Microstructure–Property Relationships in Liquid Phase‐Sintered High‐Temperature Bismuth Scandium Oxide‐Lead Titanate Piezoceramics

Abstract

High‐temperature piezoelectrics are necessary for aeronautic and aerospace applications. The principal challenge for the insertion of piezoelectric materials is their limitation for upper use temperature, which is due to low Curie temperature and increasing conductivity at high temperatures. We investigated processing, microstructure, and property relationships of (1−x)BiScO3−(x)PbTiO3 composition as a promising high‐temperature piezoelectric. The effects of excess PbO and Bi2O3 and their partitioning in grain boundaries were studied using impedance spectroscopy, ferroelectric, and piezoelectric measurement techniques. Excess Pb addition increased the grain‐boundary conduction and the grain‐boundary area resulting in ceramics with higher AC‐conductivity (tan δ=0.9 and 1.7 for 0 and 5 at.% excess Pb at 350°C and at 10 kHz) that were not resistive enough to pole. Excess Bi addition increased the resistivity (tan δ=0.9 and 0.1 for 0 and 5 at.% excess Pb at 350°C and at 10 kHz), improved poling, and increased the piezoelectric coefficient from 354 to 408 pC/N for 5 at.% excess Bi addition. Thus, excess Bi2O3 proved to be a successful liquid phase forming additive to improve the 0.37BiScO3–0.63PbTiO3 piezoceramics for high‐temperature applications, as a result of increased resistivity and enhanced piezoelectric activity.

Structure and electrical behaviors of 0.36BiScO3–0.64PbTiO3 ceramics with overdosing Bi and Pb starting materials

“…At the saturation state of the polarization (Fig. 4a), the P r and E c of the BS-PT-II ceramic sintered at 1000 C for 2 h are 43.2 mC/cm 2 and 30.9 kV/cm, respectively, higher than the previously reported values [5][6][7][8][9]15,16,26,27,30]. The switching current-electric field curve exhibits two slightly asymmetric peaks with peaks value 10 and À12 A/m 2 , respectively.…”

“…The strain behavior results indicate a bipolar strain of 0.4% and a unipolar strain of 0.23% (Fig. 4b and c), respectively, both again higher than previously reported values [5][6][7][8]15,26,27,30].…”

“…To address this problem, Zou et al prepared fine BS-PT powder by a sol-gel method followed by a two step sintering ceramic route [25]. Sehirlioglu et al later developed a liquid phase sintering technique and concluded that excess Bi 2 O 3 is a successful liquid phase forming additive and improves the resultant BS-PT ceramics for high temperature applications [26,27]. A more conventionally used technique is by sintering the ceramics in a Bi/Pb rich atmosphere.…”

BiFeO3–PbZrO3–PbTiO3 ternary system for high Curie temperature piezoceramics

“…Sehirlioglu et al reported previously that excess Bi 2 O 3 would enhance the resistivity and ferroelectric properties in BiScO 3 -PbTiO 3 . 21 It is speculated that the Bi-rich Bi 46 Fe 2 O 72 impurity phase formed under lower sintering temperatures is also critical to good ferroelectric properties in the BF-PZ-PT ternary solid solution system.…”

Effects of sintering atmosphere on microstructure and electrical properties of BiScO3–PbTiO3 high-temperature piezoceramics

“…It was found that the resisitivity of samples sintered in air is higher than that of those sintered in sacrificial powders throughout the whole temperature range studied. The lower resistivity of sample sintered in sacrificial powders may be attributed to the second-phase at grain-boundary which would cause the decrease in resistance [20]. The resistivity of both samples sintered in air is more than 10 9 cm at 400 • C. The temperature dependence of conductivity was fitted according to the Arrhenius equation:…”