Enhanced electrical properties of Cr₂O₃ addition NBT‐based high‐temperature piezoelectric ceramics

Abstract

Owing to industrial and technological developments, there has been an increasing demand for piezoelectric ceramics that can function at temperatures of 500°C or higher. Na0.5Bi4.5Ti4O15 (NBT) with its high Curie temperature (TC) of 650°C is a typical bismuth layer–structured ferroelectric. However, its relatively low piezoelectric coefficient (d33 ∼ 16 pC/N) hinders its potential application at high temperatures. In this study, compositions of Ca0.05(Na0.5Bi0.5)0.95Bi4Ti4O15 with different additions of Cr2O3 (CNBT–Cr100x) were designed based on previous studies on Ca2+‐doped NBT piezoceramics, and the effects of the addition on the structural and electrical properties were investigated. The d33 value of CNBT–Cr20 was as high as 29 pC/N, almost twice higher than that of pure NBT ceramics. This increase was investigated in depth using X‐ray diffraction refinement and piezoelectric force microscopy in terms of intrinsic and extrinsic contributions. The Ps values of CNBT and CNBT–Cr20 were almost equal. The density of the domain walls of CNBT–Cr20 was significantly higher than that of CNBT, indicating that the increase of d33 of CNBT–Cr20 is mainly due to the increase in the extrinsic contribution. The CNBT–Cr20 ceramic exhibited excellent properties with a high TC of 655°C, a high d33 of 29 pC/N, and a resistivity high than 106 Ω cm at 500°C, demonstrating its potential for applications at high temperatures such as 500°C.

High‐performance bismuth titanate‐ferrite (Bi5Ti3FeO15) for high‐temperature piezoelectric applications

“…The degree of structural distortion Δ is defined as follows: 33 $$$$\begin{equation}\Delta \ = \frac{{\mathrm{1}}}{Z}\ \sum \left( {\frac{{R{\mathrm{ - }}\bar{R}}}{{\bar{R}}}} \right)\end{equation}$$$$where Z is the coordination number, R is the individual bond length, and R̅ is the average bond length. As listed in Table 2, the Δ value increases with increasing tungsten substitution, demonstrating that despite the slight decrease in the tilting degree, the rotation distortion has a dominant effect on increasing the degree of lattice distortion, which plays a positive role in enhancing the piezoelectric properties as an intrinsic contribution 34 …”

“…As listed in Table 2, the Δ value increases with increasing tungsten substitution, demonstrating that despite the slight decrease in the tilting degree, the rotation distortion has a dominant effect on increasing the degree of lattice distortion, which plays a positive role in enhancing the piezoelectric properties as an intrinsic contribution. 34 Figure 3 shows the SEM images and energy-dispersive X-ray spectroscopy (EDS) mapping of the natural surfaces of BTF-100xW. As indicated, all samples are dense without obvious pores, suggesting that the fabrication and sintering processes are appropriate.…”

Decoding intrinsic and extrinsic contributions for high piezoelectricity of CBT-based piezoelectric ceramics

“…In addition, the low resistivity and temperature stability of BLSFs are still obstacles for their practical applications in higher temperature ranges. 8 Among BLSFs, the CaBi 4 Ti 4 O 15 (CBT, m = 4) ceramic is one of many good candidates for high temperature piezoelectric sensors due to its good electrical properties at high temperatures. 9,10 Compared with other BLSFs, such as CaBi 2 Nb 2 O 9 ( d 33 = 6 pC/N and T C =943 °C), Bi 4 Ti 4 O 12 ( d 33 = 8.0 pC/N and T C = 675 °C), and CaBi 4 Ti 4 O 15 ( d 33 = 9 pC/N and T C = 790 °C), the ceramic system often exhibits good comprehensive properties at 450 °C–550 °C.…”

Li0.5Bi2.5Nb2O9: An alkali‐metal bismuth layer structured ferroelectric with high TC and small orthorhombic distortion

“…Alkali‐metal BLSFs are an important family of Aurivillius‐type high‐temperature piezoelectrics 12,19–21 . Among currently reported alkali‐metal BLSFs, two‐layer structured Na 0.5 Bi 2.5 Nb 2 O 9 (NBN) shows the highest Curie temperature (∼790°C) and has been widely investigated 22–25 .…”

“…Alkali-metal BLSFs are an important family of Aurivillius-type high-temperature piezoelectrics. 12,[19][20][21] Among currently reported alkali-metal BLSFs, twolayer structured Na 0.5 Bi 2.5 Nb 2 O 9 (NBN) shows the highest Curie temperature (∼790 • C) and has been widely investigated. [22][23][24][25] The cell parameters of NBN are a ∼ 5.4937 Å, b ∼ 5.4571 Å, c ∼ 24.9169 Å, so the orthorhombic distortion a/b of NBN is 1.0067.…”