Highest Bulk Conductivity Research Articles

A comparative study of LiTa2PO8 ceramics prepared with different lithium sources

In advancing lithium-ion batteries, solid electrolytes like LiTa2PO8, a Li-ion conductor with high bulk conductivity (~10−3 S/cm), show promise for all-solid-state battery technology. Here, we investigate the impact of different Li sources and their excess on the structural, microstructural and electrical properties of LiTa2PO8 ceramics. Employing diverse characterization techniques, including XRD, MAS NMR, TMA, SEM/EDS, IS, DC potentiostatic polarization, and density measurements, we unveil significant impact of the source of lithium ions and its excess on electrical properties. The sample without excess LiNO3 source exhibited the highest σtot = 5.2×10−4 S/cm at 30°C. Notably, the grain conductivity remained constant at ca. 3 mS/cm, irrespective of the chosen lithium source and excess. The microstructural analysis uncovered correlations between variations in total ionic conductivity and changes in the nature and concentration of secondary phases. Additionally, it revealed the influence of the arrangement of grains affecting the grain boundaries and porosity regions.

High Conductivity and Diffusion Mechanism of Oxide Ions in Triple Fluorite-Like Layers of Oxyhalides.

Oxide ion conductors are attractive materials because of their wide range of applications, such as solid oxide fuel cells. Oxide ion conduction in oxyhalides (compounds containing both oxide ions and halide ions) is rare. In the present work, we found that Sillén oxychlorides, Bi2-xTexLuO4+x/2Cl (x = 0, 0.1, and 0.2), show high oxide ion conductivity. The bulk conductivity of Bi1.9Te0.1LuO4.05Cl reaches 10-2 S cm-1 at 431 °C, which is much lower than 644 °C of yttria-stabilized zirconia (YSZ) and 534 °C of La0.8Sr0.2Ga0.83Mg0.17O2.815 (LSGM). Thanks to the low activation energy, Bi1.9Te0.1LuO4.05Cl exhibits a high bulk conductivity of 1.5 × 10-3 S cm-1 even at a low temperature of 310 °C, which is 204 times higher than that of YSZ. The low activation energy is attributed to the interstitialcy oxide ion diffusion in the triple fluorite-like layer, as evidenced by neutron diffraction experiments (Rietveld and neutron scattering length density analyses), bond valence-based energy calculations, static DFT calculations, and ab initio molecular dynamics simulations. The electrical conductivity of Bi1.9Te0.1LuO4.05Cl is almost independent of the oxygen partial pressure from 10-18 to 10-4 atm at 431 °C, indicating the electrolyte domain. Bi1.9Te0.1LuO4.05Cl also exhibits high chemical stability under a CO2 flow and ambient air at 400 °C. The oxide ion conduction due to the two-dimensional interstitialcy diffusion is considered to be common in Sillén oxyhalides with triple fluorite-like layers, such as Bi1.9Te0.1RO4.05Cl (R = La, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, Lu) and Bi6-2xTe2xO8+xBr2 (x = 0.1, 0.5). The present study opens a new field of materials chemistry: oxide ion-conducting Sillén oxyhalides with triple fluorite-like layers.

Effect of addition of LiAlSiO4 on microstructure, phase composition, and electrical properties of Li1.3Al0.3Ti1.7(PO4)3–based solid electrolyte

Li1.3Al0.3Ti1.7(PO4)3 (LATP) NASICON-type ceramic, due to its high bulk conductivity, is believed to be one of the most appropriate material for application as solid electrolyte in all-solid-state lithium-ion batteries. However, its highly resistant grain boundaries strongly limit the total ionic conductivity. Therefore, in this work, an attempt has been made to overcome this problem by introducing a Li-ion conducting additive LiAlSiO4 (LASO) to LATP base matrix in order to provide more conduction paths for lithium ions between grains. The properties of Li1.3Al0.3Ti1.7(PO4)3–xLiAlSiO4 (0.02 ≤ x ≤ 0.1) composite system were studied by means of: high-temperature X-ray powder diffractometry (HTXRD), 6Li, 27Al, and 31P magic angle spinning nuclear magnetic resonance spectroscopy (MAS NMR), scanning electron microscopy (SEM), and impedance spectroscopy (IS) methods. The obtained ceramic LATP–LASO materials exhibited high values of bulk conductivity, above 10−3 S/cm, and good total conductivity, exceeding 10−4 S/cm. The factors responsible for the enhancement, but also for the deterioration of total conductivity, i.e. microstructure and grain boundaries, are identified and discussed in this work.

Room temperature persisting surface charge carriers driven by intense terahertz electric fields in a topological insulator Bi2Se3

Topologically protected surface current is highly promising for next-generation low-dissipation and disorder-tolerant quantum electronics and computing. Yet, electric transport from the co-existing bulk state dominates the responses of the Dirac surface state, especially at elevated temperatures relevant to technological applications. Here, we present an approach that convincingly showcases the generation, disentanglement, and precise control of enduring surface charge carriers on a topological insulator, Bi2Se3, with high bulk conductivity, all achieved at room temperature. By using pump–probe modulation spectroscopy under ultrabroadband driving tunable from 4 meV to 1.55 eV, we show the terahertz (THz) field-induced surface carriers by discovering their initial temporal responses dominant over high density trivial bulk carriers. Strikingly, the response of the induced surface carrier responses persists for more than ∼5 ps and is enhanced by reducing pump photon energy. The dynamics and lifetime of the distinct surface response manifest themselves as the enhanced THz pump-induced THz transmission, which directly correlates with the transient negative THz conductivity. Increasing the THz driving field reduces the induced surface carrier lifetime and identifies, particularly, an optimal pump field of Es ∼ 224 kV cm−1 for generating the dominant surface response relative to the bulk. This surface carrier dominant regime is suppressed by a joint effect of enhanced surface-bulk scattering and a more rapid saturation of surface excitation compared to the bulk that sets in above Es. The controllability of room temperature topologically surface carriers through pump photon energy offer compelling possibilities for extending this approach to other topological complex materials.

Enhanced room-temperature Na+ ionic conductivity in Na4.92Y0.92Zr0.08Si4O12

Developing cost-effective and reliable solid-state sodium batteries with superior performance is crucial for stationary energy storage. A key component in facilitating their application is a solid-state electrolyte with high conductivity and stability. Herein, we employed aliovalent cation substitution to enhance ionic conductivity while preserving the crystal structure. Optimized substitution of Y3+ with Zr4+ in Na5YSi4O12 introduced Na+ ​ion vacancies, resulting in high bulk and total conductivities of up to 6.5 and 3.3 ​mS ​cm−1, respectively, at room temperature with the composition Na4.92Y0.92Zr0.08Si4O12 (NYZS). NYZS shows exceptional electrochemical stability (up to 10 ​V vs. Na+/Na), favorable interfacial compatibility with Na, and an excellent critical current density of 2.4 ​mA ​cm−2. The enhanced conductivity of Na+ ​ions in NYZS was elucidated using solid-state nuclear magnetic resonance techniques and theoretical simulations, revealing two migration routes facilitated by the synergistic effect of increased Na+ ​ion vacancies and improved chemical environment due to Zr4+ substitution. NYZS extends the list of suitable solid-state electrolytes and enables the facile synthesis of stable, low-cost Na+ ion silicate electrolytes.

Understanding Criticality of Thermal Performance in Thermal Interface Material Applications

Thermal interface material (TIM) is used in between a heat generating component (e.g., microelectronic packaging) and a heat spreading component (e.g., heatsink or cooling plate) to create an effective path for the heat (Phonon) to travel. Standard heatsink and heat generating component surfaces are generally uneven and rough. Actual metal to metal contact is no more than 10%. These surface imperfections allow air to get trapped in between the two surfaces. Air, being a thermal insulator, prevents the heat from dissipating and thus the device/system fails to maintain the required operating temperature to meet the reliability and functionality needed. Replacing the air with the “right” thermal interface material is the focus of this research. TIM is a composite of thermally conductive fillers dispersed in a polymer matrix. A higher filler loading causes a higher bulk conductivity. Common practice among design engineers is to utilize output from thermal modelling & simulation to specify a TIM with a certain thermal conductivity to meet the system’s thermal needs. What many engineers miss is the impact of thermal boundary resistance that could have significant effect on the overall thermal management of the design. This paper discusses how to characterize thermal performance of TIM beyond the bulk thermal conductivity. Boundary/interfacial thermal resistance and impedance will be explored as a function of TIM wetting ability, bond line thickness and surface conditions. This paper will discuss the importance of thermal conductivity, thermal resistance/impedance in a real application scenario.

Preparation of Electrically Conducting Bamboo Paper Using Multi‐Walled Carbon Nanotubes

AbstractThe electrically conducting composite paper is prepared by incorporating the cellulosic pulp extracted mechano‐chemically from a bamboo species, Arundinaria falcata, locally called Nigalo, with different amounts of multi‐walled carbon nanotubes (MWCNTs). The raw and processed fibers as well as the composite papers with MWCNTs are examined with Fourier transform infrared (FTIR) spectroscopy, X‐ray diffraction (XRD), polarizing optical microscopy (POM), and scanning electron microscopy (SEM). The four‐probe method is utilized to quantify the conductivity of the nanocomposite paper. The FTIR study reveals the removal of non‐cellulosic components of plant fibers such as hemicelluloses, lignin, pectin, etc. during the chemical treatment. XRD analysis shows that the crystallinity of raw fiber increases from 56% to 63% after bleaching. The POM imaging of different samples also indicates an increase in the smoothness of the particle morphology, a decrease in particle size, and removal of lignin during the chemical treatment as suggested by the FTIR study. The composite paper comprising 5 and 10 wt% of MWCNT shows exceptionally high bulk conductivity of 1.56 and 6.27 S cm−1, respectively.

Role of Fe3+ doping vis-à-vis secondary phases on the electrical transport of LiTi2(PO4)3 solid electrolyte

Fast ion conducting solid-electrolytes, with diverse technological applications, have been studied critically in recent years. Among various prototype structures, NASICON structured materials are known for their comparatively high bulk conductivities, which could be further improved by selective substitution at cationic sites. Present work reports the effect of Fe3+ doping at the Ti4+ sites vis-à-vis secondary phases on the ionic conductivity of NASICON structured lithium titanium phosphate (LiTi2(PO4)3 or LTP) solid electrolyte. Li1+xTi2−xFex(PO4)3 (x = 0.0, 0.1 and 0.2) was synthesized using the solid-state reaction method. Crystal structure, morphology, chemical composition, and ionic conductivity were studied using room-temperature powder X-ray diffraction (p-XRD), field emission scanning (FESEM) and high-resolution transmission (HRTEM) electron microscopy, and temperature-dependent impedance spectroscopy. Very low bulk activation energies were found for all the samples, attributed to interstitial diffusion via a concerted migration. The room-temperature ionic conductivity initially increased upon Fe3+ doping (x = 0.1) and dropped subsequently (x = 0.2). The aberrant growth of electrolyte grains, associated gas pores, and cracks formed during sintering were successfully reduced by the LiTiOPO4 phase formation upon Fe doping, initially raising the grain boundary conductivity. However, doped samples also showed segregation of another secondary phase, Li2FeTi(PO4)3, whose larger weight fraction at x = 0.2 severely restricted the Li-ion migration resulting in sudden conductivity loss. These results suggest the need to optimise the microstructure, especially the amount of secondary phases, which contribute to the grain boundary resistance, affecting the ionic conductivity of the samples.

Acid-Base Chemistry Provides a Simple and Cost-Effective Route to New Redox-Active Ionic Liquids.

Redox-active ionic liquids (RAILs) hold great promise as high density electrochemical energy storage materials, but are hampered by high costs and low bulk conductivities. In this work, we introduce and electrochemically characterise novel redox-active protic ionic liquids (RAPILs) formed by acid-base neutralisation from cheap and plentiful starting materials. We also demonstrate a novel RAIL-in-IL solvent system for electrochemical characterisation of RAPILs, which enables efficient and cost-effective determination of redox potentials and screening for electrochemical reversibility. Of the redox-active ionic liquids tested in this work, only propylammonium 4-nitrophenylacetate demonstrates completely reversible electrochemistry and preservation of ionic character upon redox cycling under acidic or neutral conditions. Propylammonium 2,5-dihydroxyphenyl-carboxylate also demonstrates two reversible redox processes, but is unstable to oxidation at 0.27 V vs Ag (-0.14 V vs Fc), most likely forming an uncharged benzoquinone species. Using the lessons learned from this prototypical set of RAPILs, we propose design criteria to guide future experimental and computational work.

Highly conductive hexaazatrinaphthylene-based salphen organic frameworks with atomically dispersed dual-metal sites for efficient electrochemical oxygen evolution

The 2D conductive porous organic frameworks (POFs) with single metal sites are expected to be ideal electrocatalysts. However, developing POFs with multi-metal sites to boost their activities remains a formidable challenge. Herein, we report the synthesis of hexaazatrinaphthylene-based salphen organic framework (HATN-SOF) with two different coordination sites for atomically dispersion of nickel/iron ions. Due to the high loading active metal sites, the synergy between Ni/Fe ions, and the high bulk conductivity of 0.144 S/m, the bimetallic NiFe-HATN-SOF showed high electrochemical oxygen evolution activity with a low overpotential of 259 mV at 10 mA cm−2. The mass activity and turnover frequency value reach 1304 mA/mg and 0.193 s−1 respectively at an overpotential of 300 mV, which are more than 20-times larger than those of the monometallic HATN-SOFs and of the benchmark RuO2. The research offers a new platform for rational design of bio-inspired heterobinuclear electrocatalysts with customized microenvironments for oxygen electrocatalysis.

Magnetotelluric image of a hyper-extended and serpentinized rift system

Magnetotelluric (MT) data can image the Earth's electrical resistivity down to the mantle but are rarely used for investigation of offshore rifted margins. In such settings, the lower crust and upper mantle are altered by distinct tectono-thermal processes but often display similar seismic velocities and densities. By integrating resistivity models from MT data, we aim at resolving such ambiguity. Here, 3D inversion of long period, marine MT data (1 – 3000 s) is performed on 104 receivers located along two, ∼300 km long transects in the SW Barents Sea. The resolving power of MT data is assessed with synthetic tests in an archetypal rift system where ample crustal thickness variation occurs. The results highlight that our MT data sense the transition from necking to hyper-extended domain where the crust (<10 km) is not recovered by 3D inversion. In the Bjørnøya Basin – the northernmost member of a hyper-extended Cretaceous basin chain in the NE Atlantic – we combine seismic interpretation and MT inversion models to assign resistivity properties at two depth intervals: (1) 0.1-1 Ωm within Lower Cretaceous marine shales buried at 10-15 km depth (2) 1-10 Ωm within the uppermost mantle. Based on a fluid-rock model, we emphasize that seawater as a sole pore fluid phase is not conductive enough to explain such high bulk conductivities at both intervals. A 25% serpentinization of mantle rocks can account for a fivefold rise in salinity of the residual fluid and is compatible with bulk resistivity, density, and seismic velocities in the Bjørnøya Basin. Such high-salinity fluid can ascend and mix with seawater in pore spaces of the sediments, supporting our model of saline fluid circulation in hyper-extended basins. In conclusion, electrical resistivity models can disambiguate interpretation of deep structures in rifted margin by detecting saline fluids from partial serpentinization, intermixing with seawater in overlying marine sediments.

Evolution of Nanodomains and Formation of Self-Organized Structures during Local Switching in X-Cut LNOI

The features of nanodomain growth during local switching in X-cut lithium niobate on insulator (LNOI) were comprehensively studied using the biased tip of a scanning probe microscope. The obtained results were discussed in terms of the kinetic approach. The revealed differences in domain growth in bulk LN and LNOI were attributed to the higher bulk conductivity of LNOI. The obtained influence of humidity on the shape and growth of isolated domains was attributed to the water meniscus. Analysis of the transition between the “forward growth” and “sideways growth” stages was performed by switching to the stripe electrode. A sand-glass-shaped domain was formed due to growth in the opposite direction after the domain touched the electrode. Stable periodical domain structures down to 300 nm were created and characterized in LNOI. Highly ordered comb-like domains of various alternating lengths, including four- and eight-fold increase periods, were produced by performing biased tip scanning along the Y axis. The obtained knowledge is important for the future development of nanodomain engineering methods in monocrystalline ferroelectric thin films on insulators.

H2O-enhanced CO2 transport through a proton conducting ceramic- molten carbonate dual-phase membrane

High-temperature membranes for CO2 transport and separation has attracted significant interest from academia and industries due to their potential to mitigate the emissions of CO2 and ultimately global warming/climate change. In this study, we report a dual-phase CO2 membrane fabricated from a porous proton conducting BaZr0.8Y0.2O3-δ (BZY) matrix and eutectic mixture of Li2CO3–Na2CO3 (denoted as MC). The membrane exhibits a high CO2 permeation flux density in the range of 550–750 °C in both dry and wet conditions. Through microstructural optimization, a CO2 flux density as high as 0.34 mL ⋅ cm−2⋅ min−1 at 650 °C and 0.53 mL ⋅ cm−2⋅ min−1 at 750 °C have been achieved with an 0.8 mm thick BZY-MC membrane containing 52% porosity and 50%CO2–N2 feed gas. The high flux is attributed to synergistic effects of microstructure, MC loading and high bulk conductivity of BZY. In addition, we also demonstrate the positive effect of H2O in the permeate side on CO2 flux density and proposed a reasonable mechanism to explain the H2O-enhanced CO2 flux density. With 3% H2O-added into the sweeping gas, the membrane exhibits 30% CO2 flux density enhancement and good stability over 250 h at 650 °C.

Biocompatibility evaluation of encapsulated silver-based printed circuits for in-vitro long-term sensing devices

Metal-based inks, such as silver nanoparticle (AgNPs) dispersions, are standard solutions in printed electronics (PE) due to their high bulk conductivity, stability, and commercial availability. Conductive functional printed patterns have been exploited for several applications, such as (wearable) sensors, antennas, transistors, batteries. Recently, PE has also been widely investigated for biomedical and bioelectronic interfaces. In this case, the choice of biocompatible materials is crucial to ensure biological activities of the seeded cells. For instance, the release of Ag+ ions in the medium culture in in-vitro cultures, is known to induce cytotoxicity, in a dose-, size-, and time-dependent way, causing oxidative stress and eventually cellular death. Hence, an encapsulation step of the printed pattern is usually performed to reduce such risk, by inducing however additional limitations and complications on the design and production. This work investigates the biocompatibility of a commercial Aerosol Jet® Printed (AJ®P) AgNPs-based ink (Øavg,particle size = 35 nm, Ag content ~50 wt%) use to print conductive circuits for in-vitro bioelectrical sensing. Particularly, the ink was AJ® printed on the top of stereolithography (SLA) samples coated with Parylene-C, and further encapsulated with polydimethylsiloxane (PDMS).Cell viability assays were evaluated using both in adhesion and suspension cell type, such fibroblasts and B-Lymphoblastoid cell line respectively, at different time points from 7 days till 21 days to verify cellular activity and proliferation for long term usage. This work provides new insights concerning the use of encapsulated conductive AgNPs-based circuits for in-vitro long-term sensing devices.

Experimental investigations on nano-ferrite embedded nanocomposite polymer electrolytes for proton-conducting rechargeable batteries application

The present work is based on the influence of addition of BiNiFeO3 nanoparticles on the charge transport mechanism of PVA-NH4CH3COOpolymer gel electrolyte. Pure BiNiFeO3 nanoparticles and the gel membranes are synthesized by sol-gel and solution cast methods respectively. XRD spectrum of pure BiNiFeO3 confirms the nanometric dimension. FTIR studies reveals interaction and shifting in characteristics peaks of constituents. The impedance analysis shows at 0.4 wt% BiNiFeO3 embedded with electrolyte has higher bulk conductivity. Cyclic voltammetry analysis on the membranes shows better electrochemical stability i.e. ±4.68 V and confirms the availability of H+ ion (proton) in the system suggested proton-conducting batteries application.

The Role of Structural Features and System Relaxations on the Electrical Response of La1/2+1/2xLi1/2-1/2xTi1-XAlxO3 Perovskites

The all-solid-state batteries (ASSBs) using solid electrolytes are excellent candidates for the next generation of commercial devices for energy storage. Among these, the perovskite-type family of Li-ion conducting oxides Li3xLa2/3−xTiO3 (LLTO) is one of the most studied [1] and it is shown as the most promising option for solid electrolytes because of its high bulk conductivity (10−3 S·cm−1) [2], negligible electronic conductivity [3] high stability, wide electrochemical window (larger than 4 V) [4] and easy preparation. [5] However, there are still many challenges to be solved: (i) the high impedance associated with grain boundaries which reduce the overall lithium ionic conductivity below 10-5 S/cm at 298 K; (ii) and the instability of LLTO in direct contact with metal Li, [6],[7] or graphite electrodes.[8], [9],[10] In this contribution, we have focused on the substitution of B-site of LLTO perovskite, La1/2+1/2xLi1/2-1/2xTi1-xAlxO3 (0 ≤ x ≤ 1) studying the influence of vacancy distribution on percolative phenomena. Along this series, (1/2Li+ + Ti4+) cations were substituted by (1/2La3+ +Al3+), preserving both the charge balance and the nominal A-site vacancies (nA = 0). Accordingly, the main goal of this study is to confirm the influence of effective vacancies and their distribution, instead of nominal vacancies, on the Li conduction mechanism. The presence of order/segregation must influence the conductivity of these materials and by performing Broad band Electric Spectroscopy (BES), which is a powerful technique for unravelling the complexities of a polycrystalline ceramic, the analysis of the different contributions to the electric response of this complex materials can be achieved[11], [12].Indeed, here the aim is to study the correlation between structural features, determined by HRTEM/STEM, and relaxation phenomena characterizing the electric response of these perovskites by means of the BES. To better elucidate the interplay between structural features, conductivity and relaxation phenomena from the electric response of these materials, Density Functional Theory (DFT) and dynamic molecular modelling simulations studies are carried out.Taking all together, it is shown that the charge migration processes occurring along the different conductivity pathways for Li+ long range migration phenomena are very effective when in these perovskites: a) a sufficient density of charge carriers is present; and b) in the Ti4+ based BO6 backbone octahedra, Al3+ ions acts as a defect, thus enhancing the dynamics characterizing their relaxation modes. This latter effect is obviously dependent on the existence of an efficient coupling between the host medium relaxations of the inorganic network and the relaxation events characterizing the long range migration processes of lithium conductivity pathways.In conclusion, this study permits to shed light precisely into the conduction mechanism in Li3xLa2/3−xTiO3 –type perovskites. Acknowledgements This work has been supported by the European Union’s Horizon 2020 research and innovation program under grant agreement No 829145 (FETOPEN-VIDICAT) and by the Agencia Española de Investigación /Fondo Europeo de Desarrollo Regional (FEDER/UE) for funding the projects PID2019-106662RBC43 and C44. V. Di Noto thanks the University Carlos III of Madrid for the "Cátedras de Excelencia UC3M-Santander" (Chair of Excellence UC3M-Santander).

Fabrication and electrical conductivity of Lu2(Ti1-x Hf x )2O7 transparent ceramics prepared by spark plasma sintering

ABSTRACT Lu2(Ti1-x Hf x )2O7 (x = 0–0.5) transparent ceramics were fabricated by reactive spark plasma sintering using commercially available Lu2O3, TiO2 and HfO2 powders. Effect of Hf content x on the phase evolution, microstructure, density, transmittance and electrical conductivity of the resulting ceramics were investigated. Lu2(Ti1-x Hf x )2O7 transparent ceramic had a pyrochlore structure in the range of x = 0–0.3, while preserved a defect-fluorite structure at x = 0.4–0.5. The lattice parameter and theoretical density increased linearly with increasing Hf content x. The average grain size decreased at x = 0–0.3 and kept almost constant at x = 0.4–0.5. All the samples exhibited a dense microstructure and the highest in-line transmittance was 57% at 550 nm at x = 0. The highest bulk conductivity was 1.7 × 10−2 S m−1 at 1073 K for Lu2(Ti0.8Hf0.2)2O7, with an activation energy of 1.16 eV.

Phase evolution during reactive flash sintering of Li6.25Al0.25La3Zr2O12 starting from a chemically prepared powder

Reactive flash sintering (RFS) of a chemically prepared multiphase precursor powder was performed to fabricate Li6.25Al0.25La3Zr2O12 (Al-LLZO) ceramics. This approach allowed for obtaining single-phase dense samples in a remarkably short processing time of 30 s, at a furnace temperature of 600 °C, with an electric field of 50 V cm−1 and a current limit of 150 mA mm-2. The ceramics display high bulk conductivity of 0.18 mS cm−1 at room temperature. Furthermore, phase evolution is studied by in-situ X-ray diffraction during: i) conventional heating and ii) RFS under current rate mode. As expected, the intermediate phases progressively dissolved into the Al-LLZO matrix by conventional heating. On the other hand, RFS promoted the growth of the intermediate La2Zr2O7, an effect that was overcome by the thermally driven formation of Al-LLZO at higher temperatures. The observed different reaction pathway suggests that RFS can be used for stabilizing phases that are not thermodynamically favored upon conventional heating.

A time-filtering method for plasma simulation: High bulk conductivity

In this paper we aim to make possible the simulation of plasma - solid interaction in real insulating components using a set of first-principle partial differential equations. The high ratio between the conductivities of the many materials present in electrical components causes the associated numerical problem to become very stiff and this curtails the maximum allowed time step increase.To simulate some realistic components using sufficiently large time steps a filtering method is applied. A novel theoretical analysis has been developed showing that the filter allows the use of larger time steps without affecting the accuracy of the method. This analysis is backed by the results of a significant numerical experiment.

Al-doped Li7La3Zr2O12 garnet-type solid electrolytes for solid-state Li-Ion batteries

Cubic phase Li7La3Zr2O12 (LLZO) is a promising solid electrolyte for next-generation Li-ion batteries. In this work, the combustion sol–gel technique is used to prepare an Al-doped LLZO solid electrolyte. The crystal structure is investigated, and the cubic phase is confirmed. Densification properties were investigated using SEM and optical dilatometry. The densification of the Al-doped sample takes place in two stages through two different shrinkage rates. Using 0.25 mol Al-dopant 94% relative density is achieved at 1100 °C. The effect of Al-doping on electrochemical properties is investigated in detail using AC impedance spectroscopy. The result indicates that the optimum concentration of the Al dopant in this study is 0.25 mol and, exhibits a high bulk conductivity of 5.89 × 10–4 S cm−1 at 25 °C. Also, the grain boundary conductivity for the 0.25 mol Al-doped LLZO sintered at 1100 °C is improved by half an order of magnitude comparing to Al free sample. The effect of a secondary phase formation on the electrochemical response is identified using the distribution of relaxation times (DRT) method. The time constant responses for different resistive components are characterised as a function of frequency and capacitance and the values are then quantified using an equivalent circuit model.