Intrinsic piezoelectricity in (K,Na)NbO3-based lead-free single crystal: Piezoelectric anisotropy and its evolution with temperature

Abstract

Searching for lead-free piezoelectric materials with a large piezoelectricity and excellent thermal stability has been a major concern in both scientific research and practical applications. To understand the mechanism of high piezoelectricity and its temperature-dependent behavior in lead-free materials, we focus here on the tetragonal (K,Na,Li)(Nb,Ta)O3 single crystal and investigate the intrinsic d33* along arbitrary directions as well as its evolution with temperature. The synergistic influence of several factors (narrow tetragonal temperature interval, sharp tetragonal-cubic phase transition, and large PS below TC) leads to a strong anisotropy in the d33* profile, while a high d33* is obtained around θ = 45° over a wide temperature range. This work comprehensively reveals the physical mechanism of piezoelectric anisotropy in lead-free materials, which provides vital information to design high-performance lead-free piezoelectric materials through orientation engineering and lattice manipulation, which is expected to benefit a wide range of piezoelectric materials.

Growth and characterization of large size lead‐free ferroelectric K(Ta,Nb)O3 single crystal

“…Based on the (110), (200), and (222) XRD peaks, the tetragonal unit cell parameters are calculated to be a = b = 3.9920 Å, and c = 4.0009 Å. In spite of the low T C , the KTN crystal demonstrates large tetragonal lattice distortion with c / a ‐1~0.0089, slightly lower than (K, Na, Li)(Nb, Ta)O 3 ( T C ~235℃) 6 and Pb(Nb 2/3 Mg 1/3 )O 3 ‐0.39PbTiO 3 ( T C ~177°C) 29 single crystals with high Curie temperature. Thus the reduced T C does results in a decreased tetragonality.…”

“…[1][2][3][4][5] Owing to the large piezoelectric coefficient and the excellent composition tunable property, the alkali niobate system, such as (K, Na)NbO 3 , KNbO 3 , etc., has been considered as the most promising lead-free candidate. [6][7][8][9][10] Saito et al and Wu et al have demonstrated that partial substitution of Ta for Nb could significantly improve the piezoelectricity of alkali niobate system. 11,12 The higher electronegativities of Ta compared to Nb were expected to make the alkaline niobate-based perovskite more covalent, which would benefit the improvement in piezoelectricity.…”

“…The development of lead‐free piezoelectric materials has attracted much attention recently due to the toxicity of Pb 1‐5 . Owing to the large piezoelectric coefficient and the excellent composition tunable property, the alkali niobate system, such as (K, Na)NbO 3 , KNbO 3 , etc., has been considered as the most promising lead‐free candidate 6‐10 . Saito et al and Wu et al have demonstrated that partial substitution of Ta for Nb could significantly improve the piezoelectricity of alkali niobate system 11,12 .…”

Insights into the Correlation between Tetragonal Phase and Temperature Stability of Potassium Sodium Niobate Based Ceramics from Domain Behaviors

“…However, differences were observed in their descending behaviors. The R–O–T sample showed much lower small signal d 33 temperature stability compared with T and O–T samples, which may be donated by its low T C of 238 °C, [ 50 ] as listed in Figure S5 in the Supporting Information. Through the comparative analysis between small signal d 33 temperature stability and unipolar strain temperature stability, contrary to the benign unipolar strain stability, the R–O–T sample exhibited the worst small signal d 33 temperature stability.…”

New Type of Thermoelectric CdSSe Nanowire Chip

“…A key solution to reduce the consumption of fossil fuels is to harvest this waste energy because 500 million tons of standard coal could be saved, which will reduce 1.31 billion tons of CO 2 emissions. The thermoelectric effect that makes a direct conversion between thermal and electrical energy, possesses a high potential in the waste heat harvesting field, exhibiting excellent characteristics including good stability, no pollution, high repeatability, low cost, compared to solar cells, wind nanogenerator, and piezoelectric devices. − In the thermal–electrical field, a key parameter to evaluate the conversion efficiency is the unitless figure of merit ( ZT ), see eq where S , σ, T , and k are the Seebeck coefficient (V/K), the electric conductivity (S/m), the current absolute temperature of the material (K), and the thermal conductivity (W/m·K), respectively. It demonstrates that improving the performance of a thermoelectric generator need to increase electric conductivity, Seebeck coefficient, and decrease thermal conductivity.…”