Search

Electrocaloric (EC) refrigeration materials have seen significant progress recently, with efficient Barium titanate-based (BT-based) lead-free materials particularly promising for microelectronics applications. However, their performance still lags behind their lead-based counterparts, highlighting the need for further improvements. This study employs a novel density adjustment strategy (DAS) to enhance the EC performance of (0.5- x)BCT-BTZ- x BST ceramics by carefully balancing the relationships among density, dielectric breakdown strength (BDS), and Δ T. Although Δ T intuitively decreases with increasing density, enhanced BDS can partially compensate for this decrease. An excellent EC performance with Δ T of 2.21 K and Δ T /Δ E of 0.471 K mm kV−1 is obtained in x = 0.5, together with a broader temperature span of 50.3 °C near room temperature, which surpasses or is comparable to other lead-free or lead-based ones. The results suggest that the DAS provides a promising approach for developing efficient EC, making speediness of application in EC devices. [Display omitted] • Developed innovative density adjustment strategy (DAS) for (0.5- x)BCT-BTZ- x BST ceramics to reconcile ρ and Δ T relationship. • Excellent EC properties (Δ T = 2.21 K, Δ T /Δ E = 0.471 K mm kV−1, T span =50.3 ℃) achieved by balancing ρ, BDS, and Δ T. • Identified physical mechanisms responsible for enhanced EC properties. [ABSTRACT FROM AUTHOR]

• A hybrid Ag/rGO-ZnO photocatalyst settles limitations of poor photoresponse range and high charge recombination of ZnO. • The rationality of Ag/rGO-ZnO nanostructure is confirmed by PEC characterization and FDTD simulation. • Ag/rGO-ZnO shows enhanced CO 2 reduction activity and stability. [Display omitted] In this work, a plasmonic hybrid coupling-enhanced photocatalyst of Ag/rGO (reduced graphene oxide)-ZnO, integrating superior activity, lasting stability, and low cost all-in-one, is proposed to settle limitations related to narrow photoresponse range and high charge recombination on ZnO. Graphene oxide nanoflakes were successfully composited with ZnO nanorods using the self-assembly method, then modified with Ag nanoparticles. UV–vis absorption spectra, photoelectrochemical characterizations and the finite difference time domain simulations show that this nanocomposite has enhanced catalytic activity for reducing CO 2 to CO and CH 4 compared to pure ZnO (P-ZnO). By tuning the content of graphene and Ag, the maximum photocatalytic efficiency of Ag/rGO-ZnO (62.7 μmol g−1 h−1) far exceeds that of P-ZnO by at least 28 times, with high stability for more than 24 h in the absence of hole scavengers and photosensitizers. Meanwhile, with the addition of Ag and graphene, Ag/rGO-ZnO exhibits a selective tendency toward the cleaner fuel-CH 4 , which is 7 times higher than P-ZnO. Our study highlights the potential of broadening the light response range, suppressing e−/h+ recombination, and improving the stability of catalysts based on a nanocomposite structure. It also provides a more valuable reference for promoting low-cost commercial applications of ZnO photocatalysts. [ABSTRACT FROM AUTHOR]

Although KNN-based ceramics with high electric performance have been obtained by phase engineering strategy, the temperature stability is required to be the improved in the applications. Herein, a new environment-friendly 0.96K 0·4 Na 0·6 Nb 0.97- x Ta 0.03 Sb x O 3 -0.04(Bi 0.45 Sm 0.05)Na 0·5 ZrO 3 (KNNTS x -BSNZ, x = 0–0.08) ceramic system was designed, which exhibits excellent piezoelectric properties and good temperature stability. A high piezoelectric property of 510 pC/N is obtained by R-T phase engineering in the ceramics with x = 0.045. The temperature stability of electric properties is improved in the temperature range of T = 20–180 °C by Ta, Sb co-doping in KNNTS x -BSNZ ceramics with x = 0.02–0.045, benefiting from the combined effects of both the enhanced relaxor behavior and high T C. Therefore, we believe that it can broaden the application of KNN-based ceramics. • High piezoelectric coefficient (d 33 = 510 pC/N) is obtained in KNNTS x -BSNZ ceramics at x = 0.045 with R-T phase boundary. • An optimal temperature stability (S uni120°C / S uniRT = 93.1%, S uni180°C / S uniRT = 82.5%) is observed at x = 0.03. • The mechanism of enhanced temperature stability of Ta, Sb co-doped KNN-based ceramics is explained. • The physical origin for the enhanced overall electrical properties has been addressed. [ABSTRACT FROM AUTHOR]

With the increased concerns on the toxicity of lead, the barium titanate (BT) has developed a vital lead-free ferroelectric material to replace lead-based one due to the extraordinary multi-functionality. However, to date the deep understanding on evolution mechanisms of multiple electro-related performances in single BT based ceramics is still limited, and the simultaneous enhancement or balanced development of comprehensive performance in BT ceramics face challenges. Here, a new lead-free ceramic system of Ba 0.9+ x Sr 0.1- x Ti 0.91 Sn 0.09 O 3 (BSTS, 0 ≤ x ≤ 0.1) was successfully prepared by the conventional solid-state reaction method, and the dopant tuned multi-functionality and underlying physical mechanism of performance evolutions were revealed in detail. The BSTS ceramics present R-O-T-C multiphase coexistence at a wider temperature range near room temperature, along with the structural features with flattened thermodynamic energy landscape and flexible polarization rotation. Accordingly, the enhanced piezoelectric coefficient (d 33 = 600 pC/N), large electrostrictive coefficient (Q 33 = 0.0405 m4/C2, E = 30 kV/cm), superior electrocaloric effect (Δ T = 0.77 K, E = 30 kV/cm) with a wider temperature span of 49 °C (Δ T > 0.5 K), and strong electrocaloric strength (Δ T /Δ E = 0.3857 K mm/kV, E = 5 kV/cm) are simultaneously attained under smaller electric field for BSTS ceramics. It exhibits a superior comprehensive performance than many reported BT based ceramics, which is suitable for more potential applications in the emerging fields of advanced functional devices, such as high precision displacement or strain actuators and zero-global-warming-potential refrigeration with larger capacity near room temperature. This work sheds insight into simultaneously optimizing different electro-related performances, and stimulates future studies on dopant tuned multi-functionality in BT based ceramics. • A new BT based material system with R-O-T-R multiphase boundary is designed. • Enhanced d 33 , large Q 33 , and high Δ T with a wider temperature span are simultaneously achieved. • The physical origin of enhanced performance is revealed. [ABSTRACT FROM AUTHOR]

A new KNN-based lead-free piezoelectric material system of (1- x)K 0.4 Na 0.6 Nb 0.96 Sb 0.04 O 3 - x (Bi 0.45 Sm 0.05)Na 0.5 ZrO 3 (abbreviated as KNNS- x BSNZ, 0.00 ≤ x ≤ 0.06) is designed to obtain high performance to meet the requirement of next generation electronic devices. The relevant electric properties such as piezoelectricity, strain, and temperature stability are analyzed in detail. An excellent comprehensive property (d 33 ∼508 pC/N, T C ∼268 °C) is obtained in ceramic with x = 0.04 through the construction of rhombohedral-orthorhombic-tetragonal (R-O-T) phase boundary. In addition, a good temperature stability of strain for KNNS-0.04BSNZ ceramic is also obtained within the range from room temperature to 175 °C (S uni100°C / S uniRT ∼97.81%, S uni150°C / S uniRT ∼84.67%), which is comparatively superior to some reported KNN-based ceramics and lead-based ceramics. Therefore, we believe that this new material system would be a promising lead-free candidate for the practical applications. Image 1 • A new lead-free piezoelectric material system of KNNS- x BSNZ is designed. • Enhanced comprehensive performance is obtained by forming R-O-T phase boundary. • Good temperature stability of strain is achieved in the temperature range from RT to 150 °C. • The physical origin for the enhanced overall electrical properties has been addressed. [ABSTRACT FROM AUTHOR]

To obtain outstanding electrical properties of Barium titanate based ceramics to meet the requirements of the practical applications, a new system of BaZr 0.2 Ti 0.8 O 3 -(0.5- x)Ba 0.7 Ca 0.3 TiO 3 - x Ba 0.7 Sr 0.3 TiO 3 (BZT-BCT- x BST, 0 ≤ x ≤ 0.5) lead-free material was designed. A systematic study about piezoelectric, ferroelectric, and strain properties was carried out in the ceramics. The BZT-BCT- x BST ceramics with x = 0.3 exhibit an enhanced electrical property (e.g. , d 33 ∼540 pC/N, k p ∼0.42, ε r ∼4560, tan δ ∼0.023, and straiñ0.132% @30 kV/cm) as well as a good electrostrictive behavior (Q 33 ∼0.0366 m4 C−2, Straiñ0.08%), and Q 33 value is compared to PZT-baesd materials. In addition, the influence of external fields (temperature, electric field) on strain stability reveals that the strain under high driving electric fields has comparatively good temperature stability. We firmly believe that such a work can be beneficial to the practical process of BT-based ceramics. • An Enhanced comprehensive performance (e.g. , d 33 ∼540 pC/N, d 33 * ∼ 1085 p.m./V@3 kV/cm) was obtained. • A good electrostrictive behavior (Q 33 ∼0.0366 m4 C−2, Straiñ0.08%) is comparable to that of PZT-baesd materials. • The influence of external field (temperature, electric field) on strain stability has discussed. [ABSTRACT FROM AUTHOR]