Highest Total Conductivity Research Articles

Influence of AlPO4 Impurity on the Electrochemical Properties of NASICON‐Type Li1.5Al0.5Ti1.5(PO4)3 Solid Electrolyte

AbstractDensification of ceramic electrolytes is a key enabler in producing electrolyte pellets for solid‐state batteries. This requires understanding the correlation between the starting grain size of electrolytes, chemical phase evolution and degree of compaction which determine ion conductivity and chemical stability of solid electrolytes. In our work we were able to optimize the densification process of LATP at 700 °C with a high total ionic conductivity of 3.45×10−4 S cm−1 after hot pressing, balancing pristine LATP crystallite size and AlPO4 impurity formation. By combining several techniques such as in situ heating X‐ray diffraction (XRD), scanning electron microscopy (SEM) and nuclear magnetic resonance (NMR), we explored the formation mechanism of AlPO4 during the synthesis process of NASICON‐type Li1.5Al0.5Ti1.5(PO4)3 (LATP) electrolyte and we showed the effects of the annealing temperature on the crystal size of the material. Density functional theory (DFT) calculations on the chemical stability of the electrolyte imply a metastable behaviour of LATP furtherly enhanced by particle nano‐structuring at high temperature. Our results point to facile manufacturing of ceramic electrolytes towards energy dense and safe solid‐state battery technology.

Effect of Ni non-stoichiometry on the structural, thermal and conductivity properties of Nd2Ni1-xO4+δ

Neodymium nickelates Nd2Ni1-xO4+δ with Ni non-stoichiometry, varied in a wide x range of 0.0–0.08, are synthesized for the first time, and their properties are studied depending on the Ni content. The limit of Ni deficiency is found to reach 6%. According to the XRD data, the materials of the Nd2Ni1-xO4+δ series are single-phase in the range of x from 0.0 to 0.06 and exhibit an orthorhombic structure with a Fmmm space group. Results of the TGA-DSC studies shows that the temperature of the Fmmm – I4/mmm phase transition changes insignificantly (up to ∼5 °C), thus does not depend on Ni non-stoichiometry. The Raman scattering studies reveal that at low Ni deficiency the Raman spectra are typical for the Ni-stoichimetric oxidized (δ ≈ 0.2) Nd2NiO4+δ. While at the limiting value of x equal to 0.06, the lattice disorder and [NiO6] octahedral distortions reach a maximum feasibility with NiO1 vibrations getting involved into Raman scattering. The highest total conductivity (101 S/cm at the maximum) is observed for the sample with x = 0.02, which shows a more pronounced second-order overtone at 800–930 cm−1 in Raman scattering. This material can be recommended for further studies and possible electrochemical applications as the most prospective in the series due to its superior electrical properties.

Environmental quality and ecotoxicity of sediments from the lower Salado River basin (Santa Fe, Argentina) on amphibian larvae

The lower Salado River basin receive agricultural, industrial and domestic waste water. So, the aim was to evaluate the quality of three sampling sites that belong to the Salado River basin (S1: Cululú stream; S2: Salado River, at Esperanza City, S3: Salado River at Santo Tomé City) based on physicochemical parameters, metals and pesticides analyses and ecotoxicity on Rhinella arenarum larvae. R. arenarum larvae (Gosner Stage -GS- 25) were chronically exposed (504h) to complex matrixes of surface water and sediment samples of each site for the determination of the survival rate. Biomarkers of oxidative stress, neurotoxicity and genotoxicity were analyzed in R. arenarum larvae (GS. 25) after exposure (96h) to the complex matrix of water and sediment. The water quality index showed a marginal quality for all sites, influenced mainly by low dissolved oxygen, high total suspended solid, phosphate, nitrite, conductivity, Pb, Cr and Cu levels. Metal concentrations were higher in sediment than in water samples (˜34-35000 times). In total, thirty different pesticides were detected in all water and sediment samples, S1 presented the greatest variety (26). Glyphosate and AMPA were detected in sediments from all sites, being higher in S3. N,N-Diethyl-meta-toluamide (DEET) and atrazine were detected in all water samples. Greatest mortality was observed in larvae exposed to samples from S1 from 288h (43.3%), reaching a maximum value of 50% at 408h. Oxidative stress and genotoxicity were observed in larvae exposed to S1 and S3 matrix samples. Neurotoxicity was observed in larvae exposed to all matrix samples. The integrated biomarker response index showed that larvae exposed to S1 and S3 were the most affected. According to the physicochemical data and the ecotoxicity assessment, this important river basin is significantly degraded and may represent a risk to aquatic biota, especially for R. arenarum larvae.

LSGMCF dense diffusion barrier preparation and electrical characteristics for limiting current oxygen sensor

La0.8Sr0.2(Ga0.8Mg0.2)1-x(Cr0.4Fe0.6)xO3-δ(LSGMCF, x = 0.1, 0.3, 0.5, 0.7 and 0.9) and La0.8Sr0.2Ga0.8Mg0.2(LSGM) were synthesized by solid-state reaction with La2O3, SrCO3, Ga2O3, MgO, Cr2O3 and Fe2O3 as raw materials. By characterizing the phase analysis and micro-structure of LSGMCF, it was found that Cr and Fe dissolved in the main crystalline phase LSGM in a wide range. The effects of Cr and Fe concentrations on the electronic and total conductivity of LSGMCF were analyzed by Hebb-Wagner and Linear Sweep Voltammetry methods. The results show that when x = 0.9, it has better electronic conductivity and the highest total conductivity. LSGMCF(x = 0.9) and LSGM were prepared into limiting current oxygen sensor by co-pressing and co-sintering technique, and its sensing characteristics were studied. The oxygen sensor exhibits a limiting current in the range of 0–7% oxygen concentration at 730–790 °C. The limiting current is directly proportional to the oxygen concentration, indicating that it shows good sensing characteristics at different temperatures. In addition, its sensing performance has excellent stability between 0 -42h.

A‐site acceptor‐doping strategy to enhance oxygen transport in sodium–bismuth–titanate perovskite

AbstractSodium–bismuth–titanate (NBT) has recently been shown to contain high levels of oxide ion conductivity. Here we report the effect of A‐site monovalent ions, M+ = K+ and Li+, on the electrical conductivity of NBT. The partial replacement of Bi3+ with monovalent ions improved the ionic conductivity by over one order of magnitude without an apparent change of the conduction mechanism, which is attributed to an increase in the oxygen vacancy concentration based on an acceptor‐doping approach. The 18O tracer‐diffusion coefficient (D*) determined by the isotope exchange depth profile method in combination with secondary ion mass spectrometry confirmed that oxygen ions are the main charge carriers in the system. Among these acceptor‐doped samples, 4% Li doping provides the highest total conductivity, leading to a further discussion of doping strategies for NBT‐based materials to enhance the electrical behavior, is discussed. Comparisons with other oxide‐ion conductors and an oxygen‐vacancy diffusivity limit model in perovskite lattice suggested that the doped NBT‐based materials might already have achieved the optimization of the ionic conductivity.

Li-stuffed garnet electrolytes: structure, ionic conductivity, chemical stability, interface, and applications

Current lithium-ion batteries have been widely used in portable electronic devices, electric vehicles, and peak power demand. However, the organic liquid electrolytes used in the lithium-ion battery are flammable and not stable in contact with elemental lithium and at a higher voltage. To eliminate the safety and instability issues, solid-state (ceramic) electrolytes have attracted enormous interest worldwide, owing to their thermal and high voltage stability. Among all the solid-state electrolytes known today, the Li-stuffed garnet is one of the most promising electrolytes due to its physical and chemical properties such as high total Li-ion conductivity at room temperature, chemical stability with elemental lithium and high voltage lithium cathodes, and high electrochemical stability window (6 V vs. Li+/Li). In this short review, we provide an overview of Li-stuffed garnet electrolytes with a focus on their structure, ionic conductivity, transport mechanism, chemical stability, and battery applications.

Praseodymium Orthoniobate and Praseodymium Substituted Lanthanum Orthoniobate: Electrical and Structural Properties.

In this paper, the structural properties and the electrical conductivity of La1−xPrxNbO4+δ (x = 0.00, 0.05, 0.1, 0.15, 0.2, 0.3) and PrNbO4+δ are presented and discussed. All synthesized samples crystallized in a monoclinic structure with similar thermal expansion coefficients. The phase transition temperature between the monoclinic and tetragonal structure increases with increasing praseodymium content from 500 °C for undoped LaNbO4+δ to 700 °C for PrNbO4+δ. Thermogravimetry, along with X-ray photoelectron spectroscopy, confirmed a mixed 3+/4+ oxidation state of praseodymium. All studied materials, in humid air, exhibited mixed protonic, oxygen ionic and hole conductivity. The highest total conductivity was measured in dry air at 700 °C for PrNbO4+δ, and its value was 1.4 × 10−3 S/cm.

Effect of Two Different ZnO Addition Strategies on the Sinterability and Conductivity of the BaZr0.4Ce0.4Y0.2O3−δ Proton-Conducting Ceramic Electrolyte

A comparative study has been made to relate the effect of different addition strategies for the sintering aid of ZnO (∼1 wt %) on the performance of the BaZr0.4Ce0.4Y0.2O3−δ (BZCY442) electrolyte in order to improve the sinterability and conductivity of this material more efficiently. Two samples, Zn-doped BaCe0.4Zr0.4Y0.15Zn0.05O3−δ (BZCYZn, internal doping) and BZCY–ZnO (BZCY442 mixed with ZnO, external addition), were synthesized. The BZCYZn crystallized at a single phase after sintering at 1350 °C, and the segregation of Y2O3 was observed in BZCY–ZnO in the same conditions. The relative densities of the BZCYZn and BZCY–ZnO samples sintered at 1350 °C for 5 h were 98 and 94%, respectively. The high total conductivity in BZCYZn benefited from the low barrier height at the grain boundary core determined by the Mott–Schottky space charge layer model, which was 0.15 V for BZCYZn and 0.26 V for BZCY–ZnO. A cell with BZCYZn as the electrolyte generated a power density of 414.5 mW cm–2 at 700 °C. The total ionic transport number of BZCYZn was determined to be ∼0.90 at 600 °C under fuel cell conditions.

Chronological changes in soil biogeochemical properties of the glacier foreland of Midtre Lovénbreen, Svalbard, attributed to soil-forming factors

Glacier forelands provide an excellent opportunity to investigate vegetation succession and soil development along the chronosequence; however, there are few studies on soil biogeochemical changes from environmental factors, aside from time. This study aimed to investigate soil development and biogeochemical changes in the glacier foreland of Midtre Lovénbreen, Svalbard, by considering various factors, including time. Eighteen vegetation and soil variables were measured at 38 different sampling sites of varying soil age, depth, and glacio-fluvial activity. Soil organic matter (SOM) was quantitatively measured, and the compositional changes in SOM were determined following size-density fractionation. In the topsoil, the soil organic carbon (SOC) and total nitrogen (N) content was found to increase along the soil chronosequence and were highly correlated with vegetation-associated variables. These findings suggest that plant-derived material was the main driver of the light fraction of SOM accumulation in the topsoil. The heavy fractions of SOM were composed of microbially transformed organic compounds, eventually contributing to SOM stabilization within short 90-yr deglaciation under harsh climatic conditions. In addition to time, the soil vertical profiles showed that other environmental parameters, also affected the soil biogeochemical properties. The high total phosphorous (P) content and electrical conductivity in the topsoil were attributed to unweathered subglacial materials and a considerable amount of inorganic ions from subglacial meltwater. The high P and magnesium content in the subsoil were attributed to parent materials, while the high sodium and potassium content in the surface soil were a result of sea-salt deposition. Glacio-fluvial runoff hampered ecosystem development by inhibiting vegetation development and SOM accumulation. This study emphasizes the importance of considering various soil-forming factors, including parent/subglacial materials, aeolian deposition, and glacio-fluvial runoff, as well as soil age, to obtain a comprehensive understanding of the ecosystem development in glacier forelands.

Effect of sintering under CO+N2/H2 and CO2+air atmospheres on the physicochemical features of a commercial nano-YSZ

Given the need to process anodes and composites based on nano-YSZ in reducing or in air containing additional CO2 atmospheres for the fabrication of solid oxide fuel cells (SOFCs), and solid oxide electrolysis cells (SOECs), we have studied the effect of the exposure to CO+N2/H2 or CO2+air mixtures during sintering of YSZ green pellets, prepared from commercial nanopowders, on their structure, microstructure, chemical composition and their electrical properties. The reduced sample shows Raman bands at 1298 and 1605 cm−1 that are assigned to the D and G bands of carbon, respectively. The bands intensity ratio ID/IG indicates a larger content of disordered carbon. X-ray photoelectron spectroscopy (XPS) shows that C is present in the reduced samples as reduced carbon. However, the samples sintered in CO2+air present C as carbonate-type. Impedance spectroscopy reveals that the highest total conductivity is for the reduced samples in the whole range of studied temperatures. In addition, sintering in CO2+air causes a detrimental effect on the grain boundary conductivity and therefore, on the total electrical conductivity of YSZ. It can be due to the presence of impurities such as carbonates and oxidised or even, polymerised carbonaceous species located at those areas.

Evaluation of stability and functionality of BaCe1\u2212xInxO3\u2212\u03b4 electrolyte in a wider range of indium concentration

The properties of BaCe1−xInxO3−δ (x = 0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, and 0.40) as proton conducting electrolyte are examined. The dense electrolyte is formed after sintering at 1300 °C for 5 h in air. The samples with In content ⩾ 25 mol% contain In2O3 as a secondary phase. The highest total conductivity is around 5×10−3 S/cm for BaCe0.75In0.25O3−δ in the wet hydrogen atmosphere at 700 °C. After exposure to pure CO2 atmosphere at 700 °C for 5 h, the concentrations of at least 15 mol% In can completely suppress degradation of the electrolyte. The power density of Ni-BaCe0.75In0.25O3−δ/BaCe0.75In0.25O3−δ/LSCF-BaCe0.75In0.25O3−δ fuel cell tested in wet hydrogen atmosphere reaches 264 mW/cm2 at 700 °C. This result is an indication of stability and functionality of this electrolyte and its versatility in respect to type of fuel and performing environment.

Effect of Phase Ratio on Hydrogen Separation of Dual‐phase Membrane Reactors

AbstractThree dual‐phase MIEC membranes (100 – x) wt % Ce0.8Sm0.2O1.9 (SDC) – x wt % Sr0.92Ti0.5Fe0.5O3–δ (STF) (x = 30, 40, 50) were prepared by a one‐pot solid state reaction to explore the effect of phase ratio of dual‐phase membranes on the hydrogen separation performance of oxygen‐permeable membrane reactors. Single‐phase STF was synthesized by the same method for comparison. The grains of the two phases in the three dual‐phase membranes are uniformly and continuously distributed forming the three‐dimensional connected networks. Dual‐phase membranes have higher total conductivity than that of STF under simulated working atmospheres, and the total conductivity decreases with the increase of STF content. Under various test conditions, the hydrogen separation rate of the dual‐phase membranes is higher than that of the STF membrane.

Ionic Conductivity of Ce0.91Ca0.09O2 as an Electrolyte for Intermediate Temperature Solid Oxide Fuel Cells

The search for new cost-effective electrolyte materials for IT-SOFC towards its mass scale commercialization has gained momentum in recent years. The Ca- doped ceria having composition Ce0.91Ca0.09O2 was prepared using the facile conventional solid-state method. The structural and electrical properties of low sintered ceramic samples have been characterized by X-ray diffraction (XRD), UV–VIS diffuse reflectance spectroscopy (DRS) and A.C. impedance technique respectively. The oxide ion conductivity was measured between the temperatures 573 K−973 K in air. The obtained results showed that total conductivity is mainly dependent on the grain boundary effect. The nanocrystalline Ce0.91Ca0.09O2 exhibited the high total ionic conductivity of 7.36  103 S cm1 at 973 K with a lower activation energy of 0.96 eV. The obtained results highlight the use of cost-effective dopant in ceria lattice to develop commercially viable electrolyte materials for IT-SOFC.

Multiple Effects Promoting the Thermoelectric Performance of SnTe by Alloying with CuSbTe2 and CuBiTe2.

In a SnTe-based thermoelectric material, the naturally high hole concentration caused by cation vacancies and high total thermal conductivity seriously hinder its thermoelectric performance. A recent work shows that alloying SnTe with other compounds from the I-V-VI2 family (I = Ag, Na; V = Sb, Bi; VI = Te) can be considered an effective strategy to boost the figure of merit efficiently via the synergy of manipulating hole concentration and lowering lattice thermal conductivity. Herein, we present a markedly enhanced thermoelectric performance in p-type SnTe through CuPnTe2 (Pn = Sb, Bi) alloying. Moreover, we found that the alloying with both CuSbTe2 and CuBiTe2 can facilitate the valence band convergence of SnTe, but their relative influence is different. Interestingly, compared to CuBiTe2, alloying with CuSbTe2 increases the carrier concentration of SnTe, which suppresses the bipolar effect. Ultimately, under the positive effect of valence band convergence, increased vacancy concentration, and decreased lattice thermal conductivity, compounds with a nominal composition of (SnTe)0.90(CuSbTe2)0.10 attains a peak zT of ∼1.26 at 823 K. In contrast, the thermoelectric performance of (SnTe)1-x(CuBiTe2)x is restricted by the reduced carrier concentration and diminished band gap, showing only a humble maximum zT value of ∼0.91 at 823 K in the sample with a nominal composition of (SnTe)0.96(CuBiTe2)0.04. These results demonstrate the multiple effects on thermoelectric transport during the formation of complex solid solutions.

Transport and interface characteristics of Te-doped NASICON solid electrolyte Li1.3Al0.3Ti1.7(PO4)3

Te-doped NASICON-type Li1.3Al0.3Ti1.7(PO4)3 (LATP) electrolyte materials were prepared by ball milling-assisted solid state method. The structural, morphological, and transport properties of samples were analyzed through X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscope, energy dispersive X-Ray spectroscopy, electrochemical impedance spectroscopy, and DC polarization to determine optimal doping concentration. High total ionic conductivity of 7.03 × 10−4 S cm−1 and negligible electronic conductivity of 7.64 × 10−9 S cm−1 were obtained at room temperature for Li1.3Al0.3Te0.03Ti1.67(PO4)3 electrolyte. Interface characteristics analysis of electrolyte materials with Li electrode showed that voltage profile of Li/Li1.3Al0.3Te0.03Ti1.67(PO4)3/Li cell remained stable after 300 h of cycling with current density of 0.02 mA cm−2. Good cyclic stability at different temperatures was also demonstrated, with doped electrolyte presenting better interface stability than pure LATP. These results suggest that Te-doped LATP materials can be used as alternative solid electrolyte for all solid-state lithium-ion batteries.

Lightweight graphene encapsulated with polyaniline for excellent electromagnetic shielding performance in X-band (8.2–12.4 GHz)

Polyaniline (PANI) and its nanocomposites with graphene have been synthesized using simple chemistry based method and are utilized to mitigate the problem of electromagnetic pollutions in high-frequency range (X-band: 8.2–12.4 GHz) of the microwave region. The PANI/graphene nanocomposites showed total shielding effectiveness as high as 64 dB with 8 wt% loading of graphene in PANI. The EMI shielding effectiveness via absorption for all the samples dominates over the reflective part due to high dielectric losses in bulk of sample. The enhancement in shielding effectiveness properties are occurred due to strong polarization, charge propagation and formation of conducting pathways due to encapsulation of graphene in PANI. Moreover, the high dielectric losses (ɛ″ ≈ 35–175) and total ac conductivities (σm ≈ 11–102 S/m) contribute in enhanced shielding effectiveness. The very high values of shielding effectiveness for these samples make them suitable materials for industrial as well as defense/aerospace applications.

FABRICATION AND ELECTROCHEMICAL PERFORMANCE OF LiFePO4/Ga-LLZO/Li ALL-SOLID-STATE LITHIUM BUTTON CELL

An all-solid-state Lithium button cell with Ga-doped Li7La3Zr2O12 (Ga-LLZO) as solid electrolyte, LiFePO4-based as cathode, and Li metal as anode has been successfully fabricated and characterized. The solid electrolyte was first optimized to obtain a high total conductivity. Different compositions of Li7-3xGaxLa3Zr2O12, where x =0, 0.1, 0.2, and 0.3. Li7La3Zr2O12 (LLZO) were synthesized using solid-state reaction and were characterized for its structural, morphological, electrical conductivity properties. XRD patterns of all sintered samples showed that all of the major peaks can be indexed to a cubic-phased garnet LLZO. SEM images revealed a densified sintered samples with relative densities of about 90% for all samples. Among the different studied compositions, the Ga-doped LLZO with x = 0.1 achieved the highest total conductivity of about 2.03 x 10-4 Scm-1 at 25oC, with an activation energy of 0.31 eV. From this solid electrolyte, an all-solid-state Lithium battery, 2032 button cell, was fabricated using LiFePO4-based cathode and Lithium metal as the anode. Charging and discharging characteristics were performed at 1C, 0.5C, and 0.2C rates. The results showed a good retention of coloumbic efficiency even after 50 cycles of charge and discharge. The capacity retention is about 15-20% after 50 cycles. The best performance of the coin cell battery revealed an initial specific discharging capacity of about 140 mAh/g using C/5 rate.

Assessment of processing route on the performance of ceria‐based composites

Gd-doped ceria (GDC)-based composites, including a eutectic mixture of lithium and sodium carbonate (NLC) as second phase, were prepared using several processing routes, namely chemical synthesis, co-firing of both phases, or impregnation of a presintered porous matrix. LiAlO2-based composites were also prepared and used as reference. The structural, microstructural, and electrical properties (impedance spectroscopy in air, up to 700°C) of these materials were assessed in detail. A limited set of compositions was also used in measurements of total electrical conductivity at different oxygen partial pressures (from 0.21 to <10−25 atm), in the 600°C to 700°C range. The results obtained confirmed the enormous impact of the processing route on the percolation of the ceramic phase. In the exploited range of operating conditions, GDC-NLC composites prepared by infiltration of molten carbonates within a mechanically robust ceramic matrix exhibit a high total ionic conductivity strongly influenced by the contribution of the molten salt while the ceramic phase is decisive in the appearance of a significant component of electronic conductivity under reducing conditions.

Effect of sintering temperature on the microstructure and conductivity of Na0.54Bi0.46Ti0.99Mg0.01O3-δ

The present work examines the effect of sintering temperature on the phase formation and the conductivity of Na0.54Bi0.46Ti0.99Mg0.01O3-δ. The formation of the secondary phase and the poor grain boundary conductivity are a few major concerns in this recently developed material. Polycrystalline bulk specimens are fabricated through conventional pressureless sintering at different temperatures of 930 °C, 950 °C, 1000 °C, and 1050 °C for 2 h. A single rhombohedral perovskite phase is detected in the XRD profiles collected on all the sintered samples. However, the SEM micrographs reveal the existence of impurity phase in all the tested samples with the amount increasing considerably with the increase in temperature. The local elemental analysis of the impurity phase suggests the presence of non-stoichiometric Na2xTi2-xMgxO4 compound. However, the chemical composition of this compound varies across different specimens. The samples sintered at 950 °C exhibit the maximum bulk and grain boundary conductivities of 13.3 mS.cm−1 and 3.6 mS.cm−1, respectively, at 600 °C. A lower magnitude of both the conductivities is observed on sintering the samples at higher temperatures. The activation energy for bulk ionic conduction also decreases from 0.67 eV to 0.48 eV with the sintering temperature supporting the conjecture that higher Mg2+ amount is dissolved in the perovskite phase present in the samples sintered at 950 °C. The higher total conductivity in the samples sintered at 950 °C is attributed to the formation of comparatively less amount of Mg-rich impurity phase. Even though 950 °C appears to be an optimum sintering temperature, the grain boundaries of the samples continue to be resistive. At 600 °C, the grain boundary conductivity is less than one-third of the bulk conductivity. As a result, grain boundaries contribute a significant portion of the total resistivity offered by the Na0.54Bi0.46Ti0.99Mg0.01O3-δ samples.

Electrical properties of yttria-stabilised hafnia ceramics.

Cubic, yttria-stabilised hafnia, YSH, ceramics of general formula, YxHf1-xO2-x/2: x = 0.15, 0.30 and 0.45 were sintered at 1650-1750 °C and characterised by impedance spectroscopy. All three compositions are primarily oxide ion conductors with a small amount of p-type conductivity that depends on atmospheric conditions and appears to increase with x. The electronic conductivity is attributed to hole location on under-bonded oxide ions and the absorption of oxygen molecules by oxygen vacancies, both of which occur on substitution of Hf4+ by Y3+. Composition x = 0.15 has the highest total conductivity and shows curvature in the Arrhenius plot at high temperatures, similar to that of the most conductive yttria-stabilised zirconia.