Influence of Bi-perovskites on the piezoelectric properties of (K0.5Na0.5)NbO3-based lead free ceramics

Abstract

Bi-perovskites, such as BiFeO3 (BF), BiInO3 (BI) and BiScO3 (BS), were added to (Li0.04K0.52Na0.44)(Nb0.84Ta0.1Sb0.06)O3 (LF4) to improve the piezoelectric properties of lead-free piezoelectric ceramics. The addition of Bi-perovskites up to 0.6 mol% did not depress the sinterbility of ceramics and the relative densities above 96% could be achieved by a powders-solid state reaction process. The c/a ratio of the tetragonal lattice of the LF4 ceramics was monotonously reduced with the amount of the BF added. The electrical insulation of the LF4 was improved with the addition BF, making the poling procedure under high electric fields become easy. The addition of BF was also effective to enhance the remnant polarization of the LF4 and the piezoelectric d33 constant of 358 pm/V was obtained by the addition of 0.4 mol% BiFeO3. However, the enhancement of the remnant polarization was not observed when the BI and BS were added to the LF4.

Fabrication of Lead-Free (Na0.52K0.44Li0.04)(Nb0.84Ta0.10Sb0.06)O3Piezoelectric Ceramics by a Modified Solid-State Reaction Method

“…These peaks are attributed to the tetragonal and/or orthorhombic perovskite structure without any secondary phases. [4][5][6]13) A remarkable difference between LF4-500-Air and LF4-500-O 2 ceramics is observed in the peaks near 45 . The LF4-500-Air shows the orthorhombic phase and the LF4-500-O 2 has mixed structure of the orthorhombic and tetragonal phases.…”

“…It is known that the defect sites (A site defect of ABO 3 perovskite and oxygen defect) are formed under sintering. 5,6,13) In this study, we prepared the perovskite LF4 powder at the low temperatures. When the LF4 with the perovskite structure is sintered, the decomposition of the perovskite and the volatilization of Li, Na, and K hardly occur.…”

“…Additionally, it is reported that doping a atom with different charge makes the dielectric peak associated with the ferroelectric to paraelectric transition broadened and changes the T c value. 13,14) This is because the formed oxygen defects and the presence of the atoms with different charge cause the diffused phase transition and changes the T c value. In the elements in LF4, Sb is most easy to be reduced.…”

Shear-Mode Industrial Inkjet Head Using Lead-Free Piezoelectric Ceramics

“…By such a background, there are many research reports about lead-free piezoelectric materials. [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34] (Li,Na,K)NbO 3 -based ceramics such as Li 0:06 (Na 0:5 K 0:5 ) 0:94 NbO 3 ceramic have been focused owing to their high piezoelectric properties, a high coercive field and a high Curie temperature. 35,36) For further improvement of the piezoelectric properties of these materials, the method of creating fine powder and control technology for domain structures have been studied.…”

Miniature Ultrasonic Motor Using Shear Mode of Potassium Sodium Niobate-Based Lead-Free Piezoelectric Ceramics

“…By substituting K and Na with Li, and/or Ta, Sb with Nb, fully densified KNN ceramics could be obtained under atmospheric pressure and the piezoelectric and electromechanical properties were enhanced near the phase transition boundary formed with substitutions. [9][10][11][12] The properties were further enhanced with the substitution of BiFeO 3 (BF) because of the strong ferroelectric nature of BF, 13) and the temperature dependence was improved with SrTiO 3 substitution. 14) All of these researches focused on the increases in the piezoelectric coefficients d and k, indicating a ''soft-type''.…”