Effect of the sintering technique on the ferroelectric and d33 piezoelectric coefficients of Bi0.5(Na0.84K0.16)0.5TiO3 ceramic

Abstract

In the search of lead-free piezoelectric materials, ceramic processing techniques offer potential tools to increase the piezoelectric and ferroelectric properties in addition to new chemical compositions. Powders of pure BNKT16 (Bi 0.5 (Na 0.84 K 0.16 ) 0.5 TiO 3 ) phase were synthesized by sol-gel method with a low crystallization temperature (750 ℃ ). Ceramic samples were sintered by pressureless sintering (PLS), sinter-forging (SF), and spark plasma sintering (SPS) techniques. Structural, morphological, and chemical characterizations were performed by XRD, Raman, EDS, and SEM. Sintered samples by PLS and SF exhibit rod-like grains associated to bismuth volatility. The highest remanent polarization (11.05 µC/cm 2 ), coercive field (26.2 kV/mm), and piezoelectric coefficient (165 pC/N) were obtained for SF sample. The piezoresponse force microscopy (PFM) analysis shows that the crystallites at the nanoscale exhibit piezoelectric phenomenon and the highest piezoelectric response is reported for PLS sample. The presence of the rhombohedral phase, the increase in grain and crystallite size, and the oriented rod-like inclusions favoring the crystallographic texture are facts that enhance the piezoelectric coefficient for BNKT16 piezoceramics.

The effectiveness of published continuum constitutive laws to predict stress‐assisted densification of powder compacts

“…Table 3 shows the parameters for Equations (23) and (24). The SOVS model density dependence is fitted to the Scherer model density curve by adjusting the reference viscosity to 𝜂 0 = 3.78 × 10 −13 Pa∕s and the activation energy 𝑄 = 250 kJ∕mol following Equation (18). The difference in the numerical values for the reference viscosity and the activation energy between the "S" and "SOVS" models is a result of the differences in how viscosity has been introduced in the two models.…”

Electrocaloric Effect of Structural Configurated Ferroelectric Polymer Nanocomposites for Solid-State Refrigeration

“…Among all of the EC materials, a ferroelectric nanocomposite is one of the most promising electrocaloric refrigeration materials, which is an alternative to replace the traditional refrigerator and the air conditioner compressor due to its good adiabatic temperature changes (Δ T ), isothermal entropy (Δ S ), and significantly improved efficiency of thermal cooling . In addition, ferroelectric materials play a vital role in enhancing the performance of composite materials. − To complete the design of high-performance electrocaloric devices for advanced flexible cooling systems, it is crucial to comprehensively consider the optimization of composite materials, structural design of the nanocomposite, and device integration. A giant ECE requires a large entropy change correlated with the polarization change.…”

Correlation between the structure and dielectric constant of Bi0.5(Na1‐xLix)0.5TiO3 (0 ≤ x ≤ 0.20) solid solutions

“…Several studies have been reported in the literature on the modifications of the composition of BNT to overcome the drawbacks and to improve its piezoelectric properties 5–10 . Most of these studies are centered on the substitution of Na + by K + in Bi 0.5 (Na 1‐ x K x ) 0.5 TiO 3 , and these compositions are considered as potential candidates for various piezoelectric applications 11–23 . Sasaki et al studied the structural, dielectric, and piezoelectric properties of Bi 0.5 (Na 1‐ x K x ) 0.5 TiO 3 solid solution series and found the morphotropic phase boundary (MPB) region in the range x = 0.16‐0.20 and the piezoelectric properties are maximum in this compositional range 18 .…”

“…[5][6][7][8][9][10] Most of these studies are centered on the substitution of Na + by K + in Bi 0.5 (Na 1x K x ) 0.5 TiO 3 , and these compositions are considered as potential candidates for various piezoelectric applications. [11][12][13][14][15][16][17][18][19][20][21][22][23] Sasaki et al studied the structural, dielectric, and piezoelectric properties of Bi 0.5 (Na 1-x K x ) 0.5 TiO 3 solid solution series and found the morphotropic phase boundary (MPB) region in the range x = 0.16-0.20 and the piezoelectric properties are maximum in this compositional range. 18 Many other studies have also reported on the enhanced piezoelectric and dielectric performances of Bi 0.5 (Na 1-x K x ) 0.5 TiO 3 in the MPB region.…”