High and Frequency‐Insensitive Converse Piezoelectric Coefficient Obtained in AgSbO₃‐Modified (Li,K,Na)(Nb,Ta)O₃ Lead‐Free Piezoceramics

Abstract

AgSbO3 was doped into KNN‐based lead‐free piezoceramics with an optimized composition of Li0.02(Na0.53K0.48)0.98Nb0.8Ta0.2O3 (abbreviated as LKNNT) to further enhance its piezoelectric property. The doping of AgSbO3 was found to be effective in reducing the grain sizes, resulting in more uniform microstructure in AgSbO3‐doped LKNNT ceramics. AgSbO3 lowers tetragonal‐orthorhombic phase transition point (TT‐O), but with a more gentle rate as compared with other dopants. A large converse piezoelectric coefficient d33* up to 598 pm/V under a relatively low electric field of 1 kV/mm was obtained in the LKNNT‐5 mol% AgSbO3 composition, whose tetragonal‐orthorhombic phase transition point (TT‐O) was controlled near room temperature, but its Curie temperature was kept at 235°C. The d33* obtained in the present material is a very high value for nontextured KNN‐based ceramics, which is attributed to the polymorphism phase transition effect and “soft” behavior caused by the addition of AgSbO3.

The phase structure and electric properties of low-temperature sintered (K, Na)NbO3-based piezoceramics modified by CuO

“…In our previous work, excellent piezoelectric performance with d 33 * ¼ 598 pm/V (E max ¼ 1 kV/mm) was obtained in 0.95Li 0.02 (Na 0.53 K 0.48 ) 0.98 Nb 0.8 Ta 0.2 O 3 -0.05AgSbO 3 (LKNNTAS) lead-free piezoceramics, which will serve as the base material in the present work [14]. On the other hand, CuO has been proved as an effective sintering aid for many kinds of piezoceramics.…”

“…[14]. Then, 0.25 wt% of CuO was added to previously synthesized LKNNTAS powders (abbreviated as LKNNTAS-CuO) by ball milling for 24 h in ethanol using ZrO 2 balls.…”

Sintering of Lead-Free Piezoelectric Sodium Potassium Niobate Ceramics

“…These modifications mostly result in a downward shift of the orthorhombic–tetragonal phase-transition temperature ( T O–T ) [19,61,62,63,64,65,66]. If the T O–T is shifted to room temperature, the piezoelectric performance can be enhanced; this is known as the polymorphic phase-transition (PPT) effect [67].…”

Further Enhancing Piezoelectric Properties by Adding MnO2 in AgSbO3‐Modified (Li,K,Na)(Nb,Ta)O3 Lead‐Free Piezoceramics

“…2,3,10,11 The piezoelectricity of KNN-based ceramics lacks temperature stability mainly because its enhancement is realized through polymorphic phase transition (PPT), which is adjusted nearly room temperature whereby two phases coexist. 2,3,7,[12][13][14][15][16][17][18][19] Certainly, the possible approach to enhance the temperature stability is shifting the PPT boundary well below ambient temperature, but it will lead to a sacrifice of piezoelectric performance. 20 Although fabricating textured samples was adopted as a solution to the dilemma, this approach is too complex for mass production.…”