The Effects of Na/K Ratio on the Electrical Properties of Sodium‐Potassium Bismuth Titanate Na_0.5Bi_4.5Ti₄O₁₅–K_0.5Bi_4.5Ti₄O₁₅

Abstract

The bismuth layer‐structured ferroelectrics (BLSFs) sodium‐potassium bismuth titanate (NaxK1 − x)0.5Bi4.5Ti4O15 polycrystalline ceramics with cobalt substitution were synthesized using conventional solid‐state processing. The phase structure, microstructural morphology, and electrical properties of NKBT ceramics with different Na/K ratio were investigated in detail. The substitutions of Na for K in NKBT ceramics cause the decrease in unit cell volume, resulting in the diffraction peaks shift to higher angles. The piezoelectric activities, electromechanical properties, and remnant polarization were found to be enhanced with the increasing ratio of Na/K. The Curie temperature Tc of NKBT piezoelectric ceramics was found to linearly increase from 578°C to 670°C with the increasing ratio of Na/K, which is ascribed to the small ionic radius of Na+ ions in comparison with K+ ions. The large piezoelectric activities and high electromechanical properties, together with high Curie temperature, make NKBT ceramics promising for high‐temperature piezoelectric applications.

Diffusion-controlled alloying of single-phase multi-principal transition metal carbides with high toughness and low thermal diffusivity

“…Vickers hardness and fracture toughness results for the multi-principal compounds are shown in Fig. 4(a) [34][35][36][37][38][39][40][41][42][43] , mullite matrix composites [44][45][46][47][48][49] and refractory metal carbides and composites [52][53][54][55][56][57][58][59][60][61][62][63][64] . (b) Temperature dependence of thermal diffusivity for multi-principal carbides and metallic glasses 65,66 .…”

Comparative Study of Ferroelectric and Piezoelectric Properties of BNT-BKT-BT Ceramics near the Phase Transition Zone

“…In the BNT-BKT system, fine grained microstructures and a reduction in the coercive field from 63 to 36 kV/cm are obtained as the BKT content increases from 0 to 10 mol % [33]. The reported combination of processing parameters, specially based on the milling of mixed oxides and a solid-state reaction seeking for optimization as a function of composition, e.g., in the MPB zone, are frequently contradictory leading to the formation of spurious phases, a fine-grained microstructure, a poor density, structural defects, and thus poor ferroelectric and piezoelectric behavior.…”

Piezoelectric properties and thermal stabilities of strontium bismuth titanate (SrBi4Ti4O15)

“…Additionally, the dielectric loss tan increases sharply when the temperature is higher than 400 °C, and the low frequency dielectric loss tan is higher than high frequency loss tan, because of the increase of high temperature conduction at low frequencies. A dielectric abnormity is observed in dielectric loss tan spectra at ~450 °C, and this dielectric abnormal phenomenon has also been observed in other BLSFs, such as Bi 4 Ti 3 O 12 , Na 0.5 Bi 4.5 Ti 4 O 15 , and CaBi 2 Nb 2 O 9 systems [30][31][32], which is attributed to the oxygen vacancies during sintering process [30]. Additionally, the cerium-modified SBT ceramics show suppressed dielectric abnormity in comparison to unmodified SBT, as shown in Fig.…”