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Dielectric capacitors with high energy storage performance are highly desired for next-generation advanced high/pulsed power capacitors that demand miniaturization and integration. However, the poor energy-storage density that results from the low breakdown strength, has been the major challenge for practical applications of dielectric capacitors. Herein, we propose a heterovalent-doping-enabled atom-displacement fluctuation strategy for the design of low-atom-displacements regions in the antiferroelectric matrix to achieve the increase in breakdown strength and enhancement of the energy-storage density for AgNbO 3 -based multilayer capacitors. An ultrahigh breakdown strength ~1450 kV·cm −1 is realized in the Sm 0.05 Ag 0.85 Nb 0.7 Ta 0.3 O 3 multilayer capacitors, especially with an ultrahigh U rec ~14 J·cm −3 , excellent η ~ 85% and P D,max ~ 102.84 MW·cm −3 , manifesting a breakthrough in the comprehensive energy storage performance for lead-free antiferroelectric capacitors. This work offers a good paradigm for improving the energy storage properties of antiferroelectric multilayer capacitors to meet the demanding requirements of advanced energy storage applications. AgNbO 3 has a potential for high power capacitors due to its antiferroelectric characteristics. Here, the authors achieve multilayer capacitors with energy-storage density of 14 J·cm −3 by heterovalent-doping-enabled atom-displacement fluctuation.

GeTe is a promising mid-temperature thermoelectric compound but inevitably contains excessive Ge vacancies hindering its performance maximization. This work reveals that significant enhancement in the dimensionless figure of merit ( ZT ) could be realized by defect structure engineering from point defects to line and plane defects of Ge vacancies. The evolved defects including dislocations and nanodomains enhance phonon scattering to reduce lattice thermal conductivity in GeTe. The accumulation of cationic vacancies toward the formation of dislocations and planar defects weakens the scattering against electronic carriers, securing the carrier mobility and power factor. This synergistic effect on electronic and thermal transport properties remarkably increases the quality factor. As a result, a maximum ZT  > 2.3 at 648 K and a record-high average ZT (300-798 K) were obtained for Bi 0.07 Ge 0.90 Te in lead-free GeTe-based compounds. This work demonstrates an important strategy for maximizing the thermoelectric performance of GeTe-based materials by engineering the defect structures, which could also be applied to other thermoelectric materials. The intrinsic high-concentration Ge vacancies in GeTe-based thermoelectric materials hinder their performance maximization. Here, the authors find that defect structure engineering strategy is effective for performance enhancement.

Parkinson's disease (PD) is strongly associated with life style, especially dietary habits, which have gained attention as disease modifiers. Here, we report a fasting mimicking diet (FMD), fasting 3 days followed by 4 days of refeeding for three 1-week cycles, which accelerated the retention of motor function and attenuated the loss of dopaminergic neurons in the substantia nigra in 1-methyl-4-phenyl-1,2,3,6-tetrathydropyridine (MPTP)-induced PD mice. Levels of brain-derived neurotrophic factor (BDNF), known to promote the survival of dopaminergic neurons, were increased in PD mice after FMD, suggesting an involvement of BDNF in FMD-mediated neuroprotection. Furthermore, FMD decreased the number of glial cells as well as the release of TNF-α and IL-1β in PD mice, showing that FMD also inhibited neuro-inflammation. 16S and 18S rRNA sequencing of fecal microbiota showed that FMD treatment modulated the shifts in gut microbiota composition, including higher abundance of Firmicutes, Tenericutes, and Opisthokonta and lower abundance of Proteobacteria at the phylum level in PD mice. Gas chromatography-mass spectrometry and liquid chromatography-mass spectrometry revealed that FMD modulated the MPTP-induced lower propionic acid and isobutyric acid, and higher butyric acid and valeric acid and other metabolites. Transplantation of fecal microbiota, from normal mice with FMD treatment to antibiotic-pretreated PD mice increased dopamine levels in the recipient PD mice, suggesting that gut microbiota contributed to the neuroprotection of FMD for PD. These findings demonstrate that FMD can be a new means of preventing and treating PD through promoting a favorable gut microbiota composition and metabolites.

The abnormal production of short chain fatty acid (SCFAs) caused by gut microbial dysbiosis plays an important role in the pathogenesis and progression of Parkinson’s disease (PD). This study sought to evaluate how butyrate, one of SCFAs, affect the pathology in a subacute 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine hydrochloride (MPTP) treated mouse model of PD. Sodium butyrate (NaB; 165 mg/kg/day i.g . , 7 days) was administrated from the day after the last MPTP injection. Interestingly, NaB significantly aggravated MPTP-induced motor dysfunction ( P  < 0.01), decreased dopamine ( P  < 0.05) and 5-HT ( P  < 0.05) levels, exacerbated declines of dopaminergic neurons (34%, P  < 0.05) and downregulated expression of tyrosine hydroxylase (TH, 47%, P  < 0.05), potentiated glia-mediated neuroinflammation by increasing the number of microglia (17%, P  < 0.05) and activating astrocytes (28%, P  < 0.01). In vitro study also confirmed that NaB could significantly exacerbate pro-inflammatory cytokines expression (IL-1β, 4.11-fold, P  < 0.01; IL-18, 3.42-fold, P  < 0.01 and iNOS, 2.52-fold, P  < 0.05) and NO production (1.55-fold, P  < 0.001) in LPS-stimulated BV2 cells. In addition, NaB upregulated the expression of pro-inflammatory cytokines (IL-6, 3.52-fold, P  < 0.05; IL-18, 1.72-fold, P  < 0.001) and NLRP3 (3.11-fold, P  < 0.001) in the colon of PD mice. However, NaB had no effect on NFκB, MyD88 and TNF-α expression in PD mice. Our results indicate that NaB exacerbates MPTP-induced PD by aggravating neuroinflammation and colonic inflammation independently of the NFκB/MyD88/TNF-α signaling pathway.

(K,Na)NbO 3 -based ceramics are deemed among the most promising lead-free piezoelectric materials, though their overall piezoelectric performance still lags behind the mainstream lead-containing counterparts. Here, we achieve an ultrahigh piezoelectric charge coefficient d 33 ∼ 807 pC·N −1 , along with a high longitudinal electromechanical coupling factor (k 33  ∼ 88%) and Curie temperature (T c  ∼ 245 °C) in the (K,Na)(Nb 1- x Sb x )O 3 -Bi 0.5 Na 0.5 ZrO 3 -BiFeO 3 (KNN- x Sb) system through structural flexibility and grain orientation strategies. Phenomenological models, phase field simulations and high-angle annular dark-field scanning transmission electron microscopy reveal that the structural flexibility originates from the high Coulomb force between K + /Na + ions and Sb ions in the KNN- x Sb system, while the grain orientation promotes the displacement of B-site cations leveraging the engineered domain configuration. As a result of its excellent comprehensive piezoelectric properties, the textured KNN-5Sb/epoxy 1-3 piezoelectric composite is found to possess a broader bandwidth BW = 60% and higher amplitude output voltage than commercial PZT-5 and other KNN counterparts. These findings suggest that the textured KNN-5Sb ceramics could potentially replace current lead-based piezoceramics in transducer applications. The authors achieve piezoelectric coefficient d 33 ∼ 807 pC·N −1 , along with high k 33 ∼ 88 % and T c ∼ 245 °C in (K,Na)(Nb 1- x Sb x )O 3 -Bi 0.5 Na 0.5 ZrO 3 -BiFeO 3 system through structural flexibility and grain orientation strategies.

A series of solid solution of (1− x )BiFeO 3 – x BaTiO 3 (abbreviated as BFO– x BT at 0.24 ≤  x  ≤ 0.34) were prepared to reveal the relation between phase structure and multiferroic properties. A morphotropic phase boundary (MPB) separating R phase and T one was detected in BFO– x BT system at 0.26 ≤  x  ≤ 0.34. Due to R and T two - phase coexistence, high piezoelectric properties of d 33  = 191 pC/N and k p  = 34.68%, as well as excellent ferroelectric properties of 2 P r  = 56.13 μm/cm 2 and 2 E C  = 75.35 kV/cm were achieved in the BFO– x BT ceramics at x  = 0.30. Moreover, a low leakage current density ( J ) of 1.01 × 10 −6 –3.18 × 10 −6  A/cm 2 at an applied electric field of 30 kV/cm and a weak ferromagnetism with remanent magnetization M r of 0.014–0.054 emu/g and coercive fields H c of 946–2340 Oe were detected in BFO– x BT ceramics at 0.24 ≤  x  ≤ 0.34, suggesting that the BFO–BT ceramics have promising prospects in magnetoelectric functional components.

Thermoelectric materials, which directly convert heat into electricity based on the Seebeck effects, have long been investigated for use in semiconductor refrigeration or waste heat recovery. Among them, SnSe has attracted significant attention due to its promising performance in both p-type and n-type crystals; in particular, a higher out-of-plane ZT value could be achieved in n-type SnSe due to its 3D charge and 2D phonon transports. In this work, the thermoelectric transport properties of n-type polycrystalline SnSe were investigated with an emphasis on the out-of-plane transport through producing textural microstructure. The textures were fabricated using mechanical alloying and repeated spark plasma sintering (SPS), as a kind of hot pressing, aimed at producing strong anisotropic transports in n-type polycrystalline SnSe as that in crystalline SnSe. Results show that the lowest thermal conductivity of 0.36 Wm-1 K-1 was obtained at 783 K in perpendicular to texture direction. Interestingly, the electrical transport properties are less anisotropic and even nearly isotropic, and the power factors reach 681.3 μWm-1 K-2 at 783 K along both parallel and perpendicular directions. The combination of large isotropic power factor and low anisotropic thermal conductivity leads to a maximum ZT of 1.5 at 783 K. The high performance elucidates the outstanding electrical and thermal transport behaviors in n-type polycrystalline SnSe, and a higher thermoelectric performance can be expected with future optimizing texture in n-type polycrystalline SnSe.

Optical absorption and photocatalytic activity can be enhanced by surface plasmon resonance (SPR) effect, but the charge transfer (CT) mechanism between the dispersed noble metal nanoparticles (NPs) and the semiconductor matrix has been ignored. Herein, we adduce a direct and strong evidence in Ag-nanoparticle-dispersed BaTiO 3 (Ag/BTO) composite films through X-ray photoelectron and photoluminescence spectra which reveals the CT from BTO trapped by Ag NPs under UV light and from Ag NPs to BTO under visible light. Owing to the broadened optical absorption and efficient CT from Ag NPs to BTO, the Ag25/BTO film manifests the optimal photocatalytic activity under the irradiation of visible light rather than UV–Vis light. Our work provides a helpful insight to design highly efficient plasmonic photocatalyst through considering the synergetic effect of the CT between metal and semiconductor on the enhanced photocatalytic activity.

The enhanced piezoelectric and ferroelectric properties of the tetragonal 0.67BiFeO 3 –0.33BaTiO 3 (BF–33BT) ceramics without MnO 2 doping or other dopants via tailoring sintering temperature ( T S ) and dwell time ( t d ) are reported. All ceramics crystallized in a single tetragonal phase, independent of the adopted T S and t d . As the T S or t d is increased, the BF–33BT ceramics show an increase in grain size and in relative density, while T S  > 980 °C or t d  > 6 h would result in more oxygen vacancies caused by Bi 3+ evaporation and/or reduction of Fe 3+ to Fe 2+ , along with a reduced relative density and an increased current leakage density. Because of the increased grain size, the higher relative density, and relatively less oxygen vacancies, high d 33  = 151 pC/N and P r  = 25.9 μC/cm 2 were achieved in tetragonal BF–33BT ceramics with T S  = 980 °C and t d  = 6 h. In addition, large unipolar strain of 0.146% and d 33 ∗ =326 pm/V (40 kV/cm), as well as high T C  = 427 °C were also obtained in the BF–33BT ceramics with T S  = 980 °C and t d  = 6 h. Our studies indicate that the grain size, the relative density, and the oxygen vacancies play important roles for the piezoelectric properties of BF–33BT ceramics.

The liquid-like feature of thermoelectric superionic conductors is a double-edged sword: the long-range migration of ions hinders the phonon transport, but their directional segregation greatly impairs the service stability. We report the synergetic enhancement in figure of merit (ZT) and stability in Cu 1.99 Se-based superionic conductors enabled by ion confinement effects. Guided by density functional theory and nudged elastic band simulations, we elevated the activation energy to restrict ion migrations through a cation–anion co-doping strategy. We reduced the carrier concentration without sacrificing the low thermal conductivity, obtaining a ZT of ∼3.0 at 1,050 K. Notably, the fabricated device module maintained a high conversion efficiency of up to ∼13.4% for a temperature difference of 518 K without obvious degradation after 120 cycles. Our work could be generalized to develop electrically and thermally robust functional materials with ionic migration characteristics. Cu 2 Se is of interest for thermoelectrics as it is environmentally sustainable and has a high figure of merit ZT; however, copper ion migration impacts device stability. Here a co-doping strategy that combines steric and electrostatic effects is shown to improve device stability as well as improving ZT to 3.