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The incorporation of rare-earth elements into BaTiO 3 -based multilayer ceramic capacitors (MLCCs) plays a pivotal role in enhancing the dielectric constant and reliability. In this study, The BaTiO 3 -based ceramics doped with La and Dy were prepared separately and their dielectric properties and reliability were thoroughly compared. The La-doped sample exhibited a significantly enhanced dielectric constant, which can be attributed to the short-range migration of liberated oxygen vacancies (V O • • ) facilitated by the incorporation of defects [ L a B a • ‐ M g T i ″ - L a B a • ]. However, the presence of free V O • • in the La-doped sample led to a significant reduction in insulation resistivity during the initial application of the electric field. Microstructural analysis of the failure points resulted in the proposal of an electrical breakdown model, which elucidates the superior breakdown strength observed in the La-doped sample. This study provides novel insights for the development of MLCCs with high dielectric constants and high reliability. [ABSTRACT FROM AUTHOR]

CaBi 2 Nb 2 O 9 (CBN) with the Aurivillius phase has a high Curie temperature (T C) and remarkable fatigue resistance, which has great potential for application as high-temperature sensors. However, due to its low piezoelectric properties, its practical application remains a great challenge. In this paper, Ca 1- x Ce x Bi 2 Nb 2 O 9 ceramics were prepared by the direct reaction sintering (DRS) and conventional preparation (CP) methods, respectively. The experimental results indicate that Ce doping can increase the piezoelectric coefficient d 33 of CBN ceramics by about two times. Among them, the grain size of the samples prepared by the DRS method is finer and more uniform, and the d 33 value of DRS samples is about 3.6–9.4 % higher than that of CP samples. The DRS sample Ca 0·97 Ce 0·03 Bi 2 Nb 2 O 9 has a d 33 value of 18.9 pC/N, a T C of 948 °C, and a resistivity of 1.1 × 105 Ω cm at 600 °C. This study shows that DRS method is an effective densification method, which can prepare CBN-based ceramics with excellent comprehensive properties, and provides an innovative preparation route to explore CBN-based ceramics with excellent piezoelectric properties. [ABSTRACT FROM AUTHOR]

Lead-free piezoelectric ceramics of the [0.852(Bi 0.5-x Sr x Na 0.5)-0.11(Bi 0.5 K 0.5)-0.038Ba]Ti (1-x) Ta x O 3 (designated as BNKT-BT-xTaSr) ternary system were prepared with co-doping of Ta5+ and Sr2+. The purpose of this study is to investigate the effects of co-doping of Ta and Sr element on the microstructure, phase structure electrical properties, and electrostrain behavior of BNKT-BT-xTaSr ceramics. With the increase of Ta5+ and Sr2+ doping, the transition temperature (T F-R) of the modified doped BNKT-BT-xTaSr ceramics from ferroelectric to relaxed phase decreases to below room temperature (RT). When x = 0.005, the BNKT-BT-xTaSr ceramics reached a large electrostrain of 0.46%(d * 33 = 657 p.m./V) at RT under an electric field of 7 kV/mm, which is caused by the transition from ergodic relaxor phase to ferroelectric phase under a high applied electrical field. In addition, the electrostrain is increased to 0.48% (d * 33 = 685 p.m./V) under the same electric field after the thermal aging process at 80 °C for two weeks. This study demonstrates that the A/B site co-doping could effectively improve the electrostrain properties of BNKT-BT-xTaSr ferroelectric ceramics. [ABSTRACT FROM AUTHOR]

CaBi 2 Nb 2 O 9 (CBN) is a bismuth layered ferroelectric material with extremely high Curie temperature and low dielectric loss, which has great application potential in ultra-high temperature field. However, because of its low piezoelectric coefficient, its practical application still faces great challenges. This study successfully prepared Ca 1-x Ce x Bi 2 Nb 1.98 (W 2/3 Mn 1/3) 0.02 O 9 (x = 0–0.05) two-layer ferroelectric ceramics using direct-reaction sintering method. A pseudo tetragonal structure was successfully constructed near x = 0.02 using the substitution method of Ce4+ at site A, and W6+ and Mn4+ at site B, which altered the crystal structure of CBN based ceramics. The properties of CBN-based piezoelectric ceramics have been significantly improved by this modification. It has a higher piezoelectric constant (d 33 = 20.6 pC/N) and Curie temperature (T c = 950 °C), while having a lower dielectric loss (tan δ = 0.031 at 500 °C). In addition, CaBi 2 Nb 2 O 9 based piezoelectric ceramics also show excellent thermal stability. After annealing at 900 °C for 2 h, the d 33 value remained high at 19.2 pC/N, retaining about 93.2% of its original value. Therefore, these findings indicate that Ca 1-x Ce x Bi 2 Nb 1.98 (W 2/3 Mn 1/3) 0.02 O 9 is a high-temperature piezoelectric material with great potential. [ABSTRACT FROM AUTHOR]

• A novel method for designing an eco-friendly UHPC is presented. • A DOD model for multi-object optimization of UHPC is built. • A new UHPC efficiently incorporating steel slag is developed. • The newly developed UHPC exhibits admirable ecological value. This paper addresses an innovative method for the development of eco-friendly ultra-high performance concrete (UHPC), towards efficient steel slag application and synergetic optimization of multi-objective. Specifically, a D-optimal design (DOD) based regression model for property prediction with high goodness of fit (R2 > 0.9) is established. Then, a new UHPC is designed by a numerical optimization method based on the established DOD model. Furthermore, to verify the merit of the designed UHPC, some important properties of the UHPC samples are evaluated. The obtained results reveal that the addition of steel slag powder (SSP) contributes to the improvement of UHPC workability, and the highest slump flow is 268 mm. In addition, the increase of SSP content is detrimental to the early compressive strength, but does not affect the later strength of UHPC (130 ± 2 MPa). Besides, the chloride penetration resistance of UHPC will decrease with the incorporation of SSP, but its anti-chloride permeability is still lower than ordinary concrete. Conclusively, it is demonstrated that the use of this statistical design method could not only benefit environmental protection but also produce a new green UHPC with excellent properties. [ABSTRACT FROM AUTHOR]