Significantly enhanced dc electrical resistivity and piezoelectric properties of Tb‐modified CaBi2Nb2O9 ceramics for high‐temperature piezoelectric applications

Abstract

AbstractBismuth layer–structured ferroelectric calcium bismuth niobate (CaBi2Nb2O9, CBN) is considered to be one of the most potential high‐temperature piezoelectric materials due to its high Curie temperature Tc of ∼940°C, but the drawbacks of low electrical resistivity at elevated temperature and low piezoelectric performance limit its applications as key electronic components at high temperature (HT). Herein, we report significantly enhanced dc electrical resistivity and piezoelectric properties of CBN ceramics through rare‐earth element Tb ions compositional adjustment. The nominal compositions of Ca1−xTbxBi2Nb2O9 (abbreviated as CBN‐100xTb) have been fabricated by conventional solid‐state reaction method. The composition of CBN‐3Tb exhibits a significantly enhanced dc electrical resistivity of 1.97 × 106 Ω cm at 600°C, which is larger by two orders of magnitude compared with unmodified CBN. The donor substitutions of Tb3+ ions for Ca2+ ions reduce the oxygen vacancy concentrations and increase the band‐gap energy, which is responsible for the enhancement of dc electric resistivity. The temperature‐dependent dc conduction properties reveal that the conduction is dominated by the thermally activated oxygen vacancies in the low‐temperature region (200–350°C) and by the intrinsic conduction in the HT region (350–650°C). The CBN‐3Tb also exhibits enhanced piezoelectric properties with a high piezoelectric coefficient d33 of ∼13.2 pC/N and a high Tc of ∼966°C. Moreover, the CBN‐3Tb exhibits good thermal stabilities of piezoelectric properties, remaining 97% of its room temperature value after annealing at 900°C. These properties demonstrate the great potentials of Tb‐modified CBN for high‐temperature piezoelectric applications.