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Owing to the flammability of dendrites and organic liquid electrolytes, the safety performance of lithium-ion batteries cannot be effectively ensured. The sodium-ion solid electrolyte is anticipated to become the leading next generation battery in commercial applications due to the high thermal stability and low price. Yet, the insufficient ionic conductivity of Na3Zr2Si2PO12 solid electrolytes, along with the large interfacial resistance between the cathode material and the solid electrolyte, substantially restricts the performance of room-temperature all-solid-state sodium rechargeable batteries. In the present study, the effects of Bi2O3 additive on the phase, microstructure and ionic conductivity of Na3.1Y0.1Zr1.9Si2PO12 ceramic electrolyte are reported. Moreover, a significant room temperature conductivity of 1.21 × 10-3 S cm-1 and the dense microstructure was attained by adding 1 wt% Bi2O3 to Na3.1Y0.1Zr1.9Si2PO12 sintered at 1100 °C for 6 h. Simultaneously, an electrochemical test exhibited that the electrochemical stability window increased to 4.8 V and revealed good cycle stability.

Inorganic ceramic as one of the most promising candidate for solid state electrolytes (SSEs) have received extensive attention due to their excellent thermal stability, good electrochemical stability and wide electrochemical window. The sodium super ionic conductor (NASICON, Na3Zr2Si2PO12) structure possesses a three-dimensional network, which helps the migration of Na+. However, because of its low Na+ ion conductivity and poor sintering performance, Na3Zr2Si2PO12 is difficult to achieve application. Therefore, it is quite urgent to solve these questions. In this study, we have reported the effects of additive antimony-tin oxide (ATO) on the phase, microstructure and ionic conductivity of Na3Zr2Si2PO12 ceramic electrolytes. With the ATO sintering additive added, the Na+ ion conductivity and density of Na3Zr2Si2PO12 ceramic electrolytes were improved. The Na3Zr2Si2PO12 ceramic with 5 wt% ATO additive sintered at 1100 °C shows a relatively high ionic conductivity of 1.43 × 10 − 3 S cm-1 at room-temperature, most densest microstructure and wide electrochemical window up to 4.6 V (vs. Na/Na+). In addition, Na/NASICON/Na symmetrical cells were assembled and exhibited good cycling stability which implied good compatibility between sodium (Na) metal and NASICON electrolyte.

Oxygen reduction reaction (ORR) of La 0.8 Sr 0.2 Co 0.5 Fe 0.5 O 3-δ (LSCF) cathode on La 9.5 Si 6 O 26.25 (LSO) apatite electrolyte is studied by electrochemical impedance spectroscopy over the temperature range 700–850 °C and the oxygen partial pressure range 0.01–0.21 atm. Different to the ORR on the LSCF electrode on Gd-doped ceria (GDC) electrolyte, the impedance response for the ORR on the LSCF electrode on LSO apatite electrolyte is characterized by clearly separable arcs at high, intermediate and low frequencies. The high frequency electrode process has activation energy of 231 ± 7 kJ mol −1 and is basically independent of oxygen partial pressure, which is most likely associated with the oxygen ion transfer from the LSCF electrode to LSO electrolyte at the interface. On the other hand, the electrode processes associated with the low and intermediate frequency arcs are dependent on the oxygen partial pressure with activation energies of 192 ± 12 kJ mol −1 and 124 ± 28 kJ mol −1 , respectively, are related to the dissociative adsorption and diffusion of oxygen on the LSCF surface and through the bulk and/or pores of LSCF electrodes to the reaction sites. The results show that the diffusion and migration of silica from the LSO apatite electrolyte to the LSCF surface particularly at the interface region have significant adverse effect on the electrochemical activity of LSCF cathode.

Lanthanum silicate oxyapatites with and without calcium (Ca) and iron (Fe) doping, La 10 Si 5 FeO 26.5 (LSFO) and La 9.5 Ca 0.5 Si 5.5 Fe 0.5 O 26.5 (LCSFO), are synthesized by sol–gel process (SGP) and solid state reaction process (SSP). The phase formation, microstructure and conductivities of LSFO and LCSFO oxyapatites are characterized by X-ray diffraction (XRD), scanning electron spectroscopy (SEM) and complex impedance analysis. The morphologies of LCSFO oxyapatite nanoparticles synthesized by SGP were characterized by transmission electron microscope (TEM). The thermal and decomposition properties of the LCSFO gel were analyzed by simultaneous differential scanning calorimetry and thermal gravimetric analysis (DSC–TGA). The results show that the phase formation of LCSFO synthesized by SGP occurs at temperatures as low as 750 °C, significantly lower than ∼1500 °C required for LCSFO synthesized by SSP. Co-doping of Ca and Fe significantly improves the densification, sinterability and oxide-ion conductivity of lanthanum silicate oxyapatites. The best results were obtained on LCSFO synthesized by SGP, achieving oxide-ion conductivity of 2.08 × 10 −2 S cm −1 at 800 °C, which is higher than 5.68 × 10 −3 S cm −1 and 1.04 × 10 −2 S cm −1 for LSFO and LCSFO synthesized by SSP, respectively, under the identical test conditions.

Electroless silver coating of carbonyl iron powder is demonstrated in the present investigation. The carbonyl iron powders are characterized by scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDX), and X-ray diffraction analysis (XRD) before and after the coating process. The relatively uniform and continuous silver coating is obtained under the given coating conditions. In this paper, the electromagnetic interference (EMI) shielding mechanism of the silver-coated carbonyl iron powder is suggested. The reflection of silver coating and absorption of carbonyl iron powder dominate the shielding mechanism of the silver-coated carbonyl iron powder. The silver-coated carbonyl iron powders are used as conductive filler in electroconductive adhesive for electromagnetic interference shielding applications. The effect of the thickness of electroconductive adhesive on the shielding effectiveness (SE) is investigated. The results indicate that the SE increases obviously with the increase of the thickness of electroconductive adhesive. The SE of the electroconductive adhesive with 0.35 mm thickness is above 38 dB across the tested frequency range.

The effect of co-doping of Sr and Al or Fe on the microstructure, sinterability and oxide-ion conductivity of lanthanum silicate oxyapatites is investigated in detail at 300–800 °C by the electrochemical impedance spectroscopy. The oxide-ion conductivity is 1.46 × 10 −2 S cm −1 for La 9.5 Sr 0.5 Si 5.5 Fe 0.5 O 26.5 (LSSFO) and 1.34 × 10 −2 S cm −1 at 800 °C for La 9.5 Sr 0.5 Si 5.5 Al 0.5 O 26.5 (LSSAO), respectively, which is one order of magnitude higher than 6.16 × 10 −3 S cm −1 measured on La 9.67 Si 6 O 26.5 (LSO) oxyapatite under the identical test conditions. The grain bulk and grain boundary resistances of co-doped oxyapatite are significantly smaller than that of LSO oxyapatite, and decrease significantly with the increase of the sintering temperature. LSSFO and LSSAO also show significantly higher density as compared to that of LSO. The results indicate that co-doping of Sr and Al or Fe significantly improves the densification, sinterability and oxide-ion conductivity of lanthanum silicate oxyapatites.

Oxygen reduction reaction of (La,Sr)MnO3 (LSM) cathode on La9.5Si6O26.25 apatite (LSO) electrolyte is studied over the temperature range 750–900 °C and the oxygen partial pressure range 0.01–1 atm by electrochemical impedance spectroscopy. The impedance responses show two separable arcs and are analyzed in terms of two different equivalent circuits with comparable information on the electrode processes at high and low frequencies. The electrode process associated with the high frequency arc (σ1) is basically independent of oxygen partial pressure. The activation energy of σ1 is 188 ± 15 kJ mol−1 for the O2 reduction reaction on the LSM electrode sintered at 1150 °C, and decreases to 120 kJ mol−1 for the O2 reduction reaction on the LSM electrode sintered at 850 °C, which is close to 80–110 kJ mol−1 observed for the same electrode process at LSM/YSZ interface. The reaction order with respect to P O 2 and the activation energy of the electrode process associated with low frequency arc (σ2) are generally close to that of σ2 at the LSM/YSZ interface. The activation process of the cathodic polarization treatment is noticeably slower for the reaction at LSM/LSO interface as compared to that at LSM/YSZ interface. The impedance responses of O2 reduction reaction at the LSM/LSO interface are significantly higher than that at the LSM/YSZ interface due to the silicon spreading. The impedance responses decrease with the decrease of the sintering temperature of LSM electrode on LSO electrolyte. At the sintering temperature of 1000 °C, the impedance responses of O2 reduction reaction is 1.74 Ω cm2 at 900 °C, which is significantly smaller than that of LSM electrode sintered at 1150 °C.

Electroless silver coating on copper powder and its effects on oxidation resistance were investigated. In general, silver-coated copper powder is prepared by an electroless type of substitution plating making use of the substitution reaction between copper and silver. However, [Cu (NH 3 ) 4 ] 2+ is produced during the electroless plating process and absorbed onto the surface of the copper particles, which prevent substitution reactions proceeding. In the new electroless plating process, RE-608 copper-specific extractant was used as chelating reagent to formed chelate compound with Cu 2+ and the chelate compound was extracted to organic phase, which confirmed substitution reaction to be proceeding. As-coated copper particles were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). When the silver content reached 6.86 wt.%, silver was homogeneously distributed around the copper particles and few free silver particles were detected. The results indicated that the properties of oxidation resistance were improved with increasing the dosage of RE-608 copper-specific extractant and reaction time, and with decreasing AgNO 3 concentration. It was also found that the optimum reaction temperature was 80 °C.

Apatite ceramics are interesting alternative solid oxide fuel cells (SOFCs) electrolytes because of their open structure for the transportation of oxide ions and their good chemical stability. This study reports the influence of barium doping on the microstructure, sinterability and oxide conductivity properties of the aluminium lanthanum oxyapatite La9.5Ba0.5Si5.5Al0.5O26.5. SEM results show that lanthanum substitution with barium improves the sinterability of apatite ceramics. The barium doping also enhances the conductivity of the aluminium lanthanum silicates. The oxygen ion conductivity of La9.5Ba0.5Si5.5Al0.5O26.5 sintered at 1600 °C is 2.21 × 10−2 S cm−1 at 800 °C, higher than 9.81 × 10−3 S cm−1 of La10Si5AlO26.5 sample prepared under the same conditions. The results in the present study demonstrate that doping Ba on the La site for aluminium lanthanum oxyapatite reduces the sintering temperature and improves the ion conductivity. The enhancement of Ba dopant is mainly on the improvement of the densification and thus substantially reduced grain boundary resistance of aluminium lanthanum oxyapatite particularly at low temperatures