Remarkably High‐Temperature Stability of Bi(Fe_1−xAl_x)O₃–BaTiO₃ Solid Solution with Near‐Zero Temperature Coefficient of Piezoelectric Properties

Abstract

The 0.72Bi(Fe1−xAlx)O3–0.28BaTiO3 (x = 0, 0.01, 0.03, 0.05, and 0.07, abbreviated as BFAx–BT) lead‐free high‐temperature ceramics were prepared by the conventional ceramic processing. Systematic investigation on the microstructures, crystalline structures, dielectric and piezoelectric properties, and high‐temperature stability of piezoelectric properties was carried out. The crystalline structures of BFAx–BT ceramics evolve from rhombohedral structure with x < 0.01 to the coexistence of rhombohedral structure and pseudocubic phases with x ≈ 0.01, finally to pseudocubic phases when x > 0.03. Remarkably high‐temperature stability with near‐zero temperature coefficient of piezoelectric properties (TCkp), together with improved piezoelectric properties has been achieved for x = 0.01 BFAx–BT ceramics. The BFAx–BT(x = 0.01) ceramics simultaneously show the excellent piezoelectric properties of d33 = 151 pC/N, kp = 0.31 and super‐high‐temperature stability of Td = 420°C, TCkp = 1 × 10−4. It is considered that the observed strong piezoelectricity and remarkably high‐temperature stability should be ascribed to the phase coexistence of rhombohedral and pseudocubic phases. The rhombohedral phases have a positive TCkp value and the pseudocubic phases possess a negative TCkp value. Thus, the TCkp value of BFAx–BT ceramics can be tuned by composition of x.

Enhanced insulating and piezoelectric properties of BiFeO3‐BaTiO3‐Bi0.5Na0.5TiO3 ceramics with high Curie temperature

“…Figure A and B exhibit the temperature‐dependent the dielectric loss ( tanδ ) and relative permittivity ( ε r ) of BF‐BT‐ x BNT ceramics measured at 10 kHz. As increasing test temperature, the tanδ of all samples firstly reduces, and then increases (Figure A), which may be attributed to incremental conductivity at high temperature . The addition of BNT leads to reduced tanδ in the temperature range of 100‐550°C.…”

“…As increasing x , the amount of impurities increases (Figure A2). The calcined BF‐BT powder has a single (111) peak, indicating a main single‐ PC phase . After adding BNT, the calcined powders at 0.01 ≤ x ≤ 0.07 have a split (111) peak with R peak, indicating the formation of R phase.…”

Structure, Ferroelectric, Piezoelectric, and Ferromagnetic Properties of BiFeO3‐BaTiO3‐Bi0.5Na0.5TiO3 Lead‐Free Multiferroic Ceramics

“…As a result, the high resistivity of the ceramics sintered at 1000°C for 2 h is obtained. 15 From Fig. 40,41 Figures 5(a-c) show the temperature dependences of the relative permittivity e r and dielectric loss tand at 1 MHz for the poled BFO-BT-BNT-x ceramics sintered at 1000°C for 2 h and the variation in T m of the BFO-BT-BNT-x ceramics with x, respectively.…”

“…[3][4][5] However, pure BiFeO 3 ceramic exhibits poor electric insulation because of the reduction of Fe 3+ to Fe 2+ during sintering. ), 6,9,10 partial substitutions of analogous ions for Bi 3+ and Fe 3+ in the BiFeO 3 lattices (e.g., La 3+ , Sm 3+ , and Gd 3+ for Bi 3+ or Ga 3+ , Al 3+ and Co 3+ for Fe 3+ ), [11][12][13][14][15][16] and the formation of solid solutions of BiFeO 3 with other ABO 3 -type perovskites (e.g., CaTiO 3 , BaTiO 3 , SrTiO 3 , NaNbO 3 , and Bi 0.5 K 0.5 TiO 3 , etc.). [5][6][7] Moreover, BiFeO 3 with a pure perovskite structure is very difficult to synthesize in which some impurity phases (e.g., Bi 2 Fe 4 O 9 , Bi 25 FeO 40 , etc.)…”

Temperature stability of sodium-doped BiFeO3–BaTiO3 piezoelectric ceramics

“…binary systems have been developed as candidates with superior properties to replace leadbased ceramics [13][14][15][16][17]. Among those available systems, (1 -x) BiFeO 3 -xBaTiO 3 (abbreviated as BF-BT) is regarded as one of the most promising systems due to the high Curie temperature and excellent piezoelectric properties [17][18][19][20][21].…”