the T d can be reduced and shifted towards lower temperature not only by changing the Bi 3?…”

“…rather than B-site Ti 4? [29,44] as discussed before, which may result in the generation of some of the A-site vacancies when Bi 3? replaces Na ?…”