Electric‐Field‐Driven Phase Transition Process in (K, Na, Li)(Nb, Ta, Sb)O₃ Lead‐Free Piezoceramics

Abstract

The electric‐field‐driven phase transition in (K, Na, Li)(Nb, Ta, Sb)O3 lead‐free piezoelectric ceramics was investigated by X‐ray diffraction, Raman spectra, and the temperature dependences of permittivity spectra. After poling under different electric fields, phase of the ceramics transformed gradually from orthorhombic–tetragonal coexisting phase to orthorhombic phase, indicating that the crystal structure of ceramics was strongly sensitive to electric field as an external stimulus. A secondary phase K3Li2Nb5O15 induced by electric field was detected in the ceramics with Li content of 7 mol%, which was close to the solubility limit of lithium. This field‐induced secondary phase resulted from the movement of Li ions and the structural deformation induced by electric field. Moreover, piezoelectric constant d33 increased with the increasing poling field strength and the enhancement can be attributed to the field‐triggered domain switching. This study implied that in addition to temperature and composition, which has been reported in previous researches, electric field might be an effective way for inducing phase transition in lead‐free piezoelectric ceramics and improving the electrical performances simultaneously.

Effects of sintering temperature on structure and electrical properties of (Na0.48k0.473Li0.04Sr0.007)(Nb0.883Ta0.05Sb0.06Ti0.007)O3 piezoelectric ceramics

“…With the increase in sintering temperature above 1080°C, the piezoelectric properties weaken, similar to the previous results [18]. According to the experimental data and previous reports, the piezoelectric properties are dependent on the normal ferroelectric characteristics, density and grain uniformity [10]. The more normal ferroelectric characteristics, higher density and more uniform grains can enhance the piezoelectric properties with the increase in sintering temperature up to 1080°C [10].…”

“…According to the experimental data and previous reports, the piezoelectric properties are dependent on the normal ferroelectric characteristics, density and grain uniformity [10]. The more normal ferroelectric characteristics, higher density and more uniform grains can enhance the piezoelectric properties with the increase in sintering temperature up to 1080°C [10]. The Figure 10 shows the polarization-electric-field (P-E) hysteresis loops of the NKLNTS-ST ceramics (sintered at different temperatures) at room temperature at a frequency of 1 Hz.…”

“…Lim et al [9] and Feng et al [10] reported that the piezoelectricity also increases by incorporation of different dopants in the NKN ceramic structure as polymorphic phase boundaries (PPBs -coexistence of the orthorhombic and tetragonal phases) can be obtained at room temperature. Kim et al [11] reported that the electrical properties were improved and that the orthorhombic to tetragonal phase-transition temperature T O−T was decreased to room temperature when lithium, tantalum and antimony were added.…”

Temperature Dependent Piezoelectric Properties of Lead-Free (1-x)K0.6Na0.4NbO3–xBiFeO3 Ceramics

“…For K 0.5 Na 0.5 NbO 3 -based ceramics, the (200) doublet peak is usually considered to define the structure. For orthorhombic structure, I 002 /I 020 = 2:1 (I = intensity; Feng et al, 2016) but for the tetragonal structure, an opposite trend is observed, having I 002 /I 200 = 1:2 (Zhou et al, 2015). In our samples at x = 0, obvious split of the 200 peak was detected at 2θ ∼ 46 • which is consistent with the orthorhombic phase frequently reported for K 0.5 Na 0.5 NbO 3 ceramics (Sun et al, 2008).…”

Phase Structure Transformations and Electrical Properties of (Na0.52K0.4425)(Nb0.8925Sb0.07)O3–0.0375LiTaO3Ceramics According to Sintering Temperature

“…3 Li et al doped different dopants for the NKN ceramic system, and found that the polymorphic phase boundary (PPB) (the coexistence of the orthorhombic and tetragonal phases) can be obtained at room temperature, which enhances the piezoelectricity piezoelectricity. [4][5][6] Pang et al reported that the density and the piezoelectric properties of NKN-based ceramics can be improved by substituting Li, Ta, and Sb cations into the A and B sites, i.e. (Na 0.52 K 0.4425 )(Nb 0.8925 Sb 0.07 )O 3 -0.0375LiTaO 3 ceramics.…”