Improved temperature stability and high piezoelectricity in lead-free barium titanate-based ceramics

Enhanced temperature stability in the O–T phase boundary of (K, Na)NbO3‐based ceramics

“…Its trend of change is the same with the d 33 ( E ) value as a function of BNSZ content, and obtain the maximum ε ( E ) value of 2430 at the ceramics with x = 0.04. In addition, it is worth noting that the d 33 ( E ) and ε ( E ) values are sensitive to the type of phase boundary as well, and always getting the optimal value at the location of R‐T phase boundary …”

“…10,27 The variations in piezoelectric (d 33 , k p ) properties with composition BNZS have been displayed in Figure 6A, B. The d 33 and k p values vs. x first monotony increase at x = 0-0.04, and then monotony drop at x = 0.05-0.06, obtained relatively superior value (d 33 ~ 465 pC/N, k p ~ 0.51) in the composition of x = 0.04. The ε r value also has the similar change situation to the piezoelectric (d 33 , k p ) properties, and the tanδ takes the opposite to the variation in ε r value, getting a good dielectric performance (ε r ~ 3318, tanδ ~ 2.7%) in the samples of x = 0.04 (see Figure 6C, D).…”

“…Previous works reported that multiphase coexistence (particularly for R-T phase coexistence) provides more possible polarization directions, resulting in easy polarization rotation and enhanced domain density, which can greatly facilitate the polarization switching. 10 Therefore, the R-T phase coexistence has primary responsibility for the improvement of piezoelectric property (d 33 ) and dielectric property (ε r ). 2,10 Figure 7A exhibits the standard "butterfly shape" of bipolar electric field induced strain curves of KNNS-xBNZS ceramics with 0 ≤ x < 0.06, and a typical "sprout-shaped" of bipolar strain loop is obtained in the samples with x = 0.06, Such a phenomenon can be explained by the weak piezoelectric and ferroelectric properties.…”

“…The k p was measured by a resonance-antiresonance method with the impedance analyzer (Impedance Analyzer, PV70A). The d 33 was measured by the commercial Berlincourt-type of d 33 meter, (ZJ-3A) for the poled samples.…”

“…The enhanced electrical properties (eg, d 33 ~ 465 pC/N, ε r ~ 2759, S uni ~ 0.133%) is obtained in the ceramics with x = 0.04 because of the R-T phase boundary. In addition, the temperature stable of piezoelectric constant (d 33 or d 33 *) is measured by three distinctive methods (Quasi-static d 33 meter, Field-dependent piezoelectric coefficient d 33 (E) measurement, Piezoelectric strain S(E) measurement) in different phase boundaries (O, O-T, R-T) at the temperature range 20°C-180°C, revealing that the O-T phase boundary has a relatively good temperature stability. A mode is used to show how to effectively modified the piezoelectric constant (d 33 or d 33 *) and its temperature stability, we believe that such a strategy may further improve the temperature stability of d 33 or d 33 * value in KNN-based ceramics.…”