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The effects of transition elements Fe, Co, and Ni on the electronic structure and thermoelectric properties of β-Zn 4 Sb 3 were investigated by performing self-consistent ab initio electronic structure calculations within density functional theory and solving the Boltzmann transport equations within the relaxation time approximation. The results demonstrate that these transition elements with 3 d orbitals could introduce giant sharp resonant peaks in the electronic density of states (DOS) near the host valence band maximum or conduction band minimum in energy. And these deliberately engineered DOS peaks result in a sharp increase of the room-temperature Seebeck coefficient of β-Zn 4 Sb 3 by a factor of nearly 60, 80 and 130, respectively. Additionally, with the simultaneous decline of carrier thermal conductivity upon Co/Ni doping, potentially, at least, 1.21/1.13-fold increase in thermoelectric figure of merit of β-Zn 4 Sb 3 at room temperature are achieved, indicating that the substitution of Co and Ni for Zn can effectively elevate thermoelectric performance of β-Zn 4 Sb 3. • Investigated Fe/Co/Ni's doping effects on β-Zn 4 Sb 3. • Found giant sharp resonant peaks in the electronic density of states (DOS). • Found a boost in the Seebeck coefficient of β-Zn 4 Sb 3 at 300 K. • Achieved great increase in thermoelectric figure of merit of β-Zn 4 Sb 3 at 300 K. [ABSTRACT FROM AUTHOR]

Abstract Hollow SnO 2 nanospheres have been successfully fabricated through a simple hydrothermal method by using carbon spheres as template. Microstructure observation showed that the hollow SnO 2 had uniform nanoscale size and single-shelled structure assembled by individual nanocrystallines. Being employed as the supercapacitor electrode materials, the resultant hollow SnO 2 nanospheres displayed a considerable specific capacitance of 332.7 F/g at a current density of 1 A/g, much higher than the pristine SnO 2 particles (143.5 F/g). The hollow SnO 2 also exhibited good rate capability remained relatively high capacitance of 174.9 F/g at a large current density of 20 A/g, as well as excellent cycling properties without capacitance degradation over 2000 charging/discharging cycles. Such excellent electrochemical performance of the hollow SnO 2 nanosphere can be attributed to its unique nanosized and single-shelled hollow structure which greatly increases the available surface area and providing hierarchical porosity for the electrode materials. Highlights • Hollow SnO 2 nanospheres were successfully fabricated by a hydrothermal method. • The hollow SnO 2 possesses novel nanoscale size and single-shelled structure. • The hollow SnO 2 exhibited enhanced capacitive properties. [ABSTRACT FROM AUTHOR]

The evolutions of phase transformation, magnetic and electrical transport properties with the change of Fe concentration have been systematically investigated in a series of Ni 60- x Fe 13+ x Ga 27 (x = 0–10) Heusler alloys. The structure and heat flow measurements reveal every sample undergoes a disordered-ordered transition from a disordered B 2 structure to a L 2 1 ordered structure, and a first-order structural transformation from the L 2 1 cubic structure to a L 1 0 tetragonal structure is corresponding to the martensitic transformation (MT). With increasing Fe concentration, the disordered-ordered transition and ferromagnetic transition shift to higher temperature, while the MT shifts to lower temperature. According to phase diagram established in the present investigation, it is also found that the increase of Fe content can convert the first-order MT from a paramagnetic type to a ferromagnetic one, which is accompanying by an obvious increase of both effective and spontaneous magnetic moments. Furthermore, the calculated magnetocrystalline anisotropy constant (K 1) of the studied alloys monotonically increases as Fe increases. It is evident that the magnetic degrees of freedom in these two MTs remain almost unchanged so that the electron-spin scattering doesn't change, which results in the resistivity difference between the austenitic and martensitic states is feeble. Such an intrinsic nature leads to a weak magnetoresistance (MR) and baroresistance (BR) effects in the studied samples because of only contribution of electron-lattice scattering change on the resistivity. This demonstrates from a negative perspective that the electron-spin scattering change originated from the variation in the magnetic degrees of freedom acts as a dominant role in improvement of the MR and BR effects for the Heusler system possessed the first-order MT. • The phase diagram including the structural ordering transition for Ni-Fe-Ga alloys was established. • Ni 60- x Fe 13+ x Ga 27 alloys undergo a disordered-ordered transition from a disordered B 2 structure to a L 2 1 ordered structure. • The magnetocrystalline anisotropy constant monotonically increases as Fe increases. • The baroresistance and magnetoresistance effect of Ni-Fe-Ga has been obtained around the room temperature. • The electron-spin scattering change acts as a crucial role to improve the MR and BR effects. [ABSTRACT FROM AUTHOR]

Silver niobate (AgNbO 3 , AN) dielectric ceramics and their antiferroelectric behavior have attracted increasing attention for their potential applications in energy-storage capacitors. However, AN's inferior dielectric breakdown strength, recoverable energy storage density, and efficiency have limited its application. In this work, a combination of chemical composition design and liquid-phase sintering was considered for the fabrication of highly insulated and desensitized AN-based ceramics for enhancing E b , W rec , and η of AN. We design and prepare (1 − x)AgNbO 3 - x (Sr 0.7 Bi 0.2)HfO 3 (AN-100 x SBH, x = 0.00–0.06) ceramics with the addition of 1 mol% BaCu(B 2 O 5) (BCB) as a sintering aid to realize this. It is found that highly desensitized ceramics can be formed at 1000–1030 °C over the course of 2 h. The electrical property characterization results indicate that the AFE state and E b are significantly enhanced with increasing SBH concentration. High W rec and η values of 6.1 J/cm3 and 73%, respectively, under an applied field of 330 kV/cm are achieved in the AN-5.5SBH ceramic. Meanwhile, the AN-5.5SBH ceramic shows excellent thermal stability over a wide temperature range (25–120 °C) under an externally applied field of 290 kV/cm, in which the fluctuations of W rec and η are 3.8% and 1.5%, respectively. These results provide an effective method for obtaining AN-based ceramics with excellent electrical properties under a lower sintering temperature than that required for pure AN ceramics. This method could be further generalized to develop new lead-free energy-storage dielectric materials. • AgNbO3-based dielectric ceramics with stabilized antiferroelectricity synthesized. • Ceramics with dense microstructure successfully sintered at 1000–1030 °C for 2 h. • High recoverable energy storage density (6.1 J/cm3) and efficiency value (73%) achieved. • Energy storage properties stable over the temperature range of 25–120 °C. [ABSTRACT FROM AUTHOR]

An experimental investigation was conducted to understand the influence of hydrostatic pressure on phase transition, thermal expansion and barocaloric property of a polycrystalline Ni 54 Mn 23 Ga 23 alloy. Two pressure ranges of 0–1.28 GPa and 0–0.74 GPa were selected for thermal expansion and barocaloric property measurements due to the different test limits of instrumentals. The pressure dependence of fourteen parameters was studied systematically. It was found that the sample experiences a martensitic transformation (MT) near room temperature and the response of MT peak temperature (T M) to pressure is about 15.89 K/GPa. The phase transition strain (λ tr), transformation width (Δ T tr) relative volume change (|Δ V / V |) and maximum adiabatic temperature change (Δ T ad) max increase linearly with pressure and their shifting rates are about 0.071 %/GPa, 7.5 K/GPa, 0.211 %/GPa and 12.2 K/GPa, respectively. Simultaneously, applying hydrostatic pressure can also enhance the barocaloric property of the sample, leading to a large increase in the absolute value of the maximum entropy change (|Δ S | max), the refrigerating capacity (RC) and their reversible values. On cooling, the sensitivities of the reversible RC and its proportion to pressure are around 185.52 J/kg GPa and 16.7 %/GPa, respectively. Finally, the average linear expansion coefficient (α ave) of both martensite and austenite phases keeps unchanged while in the MT region it decreases from -99.84×10–6/K to -86.04×10–6/K with increasing pressure from 0 to 1.28 GPa. These findings indicate that applying hydrostatic pressure can effectively adjust the phase transformation, thermal expansion and barocaloric property of Ni-Mn-Ga alloys, which are meaningful for their application in solid-state refrigeration. • Pressure can effectively adjust phase transformation, thermal expansion and barocaloric property of Ni 54 Mn 23 Ga 23 alloy. • A large response of martensitic transformation (MT) peak temperature to pressure is reported. • The barocaloric property and its reversibility are highly sensitive to pressure. • The average linear expansion coefficient during MT decreases with increasing pressure. [ABSTRACT FROM AUTHOR]

Surface engineering of transition metal oxide cathode materials for Li-ion batteries is highly important to achieve high-capacity retention, high-rate capability, and long-life term. In this study, VSe 2 nanosheets are prepared and used as a surface sensitizer to enhance the electrochemical properties of LiFePO 4 (LFP) cathode material. The LiFePO 4 @VSe 2 (LFP@VSe 2) composite is formed by anchoring 1D-LFP particles with the as-prepared 2D-VSe 2 nanosheets by using an in-situ solution phase technique. When the LFP@VSe 2 composites are used as cathode materials for Li-ion batteries, the Li surface-controlled storage behavior of the batteries is reasonably enhanced. The performance is attributed to the improvement in the inherent Li-ion conductivity of LFP particles, thereby inhibiting surface diffusion drawbacks and decreasing charge transfer resistance. The exterior VSe 2 attached to the LFP serves as a second electrically conducting layer to increase conductivity into the entire electrode. Thus, these conditions enhance the electron transfer kinetics and surface stability of the LFP cathode. LFP@VSe 2 composite cathode exhibits an ultrastable specific capacity of 166.5 mAh g−1 after 100 cycles @ 0.1 C and can retain a specific capacity of 146.7 and 46.5 mAh g−1 after 700 and 2000 cycles respectively at a current rate of 0.3 C and 10 C. • LiFePO 4 @VSe 2 composite electrode material is prepared via in situ solution phase doping of the as-synthesized VSe 2 nanosheets on the surface of LiFePO 4. • Lithium-ion battery employing LiFePO 4 @VSe 2 composite cathode with ultrahigh capacity of 168.8 mAh g−1 at 0.1 C and highly stable performance has been achieved. • Lithium-ion full cell employing LiFePO 4 @VSe 2 composite cathode and hard carbon anode showed significant improvement in cycle performance. • This approach reveals the importance of 2-dimensional (2D) transition metal dichalcogenides doping on the surface of transition metal oxide cathode for practical application. [ABSTRACT FROM AUTHOR]

Effects on substitution of Ge by In on structural and magnetic properties are studied in MnCoGe 1- x In x compounds. A small amount of In (2% and 5%) dopant can shift the martensite transformation temperature to room temperature and make it overlap with Curie temperature window, which results in a spin-lattice coupling and a large conventional magnetocaloric effect. Giant values of magnetic entropy change ( △S M ) are obtained in both magnetizing and demagnetizing processes in the vicinity of the magnetostructural transition. The maximum values of | △S M | for MnCoGe 0.95 In 0.05 reach 21.4 and 25.4 J/kg K for a small magnetic field change △H  = 2–0 and 0–2 T, respectively, which make it promising for room temperature magnetic refrigeration applications. [ABSTRACT FROM AUTHOR]

Both the barocaloric effect (BCE) and its reversible behavior during martensitic transformation (MT) have been experimentally investigated in Ni 42.3 Co 7.9 Mn 38.8 Sn 11 quaternary Heusler alloy. The experimental results show that the studied alloy experiences the MT from the ferromagnetic L 2 1 -type cubic structure to the paramagnetic-like three-layered (3 M ) modulated monoclinic structure, resulting in a value of ∼1.1% for the relative volume change ε between two phases. Due to appearance of an enhanced ε , the migration rate of martensitic transformation with respect to the hydrostatic pressure reaches ∼4.7 K/kbar, while a high transition entropy change (∼28 J/kg K) is still maintained. Based on an indirectly estimated method, the calculated maximum value for isothermal entropy change Δ S T achieves ∼ -23 J/kg K with the pressure change of 6.2 kbar, which yields the values of ∼10 K for adiabatic temperature change Δ T a d and ∼786 J/kg for relative cooling power (RCP), performing a large BCE. According to the change of phase fraction at selected hydrostatic pressures, a detailed schematic diagram has been established to evaluate the reversibility of this effect. With applying an external cyclic pressure of 6.2 kbar, the maximum repeatable values calculated for both Δ S T and Δ T a d are decreased to ∼ -15 J/kg K and ∼5 K, respectively. This is attributed to an insufficient driving force, which can only partially transform this material, leading to a reversible MT appeared in the mixed state. [ABSTRACT FROM AUTHOR]

The crystal structures, martensitic transformations (MT) and magnetic properties of polycrystalline Ni 56- x Co x Mn 18 Ga 26 ( x = 0, 1, 2) alloys have been investigated comprehensively. These alloys exhibit an unmodulated martensitic structure ( L 1 0 ) at room temperature. In the Co free alloy, a magneto-structural coupling MT is presented. With increasing Co content, however, the MT moves to a higher temperature and finally partly splits off from ferromagnetic transition at x = 2. Simultaneously, two successive magneto-structural transformations were observed at x = 1, which could be ascribed to the existence of an intermartensitic transition (7 M ↔ L 1 0 ). Owing to the evolution of MT with Co doping, the magnetization of paramagnetic (PM) austenite is increased slightly, while the ferromagnetic (FM) martensite is almost unchanged. The multiple functional properties associated with the field-induced MT were also investigated in these alloys. It was found that the optimized magnetostrain amounts to ∼0.12% in the alloy with x = 2. In addition, the refrigerant capacity (RC) with the values of 50 J/kg and 49 J/kg were obtained in the alloy with x = 0 and x = 1, respectively. [ABSTRACT FROM AUTHOR]

The influence of isotropic physical pressure, applied either during the high-pressure-high-temperature (HPHT) annealing or the measuring processes, on the magnetic properties of NdFeO 3 single crystal, has been investigated. In comparison to the complete spin reorientation (SR) in an as-grown NdFeO 3 single crystal, the thermomagnetic M (T) and isothermal M (H) curves for a HPHT-annealed sample indicates an incomplete SR transition from a Γ 2 -rich to a Γ 4 -rich Γ 24 mixed phase. Moreover, the M (T) curves of the as-grown sample under different measuring hydrostatic pressures suggest that the SR transition takes place in the sequence of Γ 2 → Γ 1 + Γ 2 + Γ 4 → Γ 1 + Γ 4 → Γ 4 , instead of the Γ 2 → Γ 2 + Γ 4 → Γ 4, without applying pressure during the measuring process. Such manipulation of the magnetic configuration reveals that the 3 d -4 f interaction in the NdFeO 3 could be greatly affected by the isotropic pressure. These findings may provide a new perspective and possibility for the tuning of the magnetism and corresponding microscopic interactions. • A comparative study of isotropic pressure on NdFeO3 single crystal is carried out. • High-pressure-high-temperature annealing leads to an incomplete spin reorientation • Hydrostatic pressure in the measuring process introduces an intermediate phase. • Isotropic pressure can tune the magnetism and microscopic interactions in NdFeO3. [ABSTRACT FROM AUTHOR]

• Silver nanoparticles rapidly formed on the surfaces of carbon nanotubes by photothermal heating. • The field emission characteristics of Ag nanoparticles decorated carbon nanotubes were enhanced compared to carbon nanotubes. • The deposition of silver nanoparticles on carbon nanotubes improved the field emission stability. Silver (Ag) nanoparticles decorated on carbon nanotubes (CNTs) were rapidly formed by the photothermal heating provided by infrared (IR) irradiation. The method was implemented without any solvent, reductants and applied current. By optimizing the amount of precursors and photothermal heating time, the size of the silver nanoparticles could also be controlled. After decoration of the silver nanoparticles on carbon nanotubes, the field emission characteristics were noted to be enhanced, while the turn-on electric field (at the current density of 10 μA/cm2) and threshold electric field (at the current density of 1 mA/cm2) decreased. At 10% mol Ag loading, the current did not exhibit decay for four hours at the current density of 1 mA/cm2. [ABSTRACT FROM AUTHOR]

The evolutions of electrical transport property and Baroresistance (BR) effect at the martensitic transformation (MT) with the change of Co content have been systematically investigated in the Ni 50- x Co x Mn 35 In 15 (0 ≤ x ≤ 7) Heusler system. The structure measurements show that every sample undergoes first-order MT from a L 2 1 cubic structure to a 3 M monoclinic structure. According to magnetic measurements, it is also found that the samples with lower Co content (0 ≤ x ≤ 3) exhibit a paramagnetic MT, i.e. the MT occurs between the paramagnetic austenite and the paramagnetic martensite. At higher Co content, however, the samples display a metamagnetic MT, i.e. the MT occurs between the ferromagnetic austenite and the paramagnetic martensite. Due to the enhancement of the ferromagnetic ordering for the austenitic phase with Co increasing, the difference in resistivity between austenitic and martensitic phases is enlarged significantly. This leads to a giant BR effect with a value of ∼250% associated with the hydrostatic pressure-induced MT can be observed in the sample with x = 6. Moreover, the Hall measurement results indicate that the difference in electrical transport behavior between both phases for the studied alloys mostly relies on the mobility of carriers related to the electro-lattice and the electro-spin scatterings. In this case, the underlying mechanism of the relative contributions originating from these two different scattering processes to the saturated BR effect has been separated quantitively based on the electrical transport measurements under applied different hydrostatic pressures. It demonstrates that the electron-spin scattering acts as a dominant role in improvement of the BR effect for this system. • The MT from a paramagnetic type into a metamagnetic one has been found. • A giant BR effect (∼250%) has been obtained around the room temperature. • The change of electrical transport during MT depends on the mobility of carriers. • Both electro-lattice and electro-spin scatterings has been separated quantitively. • The spin-dependent scattering plays a crucial role to improve the BR effect. [ABSTRACT FROM AUTHOR]

The structural, magnetic, magnetocaloric and barocaloric properties were investigated in Ni 55.5 Mn 17.8 Ga 26.7 alloy. The results show that the sample experiences two successive magnetostructural transformations (MSTs) with decreasing/increasing temperature. The field-induced entropy change and pressure-induced entropy change are only −7.55 J/kg K for a field change of Δ H = 3 T and −10.52 J/kg K for a pressure change of Δ P = 0.622 GPa while the corresponding refrigeration capacity (RC) achieves 68.80 J/kg and 247.83 J/kg, respectively. Such considerable RC values can be ascribed to the broadening of the full-width at half maximum (FWHM) due to the two successive MSTs. It was observed that RC and FWHM increase with magnetic field and pressure, which results in an enhancement of magnetocaloric and barocaloric effects. Importantly, RC and FWHM under Δ P = 0.622 GPa are comparable to and even larger than those reported in some expensive rare-earth-based magnetic refrigerants. The responses of RC and FWHM to pressure are 89.05 J/kg GPa and 4.77 K/GPa for 0 ≤ P ≤ 0.3 GPa and the values are 654.57 J/kg GPa and 73.86 K/GPa for 0.3 ≤ P ≤ 0.622 GPa. The FWHMs of 11.23 K under Δ H = 3 T and of 32.83 K under Δ P = 0.622 GPa are obtained. All these excellent properties originated from two successive MSTs would make Ni 55.5 Mn 17.8 Ga 26.7 alloy promising as a new and inexpensive multicaloric material used in the solid refrigeration technology. • Ni 55.5 Mn 17.8 Ga 26.7 alloy exhibits two successive magnetostructural transformations (MSTs). • Large magnetocaloric and barocaloric effects were observed due to the two successive MSTs. • Two successive MSTs and hydrostatic pressure can effectively broaden the phase transforming temperature span. • A large refrigerant capacity of 247.83 J/kg was obtained under a pressure change of 0.622 GPa. • An inexpensive multicaloric material Ni 55.5 Mn 17.8 Ga 26.7 alloy was reported. [ABSTRACT FROM AUTHOR]