Effects of co-doped CaO/MnO on the piezoelectric/dielectric properties and phase transition of lead-Free (Bi0.5Na0.5)0.94Ba0.06TiO3 piezoelectric ceramics

Abstract

The piezoelectric properties of (1−x)(Bi 0.5 Na 0.5 ) TiO 3 -xBaTiO 3 ceramics were reported and their piezoelectric properties reach extreme values near the MPB (about x= 0.06). The X-ray analysis of (Bi 0.5 Na 0.5 ) 0.94 Ba 0.06 TiO 3 ceramics for all compositions exhibited a pure perovskite structure without any secondary phase. Within a certain ratio of contents, the co-doped ceramics enhanced piezoelectric coefficient (d 33 ), lowered the dielectric loss, and increased the sintered density. The temperature dependence of relative dielectric permittivity (K 33 T ) reveals that the solid solutions experience two phase transitions, ferroelectric to antiferroelectric and anti-ferroelectric to relaxor ferroelectric, which can be proven by P-E hysteresis loops at different temperatures. In addition, the specimen containing 0.04/ 0.01 wt.% CaO/MnO showed that the coercive field E c was a minimum value of 26.7 kV/cm, while the remnant polarization P r was a maximum value of 38.7 μC/cm 2 , corresponding to the enhancement of piezoelectric constant d 33 of 179 pC/N, electromechanical coupling factor k p of 37.3%, and relative dielectric permittivity K 33 T of 1137. (Bi 0.5 Na 0.5 ) 0.94 Ba 0.06 TiO 3 ceramics co-doped with CaO/ MnO were considered to be a new and promising candidate for lead-free piezoelectric ceramics owing to their excellent piezoelectric/dielectric properties, which are superior to an un-doped BNBT system.

The effect of pre-milling/pre-synthesis process and excess Ba on the microstructure and dielectric/piezoelectric properties of nano-sized 0.94[(Bi0.5Na0.5)TiO3]–0.06[Ba(1+x)TiO3]

“…13 shows the temperature dependence of the dielectric properties with various amounts of excess Ba. The dielectric behavior is rather analogous to those previously observed in BNBT ceramics with MPB compositions [30]. The inflection point designated T d in Fig.…”

Enhanced properties for ultrasonic transduction, phase transitions and thermal depoling in 0.96(Bi0.5Na0.5)TiO3-0.04BaTiO3 submicrometre-structured ceramics

“…Also, when comparing real values of all elastic s E ij coefficients and the frequency numbers it is observed that BNBT4 ceramic is similar to BNBT6 from the mechanical point of view, but the losses are also lower. Table III Besides these interesting properties and just as an example among the many studies on doping BNBT ceramics to enhance electromechanical performance, CaO/MnO co-doping [24] has shown efficiency in increasing d 33 , k p and k t . At the same time the depolarization temperature is almost unchanged, the sinterability increases and the grain size of the ceramics is reduced.…”

Perovskite Lead-Free Piezoelectric Ceramics

“…[8,12,17,19,21,22,24,25,28,36,37,43,46,47,54,60,62,63,67,69,76] According to Liu and Ren [27], a large piezoelectricity of this system is due to the existence of cubic-rhombohedral-tetragonal (C-R-T) triple point, as depicted in Fig. 9.4.…”

“…The transitions from cubic to tetragonal, tetragonal to orthorhombic, and then orthorhombic to rhombohedral occur at 435, 225, and À10 C, respectively [35,61]. KNbO 3 (KN) and NaNbO 3 (NN) can form a solid solution over the whole composition range and undergo similar structural phase transitions to KN upon [8,12,21,24,25,36,54,60,62,63,67,76] cooling (see Fig. 9.8).…”

“…9.10, the electromechanical coupling factors were found to decrease by 10% with thermal cycling as a result of cycling through regions with distinctly different domain configuration, significantly limiting their temperature range of operations [68]. [8,12,19,21,24,25,36,43,46,54,60,62,63,67,76] In an attempt to improve thermal stability and mitigate property degradation, further modification has been made on KNN system with the addition of calcium to the KNN system because calcium is known as an effective dopant to shift lower PPTs of BaTiO 3 downward without decreasing T C . Figure 9.11 shows the temperature-dependent properties of modified KNN system.…”