Enhancement of Electromechanical and Piezoelectric Charge Coefficient in Lead-Free Na_0.2K_0.3Bi_0.5TiO₃ Ceramic through Poling Effect

In device applications like transportable gas ignitors, lighters, and energy storage, ferroelectric materials play a crucial role. When K<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1+</sup> is substituted into NBT ceramics (Na<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.2</inf>K<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.3</inf>Bi<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.5</inf>TiO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> or NKBT-30), the Effect of K<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1+</sup> on dielectric, electric field reliant (the poling field (E<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">P</inf>) from 10 to 52 kV/cm) piezoelectric coefficient (d<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">33</inf>), electromechanical coupling constant (k<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p</inf>), properties were thoroughly investigated. The microstructural analysis highlighted that an optimal grain size distribution and phase purity are crucial for achieving superior piezoelectric performance. Our findings also revealed optimized poling parameters at E<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">P</inf> = 52 kV/cm, yielding an elevated piezoelectric coefficient of 100 pC/N and the electromechanical coupling factors of 0.43 (k<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p</inf>) in NKBT with a high dielectric constant of ≈ 4000, a dielectric loss (tanδ) of 0.0299 in 100 kHz frequency. The impact of electric poling on the piezoelectric characteristics of Na<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.2</inf>K<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.3</inf>Bi<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.5</inf>TiO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> has been investigated across varying poling field strengths.