Effect of the element ratio in the doping component on the properties of 0.975(0.8Bi1/2Na1/2TiO3–0.2Bi1/2K1/2TiO3)–0.025Bix/3Mgy/3Nbz/3O3 ceramics

A new series of ternary perovskite 0.975(0.8Bi Na TiO –0.2Bi K TiO )–0.025Bi Mg Nb O (BNT–BKT–BMN, BMN‐xyz) ceramics were designed and synthesized. The effect of the element ratio in the doping component BMN on the strain, ferroelectric, piezoelectric, and dielectric properties of the BNT–BKT matrix were studied. The BMN‐430 composition without Nb element exhibits the typical features of non‐ergodic relaxor, which is characterized by a higher piezoelectric coefficient d and a butterfly‐shaped strain curve with negative strain. The introduction of trace Nb can significantly enhance the ergodicity of the system, reflecting in the high positive strain response and strain coefficient (d33∗>750pm/V) of BMN‐321 composition. In contrast, there is no significant difference in the properties between the presence and absence of Mg element. The temperature‐dependent electrical behaviors of BMN‐xyz ceramics were analyzed based on impedance spectroscopy. This study may be helpful to the design of the chemical modification strategy for the BNT‐based relaxor ferroelectrics. [Figure not available: see fulltext.] 1/2 1/2 3 1/2 1/2 3 x /3 y /3 z /3 3 3

Electro-mechano-optical properties of the Er³⁺ modified Bi_0.5Na_0.4K_0.1TiO₃ versatile ceramics

A series of Bi Er Na K TiO (BNKT-xEr) ceramics were designed and fabricated, the dopant effects on dielectric, piezoelectric and photoluminescence properties were studied. The results show that the piezoelectric property of BNKT can be enhanced by a trace amount of Er dopant, which is also reflected in the large linear electrostrain (S = 0.29%, under 55 kV/cm) achieved in BNKT-0.0025 Er. On the other hand, higher Er content can produce excellent dielectric temperature stability, with △ԑ/ԑ < ±15% over temperature range of 90∼510 °C. Meanwhile, all BNKT-xEr ceramics exhibit good photoluminescence properties, which may open new applications of these multifunctional ceramics. 0.5- x x 0.4 0.1 3 uni 150 °

Large electrostrain in Bi_1/2Na_1/2TiO₃-based relaxor ferroelectrics: A case study of Bi_1/2Na_1/2TiO₃-Bi_1/2K_1/2TiO₃-Bi(Ni_2/3Nb_1/3)O₃ ceramics

(1-x)(0.8Bi Na TiO -0.2Bi K TiO )-xBi(Ni Nb )O (BNKT-xBNN) solid solution ceramics were fabricated by high temperature solid-state reaction method. All the compositions possess relaxor ferroelectric features, among which the ergodic BNKT-0.02BNN exhibits large repeatable electrostrain value S = 0.51% at electric field of 65 kV/cm, with high piezoelectric stain coefficient d ∗ of 890 pm/V at 45 kV/cm, while the non-ergodic compositions present unrepeatable large strain response. Based on the electric field-composition phase diagram, the repeatability of strain response in ergodic compositions can be attributed to the reversible electric-field-induced phase transition. In addition, the effects of BNN contents on the macroscopic strain properties are explored by analyzing the existing states of the polar regions with corresponding thermal evolutions and electric-field-induced phase transitions. This research is expected to guide the design of lead free relaxor ferroelectric materials with desired electrostrain properties. 1/2 1/2 3 1/2 1/2 3 2/3 1/3 3 uni 3

Large strain with enhanced energy-storage and temperature stable dielectric properties in Bi_0.38Na_0.38Sr_0.24Ti_(1-x)(Mn_1/3Nb_2/3)_xO₃ ceramics

A series of novel Bi Na Sr Ti (Mn Nb ) O lead-free ceramics (BNST-100xMN) were designed and fabricated. The dielectric, ferroelectric, energy-storage, electrostrain properties, and impedance performance of these materials were systematically investigated. A large strain response under low driving electric field was obtained that benefits from the enhanced relaxor-to-ferroelectric phase transition. The optimum piezoelectric stain coefficient d * of 930 pm/V (under 40 kV/cm) was achieved in BNST-1MN composition. The substitution by MN dopant gave rise to a homogeneous micro-morphology with small grains that gave rise to an enhanced high breakdown strength (BDS). Slim and slanted ferroelectric hysteresis was obtained by introducing a larger amount of MN, and hence the BNST-2MN ceramic exhibits a high energy-storage density of 1.30 J/cm at 110 kV/cm, accompanied with an excellent fatigue-free behavior. The dielectric response exhibited a stable high temperature dielectric property with low dielectric loss. These results indicate that BNST-100xMN ceramics are promising candidates for the actuator and energy storage applications. 0.38 0.38 0.24 (1-x) 1/3 2/3 x 3 33

Optimization of Ferroelectric Ordering and Thermal Stability in Na_1/2Bi_1/2TiO₃‑Based Lead-Free Single Crystal through Defect Engineering

Environmentally friendly lead-free piezoelectric materials have been attracting significant attention in recent years. Na1/2Bi1/2TiO3-based relaxor ferroelectrics have found acceptance for application in promising lead-free transducers in high-power ultrasonic devices. However, their low thermal stability, i.e., their relatively low ferroelectric-relaxor transition temperature (TF‑R), hinders their practical application. Herein, a thermal-quenching approach is applied on a Na1/2Bi1/2TiO3 (NBT)-based single crystal, which yields a large increase in TF‑R and dramatic enhancement of its ferroelectric ordering, leading to excellent thermal stability of its dielectric, ferroelectric, and piezoelectric properties. This behavior is mainly attributed to quenching-induced domain evolution as well as its octahedral tilt, which is linked to the increased oxygen vacancies. The substitution of long-range ordered ferroelectric domains for short-range polar nanodomains contributes to its increased coherence length and, consequently, enhancement of TF‑R. This work provides an approach to the optimization of the ferroelectric ordering and thermal stability of NBT as well as an in-depth understanding of the quenching effect on the local structure, which could be applied to other relaxor-based ferroelectrics for optimization of their macroscopic properties

Optimization of Ferroelectric Ordering and Thermal Stability in Na1/2Bi1/2TiO3-Based Lead-Free Single Crystal through Defect Engineering

Environmentally friendly lead-free piezoelectric materials have been attracting significant attention in recent years. Na1/2Bi1/2TiO3-based relaxor ferroelectrics have found acceptance for application in promising lead-free transducers in high-power ultrasonic devices. However, their low thermal stability, i.e., their relatively low ferroelectric-relaxor transition temperature (TF-R), hinders their practical application. Herein, a thermal-quenching approach is applied on a Na1/2Bi1/2TiO3 (NBT)-based single crystal, which yields a large increase in TF-R and dramatic enhancement of its ferroelectric ordering, leading to excellent thermal stability of its dielectric, ferroelectric, and piezoelectric properties. This behavior is mainly attributed to quenching-induced domain evolution as well as its octahedral tilt, which is linked to the increased oxygen vacancies. The substitution of long-range ordered ferroelectric domains for short-range polar nanodomains contributes to its increased coherence length and, consequently, enhancement of TF-R. This work provides an approach to the optimization of the ferroelectric ordering and thermal stability of NBT as well as an in-depth understanding of the quenching effect on the local structure, which could be applied to other relaxor-based ferroelectrics for optimization of their macroscopic properties