Low-temperature Conductivity Research Articles

Electrical and gamma ray shielding properties of phospho-tellurite glasses doped with alkali and transition metal oxides

This article presents investigated results on physical, electrical and gamma radiation shielding properties of glasses of composition, (P2O5)0.25-(TeO2)0.5-x-(Na2O)0.1- (ZnO)0.15-(CoO)x (x= 0.10, 0.15, 0.20, 0.25, 030 and 0.35) were synthesized by melt quenching procedure. After confirming non-crystallinity, density was measured and found it to be decreased with increase of CoO concentration in the range 4.0370 gm/cm3 - 3.5673 gm/cm3. Molar volume, mean distance between TMIs, small polaron radius, oxygen packing density and field strength were estimated. Conductivity was measured in the temperature range 303K -663K. High temperature conductivity is found to be varied as per Mott’s (SPH) model. High temperature activation energy is found to be increased with CoO content. Low temperature conductivity variation has been analyzed using Mott’s (VRH) model. Gamma ray shielding parameters were evaluated using Phy-X/PSD software for the energy range 0.005 MeV-15 MeV. The mass and linear attenuation coefficients were found to decrease with CoO content and photon energy. Half and tenth value layers increased with increase of mole fractions of CoO. All the observed shielding parameters are superior to those reported previously for other glasses. The glass with x=0.10 is best suited for the utility of gamma shielding at low energy.

DFT based computational investigations of the physical properties of perovskites-structure SrXO3 (X = Si, Tb, Th) for optoelectronic and thermo-mechanical applications

Density Functional Theory (DFT) method is employed for investigating the structural, elastic, electronic, optical, and thermal properties of Perovskite structure SrXO3 (X = Si, Tb, and Th). The studied lattice parameters show good agreement with the previous theoretical and experimental results. The elastic stiffness constants, (Cij) of SrSiO3, SrTbO3, and SrThO3 satisfied the born stability criteria which confirm the mechanical stability of these phases. It is observed that when Tb or Th is replaced with Si, the brittleness behaviours of SrTbO3 or SrThO3 change to ductility, which improves its machinability for industrial applications. The investigation of anisotropic factors of SrSiO3, SrTbO3, and SrThO3 ensured that SrSiO3 is more anisotropic than SrTbO3 and SrThO3. By evaluating the electronic properties, it can be advantageous for applying the topological insulators (TI), solar cells, or PV (Photovoltaic) cell fabrication. Furthermore, the optical properties are studied and detail discussed with SrXO3 (X = Si, Tb, and Th). The reason of low Debye temperature (ΘD) and low minimum thermal conductivity (Kmin) has been perfectly explicated through the consideration of the mean atomic weight (M/n) of the compounds. Temperature-dependent of heat capacities (Cv, Cp) and linear thermal expansion coefficient (α) are also estimated using the quasi-harmonic Debye model and discussed. The SrTbO3 and SrThO3 compounds can be employed as potential thermal barrier coating (TBC) materials for high-temperature applications, according to the low values of Kmin, ΘD and α.

PVP/PEG polymer blend based electrolytes for quasi-solid-state dye-sensitized solar cells operating at low temperature

We investigated the performance of quasi-solid-state dye-sensitized solar cells (qs-DSSCs) employing Polyvinylpyrrolidone/Polyethylene glycol (PVP/PEG) blends over a wide temperature range. The photovoltaic performance of qs-DSSCs with conventional polymer electrolytes is very poor at low temperatures, mostly because of the significantly reduced ionic conductivity of the electrolyte. The PVP/PEG blend with a composition ratio of 20/80 exhibited low glass-transition temperature and high ionic conductivity, resulting in a power conversion efficiency (PCE) of 2.91% at a low temperature (−133 °C). This is 2.67 times higher than that of the device PCE (1.09%), with the most efficient and conventional gel-type polymer electrolyte. At ambient temperature, the qs-DSSC with PVP/PEG realized a device PCE of 6.13%, which is comparable to that of cells with conventional liquid electrolyte employing 3-methoxypropionitrile (6.36%) or a polymer electrolyte based on poly (vinylidene fluoride-co-hexafluoropropylene) (6.05%). In addition, the qs-DSSC with PVP/PEG exhibited excellent long-term stability during aging test, retaining approximately 88% of its initial PCE after 1000 h of light irradiation. The electrolyte developed in this study is not constrained by temperature factors and can be applied to solar cells that are viable for practical outdoor use (polar regions and space) with increased power output.

Formulating nickel metal organic decomposition ink with low sintering temperature and high conductivity for ink jet printing applications

Formulating nickel metal organic decomposition ink with low sintering temperature and high conductivity for ink jet printing applications

Physical and electrical properties of Sm2O3 doped Boro-Zinc-Vanadate glasses

Sm2O3 doped boro-zinc-vanadate glass systems were synthesised by following the melt quenching method. XRD patterns indicated largely non-crystalline nature with few nano-crystallites. Room temperature density was measured. Molar volume and various polaron parameters were estimated. Density and molar volume are found to vary non-linearly with samarium concentration. Conductivity has been measured by two probe technique for temperature range 303K - 573K. High temperature conductivity obeyed the small polaron hopping (SPH) theory. Activation energy for conduction in the temperature regime of small polaron theory is found to vary from 0.249 eV to 0.368 eV non-linearly with Sm2O3 concentration. The conductivity data at low temperature deviated has been looked into using Mott’s VRH model and the density of states at Fermi level were determined. Shimakawa’s multiphonon tunnelling model has also been applied to the low temperature conductivity and found linearity between logarithmic conductivity, ln(σ) and logarithmic temperature ln(T) as predicted by the model. The temperature exponent values obtained from Shimakawa’s model fit are found to be in good agreement with literature. Therefore, it is concluded that at low temperature, carrier multiphonon tunnelling is the charge transport mechanism in the present glasses.

Natural Convection in the Melting of Phase Change Materials in a Cylindrical Thermal Energy Storage System: Effects of Flow Arrangements of Heat Transfer Fluid and Associated Thermal Boundary Conditions

Abstract Latent thermal energy storage systems (LTESS) have received widespread attention due to their high energy density to store a significant amount of thermal energy in the form of latent heat into phase change materials (PCM) at a nearly constant melting temperature. The thermal efficiency of LTESS is usually limited by poor heat conduction in PCM but enhanced by the natural convection of molten PCM. The natural convection increases the uniformity of temperature by mixing in a PCM enclosure and therefore increases the heat transfer rates and accelerates the melting. While there is negligible natural convection, periodic reciprocation of heat transfer fluid (HTF) through the PCM enclosure has been demonstrated to increase the heat transfer rates to PCM by increasing the melt interface area and reducing temperature gradients across PCM compared to fixed-directional flow arrangements. The current study examines the effects of HTF flow direction on the strength and duration of natural convection in PCM in a vertical cylindrical shell-and-tube container. Gallium is used as the PCM because of its low melting temperature and high thermal conductivity, and water is used as the HTF. A 2-D axisymmetric numerical model developed in ANSYS Fluent was used for the study of the cylindrical LTESS. The aspect ratio of the cylindrical container is nearly 1, which allows the generation of natural convection currents of strong magnitude in molten PCM in the vertical orientation. The irregular melting front in the PCM is caused by both natural convection in molten PCM and thermal boundary conditions for different HTF flow arrangements. The temperature and melting front profiles of PCM with the reciprocating flow arrangement are compared to unidirectional flows in upward and downward directions. The influence of HTF operating parameters such as temperature, velocity, and reciprocation period on PCM melting is studied. Scale analysis is also applied to characterize the different melting regimes of PCM under different flow arrangements.

Electrochemical Science & Engineering Graduate Program at the University of California Irvine

The initiative to create an interdisciplinary program to train PhD (and in parallel terminal ME) graduate students in electrochemistry have been in circulation at University of California Irvine (UCI) since the Fall of 2018. Several “grass-root” meetings of faculty with sustained professional interests in the general interdisciplinary area of electrochemistry and electrochemical engineering involving faculty from UCI School of Physical Sciences (Chemistry and Physics & Astronomy) and Henry Samueli School of Engineering (Chemical & Biomolecular Engineering, Materials Science & Engineering, Mechanical & Aerospace Engineering) have taken place and lead to an internal formal proposal to create the program. This process was additionally catalyzed by the transformation of UCI Advanced Power & Energy Program into UCI Clean Energy Institute, to include National Fuel Cell Research Center and Horiba Institute for Mobility & Connectivity. This initiative was indeed halted for practically three years by the COVID pandemics and is being revisited just now in the Fall of 2022. The campus wide initiative Electrochemical Science & Engineering aims to support building a strong academic discipline to serve as a science and engineering backbone for decarbonization of technology and economy. The general research areas are (listed below) are being supported by a series of graduate classes: Electrochemistry & Electroanalytical Methods (Chemistry); Electrochemical Thermodynamics & ElectrochemicalSystems (MAE); Kinetics of Electrochemical Processes (CBE); Electrochemical Engineering (CBE); Electrochemical Energy Conversion & Storage (CBE) and Solid-State Electrochemistry (MSE) – all of which have been taught in a given, pre-arranged sequence as electives in correspondent departments with an substantially overlapping student audience during 2020/21 and 2021/2022 Academic Years. New technical electives in the areas of Bioelectrochemistry & Bioenergetics, Electrochemical Sensors & Biosensors and Electrochemical Water Treatment Technologies are being prepared for the 2022/223 Academic Year by newly recruited faculty. The lineup of the curriculum and the segmentation of it into specializations will be discussed. We will also address the creation of professional (termina) Master in Engineering (ME) graduate program.Research themes that will be covered by the program are practiced by some 17 faculty at UC: Electrochemical energy technologies, such as fuel cells, electrochemical sensors, electrolyzes, and batteries, use chemical change to produce electricity, or vice versa, and consist of catalytic electrodes and ion-conducting electrolytes. Ion transport between the electrolytes is often limited due to intrinsic properties of (often polymeric) ion-exchange membranes, or low-temperature conductivity of solid-state ionic materials. The next frontier in the science and technology of electrochemical interfacesis exploiting the unique opportunities offered by our emerging ability understand ionic and charge transfer interactions at nanoscale and to tailor both soft and solid-state materials structures to facilitate such interactions including in corrugated and confined structures. Electrocatalytic systems directly utilize electrical energy to perform redox reactions. The latter is essential to most chemical bond forming/breaking events and in energy storage and utilization reactions. Molecular electrocatalysis effort is focused on designing molecules with tailored active sites, predicted by computational chemistry, in order to achieve optimal energies in abundant metals. This further extends to bioelectrocatalysis by proteins and bioelectrochemistry of cells.

Author Correction: Enhanced low-temperature proton conductivity in hydrogen-intercalated brownmillerite oxide

Author Correction: Enhanced low-temperature proton conductivity in hydrogen-intercalated brownmillerite oxide

Tuning the anomalous Nernst and Hall effects with shifting the chemical potential in Fe-doped and Ni-doped Co3Sn2S2

Co3Sn2S2 is believed to be a magnetic Weyl semimetal. It displays large anomalous Hall, Nernst and thermal Hall effects with a remarkably large anomalous Hall angle. Here, we present a comprehensive study of how substituting Co by Fe or Ni affects the electrical and thermoelectric transport. We find that doping alters the amplitude of the anomalous transverse coefficients. The maximum decrease in the amplitude of the low-temperature anomalous Hall conductivity is twofold. Comparing our results with theoretical calculations of the Berry spectrum assuming a rigid shift of the Fermi level, we find that given the modest shift in the position of the chemical potential induced by doping, the experimentally observed variation occurs five times faster than expected. Doping affects the amplitude and the sign of the anomalous Nernst coefficient. Despite these drastic changes, the amplitude of the ratio at the Curie temperature remains close to , in agreement with the scaling relationship observed across many topological magnets.

Coexistence of Both Localized Electronic States and Electron Gas at Rutile TiO2 Surfaces.

Localized electron polarons formed through the coupling of excess electrons and ionic vibrations play a key role in the functionalities of materials. However, the mechanism of the coexistence of delocalized electrons and localized polarons remains underexplored. Here, the discovery of high-mobility 2D electron gas at the rutile TiO2 surfaces through argon ion irradiation induced oxygen vacancies is reported. Strikingly, the electron gas forms localized electronic states at lower temperatures, resulting in an abrupt metal-insulator transition. Moreover, it is found that the low-temperature conductivity in the insulating state is dominated by excess free electrons with a high mobility of ≈103 cm2 V-1 s-1 , whereas the carrier density is dramatically suppressed with decreasing temperature. Remarkably, it reveals that the application of an electric field can lead to a collapse of the localized states, resulting in a metallic state. These results reveal the strongly correlated/coupled nature between the localized electrons and high-mobility electrons and offer a new pathway to probe and harvest the exotic electron states at the complex oxide surfaces.

Numerical analysis for permafrost temperature field in the short term of permafrost subgrade filling

Purpose It is of great significance to study the influence of subgrade filling on permafrost temperature field in permafrost area for the smooth construction and safe operation of railway.Design/methodology/approach The paper builds up the model for the hydrothermal coupling calculation of permafrost using finite element software COMSOL to study how permafrost temperature field changes in the short term after subgrade filling, on which basis it proposes the method of calculation for the concave distortion of freezing front in the subgrade-covered area.Findings The results show that the freezing front below the subgrade center sinks due to the thermal effect of subgrade filling, which will trigger hydrothermal erosion in case of sufficient moisture inflows, leading to the thawing settlement or the cracking of the subgrade, etc. The heat output of soil will be hindered the most in case of July filling, in which case the sinking and the distortion of the freezing front is found to be the most severe, which the recovery of the permafrost temperature field, the slowest, constituting the most unfavorable working condition. The concave distortion of the freezing front in the subgrade area increases with the increase in temperature difference between the filler and ground surface, the subgrade height, the subgrade width and the volumetric thermal capacity of filler, while decreases with the increase of the thermal conductivity of filler. Therefore, the filler chose for engineering project shall be of small volumetric thermal capacity, low initial temperature and high thermal conductivity whenever possible.Originality/value The concave distortion of the freezing front under different working conditions at different times after filling can be calculated using the method proposed.

Proton and Oxygen-Ion Conductivity of the Pure and Lanthanide-Doped Hafnates with Pyrochlore Structure

In this work, a high-density ceramics Ln2Hf2O7 (Ln = La, Nd, Sm, Eu, Gd) were synthesized by mechanical activation followed by high-temperature synthesis at 1600°C (3–10 h) and their transport properties were compared with those of Ln2.1Hf1.9O6.95 (Ln = La, Nd, Sm, Eu) doped solid solutions. The total conductivity of ceramics was studied using impedance spectroscopy and dc four-probe method; for Ln2Hf2O7 (Ln = Sm, Eu), by determining the total conductivity as a function of oxygen partial pressure. The maximum oxygen-ion conductivity was observed for Gd2Hf2O7 (~1 × 10–3 S/cm at 700°C); it was shown to approach the conductivity of Gd2Zr2O7 (~2 × 10–3 S/cm at 700°C) for the first time. Thus, the gadolinium hafnate can be a promising material for further doping in order to obtain highly conductive electrolytes. Among pure rare-earth hafnates, the proton conductivity was reliably observed for Nd2Hf2O7 only; however, ac measurements detected low-temperature proton conductivity in the Gd2Hf2O7 up to 450°С as well. With a decrease in the lanthanide ionic radius, the oxygen-ion conductivity increased in the Ln2Hf2O7 (Ln = La, Nd, Sm, Gd) series. Although the conductivity of samarium hafnate is an order of magnitude lower than that of Gd2Hf2O7, it has a wide range of oxygen-ion conductivity (~10–18–1 atm at 700, 800°C); there is no contribution from hole conductivity in air, in contrast to Eu2Hf2O7. Among doped Ln2.1Hf1.9O6.95 pyrochlore solid solutions (Ln = La, Nd, Sm, Eu), the proton conductivity of ~8 × 10−5 S/cm at 700°C was shown in Ln2.1Hf1.9O6.95 (Ln = La, Nd). With a decrease in the lanthanide ionic radius, the proton conductivity disappeared; the oxygen-ion one, increased.

Low temperature electrical transport in thin carbon films deposited on SiO2/Si substrates by pulsed laser deposition

In this paper electrical transport studies are performed on thin carbon films deposited on SiO2/Si substrates by pulsed laser deposition (PLD) applying laser ablation of micro-crystalline graphite target. Experiments were carried out on 320 - 420 nm thick SiO2 on Si substrates as well as on hydrogenated diamond-like carbon (DLC) films deposited on SiO2/Si. Structural studies by means of XPS, SEM and Raman spectroscopy revealed that the films can be characterized as nano-sized carbon phases possessing different phase composition (i.e. the ratio sp3/sp2 hybridized carbon, etc.). The electrical conductivity/resistivity of the films was measured in the temperature range 10 K < T < 300 K. Four-contact Van der Pauw method as well as two contact schemes have been applied. Some films have low room temperature resistivity in the range ρ = (0.1–1.5)×10-3 Ω.·m and consist predominantly of sp2 hybridized carbon with Raman spectra, which resemble that of nano-sized graphene depending on the deposition conditions and substrates used. The thinnest only 0.5 nm layer deposited directly on SiO2 exhibits relatively low specific resistance (~10-3 Ω. m), which can be taken as an indication of good deposition conditions of graphene-like layers. The current flow mechanism was explored at temperatures from 300 K down to 10K. The temperature dependence reveals non-metallic behavior - the conductivity decreases at decreasing temperature as opposed to typical metal behaviour. A model of variable range hopping (VRH) mechanism is applied to explain the low temperature conductivity drawn from transport in nanocrystalline disordered systems.

Fast Na+ ion dynamics in the Nb5+ bearing NaSICON Na3+x−zNbzZr2−zSi2+xP1−xO12 as probed by 23Na NMR and conductivity spectroscopy

NaSICON-type (Na superionic conductor, Na1+yZr2SiyP3−yO12, 0 < y < 3) represent a class of fast Na+ ion conductors with bulk ion conductivities in the mS range near room temperature. Starting from Na3Zr2(SiO4)2(PO4), i.e., from y = 2, we investigated the change in ion transport parameter when x in Na3+xZr2Si2+xP1−xO12 is increased from 0 to 0.4 and Nb5+ is substituted for Zr4+ according to Na3+x−zNbzZr2−zSi2+xP1−xO12 (z = 0.04). The later might be beneficial also to change the transport properties in or near the grain boundary regions of our polycrystalline samples. To detect such changes, we used low-temperature conductivity and electric modulus spectroscopy to differentiate between the total and the bulk (intragrain) electrical responses. However, the main purpose of the present study is to corroborate the extraordinarily high bulk ionic conductivity of approximately 7.3 mS cm−1 (x = 0.4 and z = 0.04, room temperature) by diffusion-controlled 23Na NMR spin-lattice relaxation measurements. Indeed, such experiments directly sense the 23Na spin-fluctuations at the nuclear sites as a result of the fast intragrain motional processes. Both methods, nuclear and non-nuclear, point to a mean activation energy of 0.3 eV for Na+ exchange among the multiple sites in the NaSICON framework. In addition, NMR reveals local barriers characterized by activation energies as low as 0.1 eV. Altogether, from a dynamic point of view, Na3.36Nb0.04Zr1.96Si2.4P0.6O12 turned out to be indeed a very promising candidate for the breakneck development of Na-based all-solid-state battery applications.

Electrical transport studies in Na2O and Fe2O3 containing borate glasses

A new series of (X) Na2O.(0·5−x)Fe2O3.(0·5)B2O3 of sodium and iron oxides doped borate glasses were synthesised by melt quenching. The bulk density, structural and temperature dependent electrical properties of these glasses have been investigated. The density decreased with increase in Na2O content up to Na2O=0·2 and increased thereafter. The FTIR studies indicated the presence of BO3 and BO4 groups in the network and also has shown presence of minimum NBOs at x=0·2. These results are attributed to the significant structural modifications taking place in the glass network at Na2O=0·20. The dc electrical conductivity decreased with increase in Na2O content up to Na2O=0·20 and increased for further addition of Na2O. The activation energy has increased up to 0·2 mol% of Na2O and decreased thereafter. Based on these results, it is established that at x=0·20, a changeover of dc conduction mechanism predominantly from polaronic to ionic is taking place. Mott’s SPH, Mott’s VRH and Greave’s VRH models have been used to explain the high and low temperature conductivities.

Structural and thermal properties of Eu2Ga11Sn35

Clathrates have been reported to form in a variety of different structure types; however, inorganic clathrate-I materials with a low-cation concentration have yet to be investigated. Furthermore, tin-based compositions have been much less investigated as compared to silicon or germanium analogs. We report the temperature-dependent structural and thermal properties of single-crystal Eu2Ga11Sn35 revealing the effect of structure and composition on the thermal properties of this low-cation clathrate-I material. Specifically, low-temperature heat capacity, thermal conductivity, and synchrotron single-crystal x-ray diffraction reveal a departure from Debye-like behavior, a glass-like phonon mean-free path for this crystalline material, and a relatively large Grüneisen parameter due to the dominance of low-frequency Einstein modes. Our analyses indicate thermal properties that are a direct result of the structure and composition of this clathrate-I material.

Enhanced Oxide Ion Conductivity by Ta Doping of Ba3Nb1-xTaxMoO8.5.

Significant oxide ion conductivity has previously been reported for the Ba3M'M″O8.5 family (M' = Nb5+, V5+; M″ = Mo6+, W6+) of cation-deficient hexagonal perovskite derivatives. These systems exhibit considerable structural disorder and competitive occupation of two distinct oxygen positions (O3 site and O2 site), enabling two-dimensional (2D) ionic conductivity within the ab plane of the structure; higher occupation of the tetrahedral O3 site vs the octahedral O2 site is known to be a major factor that promotes oxide ion conductivity. Previous chemical doping studies have shown that substitution of small amounts of the M' or M″ ions can result in significant changes to both the structure and ionic conductivity. Here, we report on the electrical and structural properties of the Ba3Nb1-xTaxMoO8.5 series (x = 0.00, 0.025, 0.050, 0.100). AC impedance measurements show that substitution of Nb5+ with Ta5+ leads to a significant increase in low-temperature (<500 °C) conductivity for x = 0.1. Analysis of neutron and X-ray diffraction (XRD) data confirms that there is a decrease in the M1O4/M1O6 ratio upon increasing x from 0 to 0.1 in Ba3Nb1-xTaxMoO8.5, which would usually coincide with a lowering in the conductivity. However, neutron diffraction results show that Ta doping causes an increase in the oxide ion conductivity as a result of longer M1-O3 bonds and increased polyhedral distortion.

Low-temperature radiation-induced conductivity of polystyrene under the action of low-energy electrons

A technique has been developed and, for the first time, sufficiently complete data on the radiation-induced conductivity (RIC) of polystyrene (PS) at a temperature of 79 K, close to the boiling point of liquid nitrogen (77 K). RIC has been studied under pulsed and continuous exposure to electrons with an energy of 50 keV. It is shown that the RIC of PS at a temperature of 79 K, as well as at room temperature, determined by the sum of two components: prompt and delayed. Both components at 79 K are much smaller than at 298 K. The total signal falls off by a factor of 40, while the delayed component falls off by a factor of almost 200, and the prompt component dominant in the RIC signal. The possibility of the occurrence of electrostatic discharges (ESD) in PS with decreasing temperature was studied. It has been shown that PS, which is capable of resisting the occurrence of ESD at room temperature, at 79 K passes into the category of materials in which ESD is possible. Keywords: electron radiation, radiation-induced conductivity, polystyrene, low temperatures, electrification.

Heat transport of the kagome Heisenberg quantum spin liquid candidate YCu3(OH)6.5Br2.5 : Localized magnetic excitations and a putative spin gap

The spin-1/2 kagom\'{e} Heisenberg antiferromagnet is generally accepted as one of the most promising two-dimensional models to realize a quantum spin liquid state. Previous experimental efforts were almost exclusively on only one archetypal material, the herbertsmithite ZnCu$_3$(OH)$_6$Cl$_2$, which unfortunately suffers from the notorious orphan spins problem caused by magnetic disorders. Here we turn to YCu$_3$(OH)$_{6.5}$Br$_{2.5}$, recently recognized as another host of a globally undistorted kagom\'{e} Cu$^{2+}$ lattice free from the orphan spins, thus a more feasible system for studying the intrinsic kagom\'{e} quantum spin liquid physics. Our high-resolution low-temperature thermal conductivity measurements yield a vanishing small residual linear term of $\kappa/T$ ($T\rightarrow 0$), and thus clearly rule out itinerant gapless fermionic excitations. Unusual scattering of phonons grows exponentially with temperature, suggesting thermally activated phonon-spin scattering and hence a gapped magnetic excitation, consistent with a $\mathbb{Z}_2$ quantum spin liquid ground state. Additionally, the analysis of magnetic field impact on the thermal conductivity reveals a field closing of the spin gap, while the excitations remain localized.

Enhanced low-temperature proton conductivity in hydrogen-intercalated brownmillerite oxide

Enhanced low-temperature proton conductivity in hydrogen-intercalated brownmillerite oxide