Remarkably Strong Piezoelectricity of Lead‐Free (K_0.45Na_0.55)_0.98Li_0.02(Nb_0.77Ta_0.18Sb_0.05)O₃ Ceramic

Abstract

Various lead-free (K x Na 1Àx ) 0.98 Li 0.02 (Nb 0.82Ày Ta 0.18 Sb y )O 3 ceramics with x 5 0.50, y 5 0.00-0.07 or x 5 0.40-0.60, y 5 0.05 were prepared by the conventional solid-state reaction method. Systematic investigation on the microstructures, crystalline structures, and dielectric and piezoelectric properties was carried out. Remarkably strong piezoelectricity has been achieved in (K 0.45 Na 0.55 ) 0.98 Li 0.02 (Nb 0.77 Ta 0.18 Sb 0.05 )O 3 ceramic, which shows the excellent piezoelectric properties of d 33 5 413 pC/N, d 31 5 À153 pC/N, k p 5 0.50, and k 33 5 0.62. It is considered that the observed strong piezoelectricity should be ascribed to several combined decisive factors, such as the phase coexistence due to an orthorhombic-tetragonal polymorphic phase transition near room temperature, the high electronegativity of Sb 51 ions as compared with those of Nb 51 ions and Ta 51 ions, and the relatively ideal microstructure with high density, large average grain size and narrow grain-size distribution.

Microstructure, Phase Transition, and Electrical Properties of K x Na1−x NbO3 Lead-Free Piezoceramics

“…On the other hand, in recent years, modified K 0.5 Na 0.5 NbO 3 ceramics were mainly studied because the piezoelectric properties could be greatly improved by Li, Ta, and Sb doping. [11][12][13] However, such enhanced piezoelectric properties in modified KNN ceramics were proved to be attributed to the orthorhombic-tetragonal polymorphic phase transition (PPT) shifting downward to near room temperature rather than the typical MPB. 14 Therefore, these modified KNN-based ceramics were not suitable for applications in a varying-temperature environment owing to their strong temperature instability.…”

A monoclinic-tetragonal ferroelectric phase transition in lead-free (K0.5Na0.5)NbO3-x%LiNbO3 solid solution

“…[1][2][3][4][5][6][7][8][9][10][11][12] In particular, some (K,Na,Li)(Nb,-Ta,Sb)O 3 ceramics exhibit longitudinal piezoelectric coefficients of d 33 ! 400 pC=N, 1,13 which is nearly comparable with that of "soft" Pb(Zr,Ti)O 3 materials such as PZT-5A.…”

“…39 Thus, a variety of substituents (including LiNbO 3 , LiTaO 3 and LiSbO 3 ) have been added to KNN to form new KNN-based ceramics with improved relative densities and piezoelectric properties. 6,9,10,12,[40][41][42] 4,46,47 Monoclinic (M) phases are well known in Pb-based perovskites that are sandwiched between ferroelectric R and T phases near a morphotropic phase boundary (MPB). [48][49][50][51] These M phases are believed to be important to the high piezoelectricity of MPB systems, as the lower symmetry allows the polarization to rotate between pseudocubic h111i and h001i directions.…”

The preparation and the effects of K/Na ratio on the electrical properties of 0.95(Na0.96-x K x Li0.04)(Nb0.89Sb0.07Ta0.04)O3-0.05KNbO3 lead-free ceramics

“…However, shifting the T O−T down to the vicinity of room temperature is not the only way to obtain good electrical properties for KNN-base ceramics. Other factors, such as the relative density, grain orientations, grain size, grain boundaries, and domain walls, also contribute to the remarkably strong piezoelectricity [30]. Systematically investigating the dependence of piezoelectricity on these factors is significantly important from both the academic and the technological viewpoints.…”