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<p>Rare earth (RE = Er<sup>3</sup>⁺, Y<sup>3</sup>⁺, Gd<sup>3</sup>⁺)-substituted lead-free piezoceramics, with the composition [(Ba<sub>0.85</sub>Ca<sub>0.15</sub>)0.99RE<sub>0.01</sub>][(Zr<sub>0.1</sub>Ti<sub>0.9</sub>)O<sub>3</sub>], were successfully synthesized by solid-state reaction method. Structural analysis confirmed the coexistence of orthorhombic (<i>Amm2</i>) and tetragonal (<i>P4mm</i>) crystal lattice symmetries near room temperature, along with a dense microstructure (relative density &gt; 95%). Temperature-dependent dielectric measurement shows the presence of polymorphic phase transitions, i.e., <i>T</i><sub>O-T</sub> and <i>T</i><sub>T-C</sub>. All compositions exhibited typical ferroelectric behavior, as evidenced by polarization–electric field hysteresis loops. Complex impedance spectroscopy analysis reveals that both grain and grain boundary contribution are responsible for the electrical conduction of the ceramics, with grain boundaries exhibiting higher resistance (<i>R</i><sub>gb</sub> &gt; <i>R</i><sub>b</sub>). The Nyquist plot analysis showed a negative temperature coefficient of resistance (NTCR), signifying semiconducting behavior that is also evidenced by a increase of DC electrical conductivity with temperature. A non-Debye-type relaxation process was observed, where the relaxation time decreased with increasing temperature, obeying the Arrhenius relationship, similar to DC conductivity. The calculated activation energies for both relaxation and conduction were comparable, suggesting identical charge carriers. Specifically, the relaxation mechanism was attributed to single-ionized oxygen vacancies in the grain region and double-ionized oxygen vacancies in the grain boundary region. These findings highlight the potential of these lead-free ceramics for high-temperature electronic devices with NTCR characteristics.</p>

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Impact of rare earth Er3⁺, Y3⁺, Gd3⁺ substituents on electrical properties of BaTiO3-CaTiO3-BaZrO3 lead-free electroceramics with an emphasis on complex impedance spectroscopy

  • 期刊论文

  • 发表日期：

    2025年7月23日

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  • Nikita J. Kapadi,
  • Tejas K. Jadhav,
  • Rahul C. Kambale

摘要

Rare earth (RE = Er3⁺, Y3⁺, Gd3⁺)-substituted lead-free piezoceramics, with the composition [(Ba0.85Ca0.15)0.99RE0.01][(Zr0.1Ti0.9)O3], were successfully synthesized by solid-state reaction method. Structural analysis confirmed the coexistence of orthorhombic (Amm2) and tetragonal (P4mm) crystal lattice symmetries near room temperature, along with a dense microstructure (relative density > 95%). Temperature-dependent dielectric measurement shows the presence of polymorphic phase transitions, i.e., TO-T and TT-C. All compositions exhibited typical ferroelectric behavior, as evidenced by polarization–electric field hysteresis loops. Complex impedance spectroscopy analysis reveals that both grain and grain boundary contribution are responsible for the electrical conduction of the ceramics, with grain boundaries exhibiting higher resistance (Rgb > Rb). The Nyquist plot analysis showed a negative temperature coefficient of resistance (NTCR), signifying semiconducting behavior that is also evidenced by a increase of DC electrical conductivity with temperature. A non-Debye-type relaxation process was observed, where the relaxation time decreased with increasing temperature, obeying the Arrhenius relationship, similar to DC conductivity. The calculated activation energies for both relaxation and conduction were comparable, suggesting identical charge carriers. Specifically, the relaxation mechanism was attributed to single-ionized oxygen vacancies in the grain region and double-ionized oxygen vacancies in the grain boundary region. These findings highlight the potential of these lead-free ceramics for high-temperature electronic devices with NTCR characteristics.