Increasing Ru Content Research Articles

Influence of cationic vacancy diffusion on the aging behavior of low-temperature SrCo1-xRuxO3 thermosensitive ceramics

The thermosensitive ceramics of negative temperature coefficient (NTC), SrCo1-xRuxO3 (0 ≤ x ≤ 0.8), were synthesized using the solid-phase method. The research systematically explored the phase structure, microstructure, elemental chemical states, electrical properties, and aging performance. X-ray diffraction (XRD) data indicates that with the increase of Ru content, the lattice parameter increases. Scanning electron microscopy (SEM) images reveal a dense and uniform microstructure. X-ray photoelectron spectroscopy (XPS) data indicates the presence of Co2+/Co3+ and Ru4+/Ru5+ ion pairs. Resistive temperature data indicates its potential use as a low-temperature thermosensitive resistance material in the range of 2–300 K. Fitting the resistance-temperature curve using the thermally activated band conduction model and Mott's 3D variable range hopping model. Proposed the Ru–O2--Co hopping model, elucidating the hole hopping transport mechanism in NTC ceramics. Impedance spectroscopy analysis indicates that grain boundary resistance dominates the overall resistance of the sample. After aging at 77 K for 864 h, the maximum aging drift rate of the ceramic material is 1.55 %. Proposed a novel cationic vacancy diffusion model to explain aging phenomena, offering a new perspective for designing high-stability low-temperature NTC thermistors.

Selectivity of Mn rich Ru Mn O phases in parallel oxygen and chlorine evolution

Single phase Mn rich RuxMn1-x O2 conforming to a highly disordered γ MnO2 with pyrolusite-like blocks dominating in the structure were prepared in the low Ru content range (0.15 ≥ x ≥ 0.30). All synthesized materials were electrochemically active in oxygen and chlorine evolution in acidic media with variable chloride content. The total anodic activity increased with increasing Ru content in the structure as well as with increasing concentration of chlorides in the solution. The selectivity towards oxygen evolution reaction was predominant for all chloride concentrations (from 0.02 to 0.3 M), and its value was not dependent on the total Ru content in the material structure. The reaction mechanism with respect to chlorine evolution reaction was discussed on the basis of the determined order of reactions, which apparently increases with increasing Ru content.

Melting of the charge-ordered state in Y0.5Ca0.5MnO3 through Ru-substitution and consequent development of ferromagnetic and magnetocaloric behavior

The effect of Ru-substitution (5–15 %) on the charge ordering of Y0.5Ca0.5MnO3 has been investigated in this paper. Ru, existing in different oxidation states such as Ru4+ and Ru5+, plays an immense role in causing ferromagnetic (FM) superexchange interactions with Mn3+ ions. This, combined with the FM double-exchange interactions between Mn3+ and Mn4+ ions, destroys charge ordering. The development of ferromagnetism in Ru-substituted compounds is understood experimentally through the remarkable enhancement of dc magnetization with a simultaneous shift of TC from 57 K to 95 K with increasing Ru content from x = 0.05 to x = 0.15. The appearance of hysteresis for higher doping concentrations further confirms the FM nature. Concomitant with the favorable impact on the magnetic nature, there is also a development of magnetocaloric properties upon Ru-substitution. The maximum magnetic entropy change for x = 0.05 to 0.15 that was found to peak at TC ranges from 1.08 J/kg/K to 2.8 J/kg/K respectively for a field change of 9 T. The corresponding relative cooling power (RCP) increases from 76 J/kg to 324 J/kg indicating a significant growth of RCP with Ru substitution. These salient features of Ru-doped Y0.5Ca0.5MnO3 would make it a suitable candidate for magnetic refrigeration.

Influence of Ru on high-temperature creep rupture properties and oxidation behavior of Ni-based single-crystal superalloys

The present study investigates the microstructure, high-temperature creep rupture properties and oxidation resistance of three fourth-generation single-crystal Ni-based superalloys containing 0, 3.5 and 7 wt% of Ru. The addition of Ru changes the partitioning behavior of the alloying elements, decreases γ' size and increases the γ/γ' lattice misfit. The creep resistance keeps increasing as Ru content rises up 7 wt% under 1100 °C/140 MPa. However, it was discovered that 7 wt% Ru alloy has inferior creep resistance compared with the 3.5 wt% Ru one under 1150 °C/140 MPa, although no TCP precipitation was observed in this 7 wt% Ru-containing alloy. It was revealed that 7 wt% Ru-addition caused significant γ' dissolution and induced the generation of creep cavities, which may account for the anomaly. Furthermore, the increase in Ru content up to 7 wt% keeps degrading the oxidation resistance of the superalloys by facilitating the formation of pores and cracks within the oxide scales, which also accelerate scale spallation. This work suggests that excess Ru addition may adversely affect both the mechanical properties and the oxidation resistance of the fourth-generation Ni-based superalloys.

Preparation of Ru/C hydrogen evolution catalyst by mixed salt co-electroreduction of RuCl3*nH2O and CO2

Ruthenium carbon (Ru/C) catalyst is obtained by co-electroreduction of carbonate and ruthenium ions in mixed sodium carbonate, sodium chloride, calcium oxide molten salts (Na2CO3-NaCl-CaO) from carbon dioxide (CO2) and hydrated ruthenium chloride (RuCl3*nH2O). Irregular particles with Ru loaded on carbon, Ru particles coated by carbon and nanocarbon fibers filled with Ru are prepared. Ru/C catalysts with different Ru content of 16.0 wt%, 36.5 wt% and 76.8 wt% are obtained. With the increase of Ru content, the overpotentials (-10 mA cm−2) for HER are respectively 110.8 mV, 198.4 mV, 31.9 mV in strong acid electrolyte (0.5 M H2SO4) and 50.2 mV, 197.9 mV, 16.8 mV in strong alkaline electrolyte (1.0 M KOH). Ru/C prepared at 800 °C, 3.0 V and RuCl3*nH2O content of 1.0 wt% for electrolysis 6 h are of more advantageous for application. The stability of Ru/C catalyst still needs to be improved in 1.0 M KOH. In final, Ru/C electrocatalysts for HER can be successfully prepared by a green route of molten mixed salt from RuCl3*nH2O and CO2.

Decreasing the Carrier Concentration of ZrNiSn: An Opposite Way to the Best N-Type Half-Heusler Thermoelectrics.

N-type ZrNiSn-based alloys reach a record thermoelectric figure of merit zT ≈1.2 by increasing the carrier concentration to 4-5 × 1020 cm-3 . In this work, It is reported that a comparable zT can also be realized in trace Ru-doped ZrNiSn-based alloy at even lower temperature by decreasing the carrier concentration. Compared to the previously reported Co doping, the doping of Ru results in a more effective reduction in carrier concentration, and thus higher Seebeck coefficient, lower electronic thermal conductivity, and enhanced thermoelectric performance. The electronic specific heat coefficient of the ZrNi1- x Rux Sn sample remains constant with increasing Ru content, indicating no obvious change in the density of states effective mass. Theoretical calculations show that the doping of Ru has negligible effect on the bottom of conduction band. The lattice thermal conductivity is further reduced by alloying Ti and Hf at the Zr site, and the bipolar diffusion is suppressed by doping of 0.5 at.% Sb. As a result, Ti0.25 Zr0.5 Hf0.25 Ni0.99 Ru0.01 Sn0.995 Sb0.005 reaches not only a zT value of 1.1 at 773 K but also a record average zT value of 0.8 in 300 to 873 K, demonstrating the effectiveness of trace Ru doping on boosting the thermoelectric performance of ZrNiSn-based alloys.

The Influence of Doping Perimidine Ruthenium Complexes on Structural, Optic, and Residual Stress Properties of ZnO Thin Films

Perimidine ruthenium complexes ([Ru(L1-2)(p-cymene)Cl]Cl) were synthesized and were used to produce Ru-doped ZnO thin films by the sol–gel spin-coating method. These films were characterized using XRD, SEM, FT-IR, UV–Vis, and photoluminescence (PL) spectra. It was determined by XRD analysis that all films have a hexagonal wurtzite structure. The residual stress was generally compressive and ranged from − 2.117 to 1.4 GPa as the ruthenium content increased from 0 to 6%. The crystal quality tended to increase, and the residual stress reduced with increasing Ru content. In the visible range, all the films exhibited transmittance greater than 70%. Further, the optical bandgap was 3.20 eV for pure film and bandgap of Ru-doped films varied between 2.76 and 3.18 eV. This research shows that new high conjugated structures are promising as dopant materials for the ZnO thin film, and good crystalline and optical properties could be obtained from the Ru-doped ZnO films prepared for nano-optoelectronic devices.

Structural and magnetic properties of Ca3Mn2−xRuxO7(0<x≤0.9)

We here report on the study of the crystallographic and magnetic properties of layered perovskites ${\mathrm{Ca}}_{3}{\mathrm{Mn}}_{2\ensuremath{-}x}{\mathrm{Ru}}_{x}{\mathrm{O}}_{7}$ ($x\ensuremath{\le}0.9$). We observe a solid solution between Mn and Ru atoms in the whole series and all samples present the same orthorhombic structure independently of the Ru content. Different magnetic structures, depending on the Ru content in the sample, have been determined using neutron powder diffraction. For low Ru doping ($x\ensuremath{\le}0.1$), there is a dominant $G$-type antiferromagnetic ordering in the perovskite bilayers but, differently from undoped ${\mathrm{Ca}}_{3}{\mathrm{Mn}}_{2}{\mathrm{O}}_{7}$, the magnetic moments are located on the $ab$ plane. For higher Ru concentration ($x\ensuremath{\ge}0.3$), the predominant $G$-type ordering is preserved along the $y$ axis while an $A$-type component is developed along the $x$ axis and its intensity increases as Ru content does. This component is characterized by a ferromagnetic ordering in the $a$ direction of one of the $Mn(\mathrm{Ru}){\mathrm{O}}_{6}$ layers, coupled antiferromagnetically with the neighbor $\mathrm{Mn}(\mathrm{Ru}){\mathrm{O}}_{6}$ layer within the same bilayer. The study of the macroscopic magnetic properties shows that ferromagneticlike correlations are enhanced with increasing Ru content as deduced from the shift to higher temperature of the onset of the magnetic transition temperature. The magnetic transitions take place in two steps. At higher temperatures (140--200 K), short-range magnetic correlations are established. Tiny spontaneous magnetization is observed in the hysteresis loops with small coercive field. At ${T}_{\mathrm{N}}\ensuremath{\approx}115--125\phantom{\rule{0.16em}{0ex}}\mathrm{K}$, long-range antiferromagnetic ordering is developed. The ferromagnetic component remains with a strong increase of coercivity. We discuss in the paper the possible origins of this ferromagnetic contribution.

Low temperature dry reforming of methane using Ru-Ni-Mg/ceria-zirconia catalysts: Effect of Ru loading and reduction temperature

Dry reforming catalysts, especially those with activity at moderate temperatures, have been intensely investigated to enhance the conversion of biogas. Here, Ru is evaluated as a promoter for Ni-Mg based catalysts. Catalysts based on 1.4 wt%Ni-1.0 wt%Mg-Ce0.6Zr0.4O2 with Ru (0.02–0.32 wt%) were prepared using incipient wetness. The reducibility of the catalysts and conversions increased with increasing Ru content. Increases in conversions with increasing Ru loading was attributed to the additional active sites and synergistic effect between Ru and Ni, which weakened Ni-Mg interactions. Samples showed dry reforming activity at low temperatures (450–510 °C). Reaction rates and activation energies of higher loading Ru samples (1.4 wt%Ni-1.0 wt%Mg/Ce0.6Zr0.4 O2 with 0.16 and 0.32 wt%Ru) decreased when the reduction temperature was raised from 300 to 400 °C. A 20 h TOS study showed stable catalytic activity with minimal coke deposition. The results suggest that Ru is an alternative to Pt in promoting low temperature dry reforming of methane.

Hydrothermal gasification of phenol with Ru added carbon-metal oxide composite-supported Ni catalysts prepared by sol-gel method

Ru promotion effect on carbon-metal oxide composite-supported Ni catalysts were tested for hydrothermal gasification of phenol in aqueous phase as a model process of wastewater treatment. The catalysts were prepared by the combination of aluminum, titanium and zirconium alkoxide, and polyethylene glycol as an organic template, with the addition of active metals, nickel nitrate hexahydrate and ruthenium chloride. In the hydrothermal gasification at 350 °C, pressure 20 MPa and phenol concentration in water 20 g/L, the effect of the addition of Ru to Ni/C/oxide was observed and the conversion of phenol increased. When the effect of metal oxide was compared at 5 wt% of Ru and 16 wt% of Ni contents, the conversion of phenol increased in the order ZrO2 < Al2O3 < TiO2. The activity of Al2O3 -supported catalysts increased with increasing Ru content while that of TiO2 -supported catalysts did not change with the Ru content.

Quantitative study on Ru local atomic structure in Ni-Al-Ru ternary alloys

The synchrotron radiation X-ray absorption fine structure (XAFS) technique is used to study the local structure of the key atom Ru in a series of Ni-Al-Ru ternary alloys with different Ru contents and heat treatments. All the investigated alloys consist of two phases, γ and γ', and especially Ru exists as an atom coordinated by 12 Ni atoms in the first shell without Ru clusters or intermetallic compounds. In γ phase Ru resides on the Ni lattice site introducing an outward relaxation of the neighboring atoms, while in the γ' phase Ru replaces the Al lattice site causing an inward relaxation. The interatomic distance of Ru–Ni bond and Debye-Waller factor are mainly affected by the composition and increase with the increasing Ru content. While the effect of heat treatment is obvious when the Ru content is higher than 6 at%. The variation of Ru local atomic structure can greatly influence the microstructural evaluation and deformation mechanism by changing the lattice misfit and the vacancy formation energy to control the creep properties of Ni-Ru-Al ternary alloys.

Spectroscopic Properties and Micro-Structure for Promising Solar Cell Application of Ruthenium-Diphenyl Carbazide (RuDPC) Complex

The variation in the modes of a new ruthenium diphenyl carbazide complex (RuDPC) during changing of ruthenium (Ru) concentration within 0.01 ≤ X ≤ 0.09 in diphenyl carbazide (DPC) are investigated using IR analysis. Variation in some IR spectroscopic parameters during the increase of Ru content in pure DPC has been recorded. The variation in both the relaxation time and the rotational energy barrier for RuDPC samples at the mode 505 cm-1 supports a change that occurs at X ≈ 0.05. Micro-structure of RuDPC samples was studied by X-ray analysis and scanning electron microscopy. Moreover, SEM pictures and EDAX measurements were made revealing the strong Ru-signals indicating the presence of Ru and their distributions in the DPC matrix. Also results indicated that Ru inclusion in DPC matrix changes its morphology with a uniform distribution of Ru. Besides, X-ray diffraction patterns revealed RuDPC samples are represented by a mixture of amorphous and crystalline structure, wherever the phase-nature crystallization of RuDPC samples reinforced when the concentration of Ru is augmented. The crystal structure is changed to tetragonal structure after addition of ruthenium metal to pure orthorhombic DPC matrix. The spectroscopic properties of RuDPC complex is seemed to be dependent on its characteristics to the effect of radiation (FTIR), as a solar material in the application of this field; due to DPC is a photosensitive material, so that there are a number of optical applications which depend upon optically induced structure transition energy states for the complex.

The Effect of Ru on the Evolution of the γ' Phase in Ni-Al-Ru Alloys.

With the development and wide application of nickel-based single-crystal superalloys, the effect of Ru on the microstructure stability and high-temperature properties of superalloys is becoming increasingly important. In this study, the effect of Ru on the evolution of the γ′ phase in Ni-Al-Ru ternary alloys during aging treatment was analyzed, using a scanning electron microscope and transmission electron microscope, combined with energy-dispersive spectroscopy. The relationship between chemical partition behavior and γ/γ′ lattice misfit was investigated in detail. During the aging process, Ru addition suppressed the growth rate and rafting process of γ′ precipitates, while the effect of Ru on hindering γ′ phase growth was reduced when the Ru content was over 3 at%. Ru preferentially partitioned to the γ phase, and its partitioning ratio to the γ phase increased with a variation in Ru content from 1 at% to 3 at% and decreased for the NiAl6Ru alloy. Additionally, the lattice misfit of all alloys was positive and reduced with the increase in Ru content, which hindered the Ru atoms to diffuse into the γ phase and promoted the shape of γ′ precipitates to change from cubic to spherical.

RuxBi1‐x‐oxide as an electrode material for pseudocapacitors

AbstractThe influence of RuxBi1‐x‐oxide composition on the materials' charge storage/delivery capabilities as potential supercapacitor electrode materials was investigated in an alkaline medium. The oxides were produced as 2D coatings on a Ti substrate and were characterized by employing cyclic voltammetry, galvanostatic charge/discharge, electrochemical impedance spectroscopy, and scanning electron microscopy techniques. It was found that with an increase in Ru content in the binary oxide, the corresponding specific areal capacitance increased, reaching a maximum value of 338 ± 4 mF/cm2 at the current density of 3 mA/cm2 for the Ru0.6Bi0.4‐oxide composition, and then decreased with a further increase in Ru content. Ru0.6Bi0.4‐oxide was found to retain ~72% of its initial charge storage capacity after 5000 charging/discharging cycles at a high current density (200 mA/cm2). These results indicate that Ru0.6Bi0.4‐oxide exhibits excellent charge storage/delivery capabilities and could be a potential candidate for nanostructured electrode materials for supercapacitors.

Ultrafine PdRu Nanoparticles Immobilized in Metal–Organic Frameworks for Efficient Fluorophenol Hydrodefluorination under Mild Aqueous Conditions

Ultrafine PdRu Nanoparticles Immobilized in Metal–Organic Frameworks for Efficient Fluorophenol Hydrodefluorination under Mild Aqueous Conditions

Ru4+-assisted phase transition in VO2 nanoparticles: Electronic structures and optical properties

VO2 is a promising thermochromic material for smart windows. The major challenge for its practical application is to strike a balance between a comfortable phase transition temperature (Tc) close to room temperature and high transmittance (T) in the visible light range. Herein, we investigated the phase transition behavior of Ru-doped VO2 using first-principles calculations. The results showed that Ru-doped VO2 can be more easily realized under O-rich conditions than under V-rich conditions. Tc is sensitive to the Ru-dopant concentration and dopant symmetry, which are related to changes in the atomic and electronic structures. Furthermore, the optical band gap for RuxV1-xO2(M) first increases and then decreases with increasing Ru content. Moreover, the switching between insulating and metallic states in RuxV1-xO2(M) can be modulated by controlling the Ru-dopant concentration, and the band gap is reduced from 0.69 eV to 0 eV with increasing Ru-dopant concentration. Additionally, Ru doping can enhance the visible and infrared light transmission (T) of VO2 materials within their very narrow energy ranges. These results provide another way to promote the thermochromic properties of VO2 for application in smart windows.

Microstructure, mechanical properties, and cutting performances of WC-Co cemented carbides with Ru additions

In this study, the microstructure, mechanical properties, and cutting performance of WC-8Co cemented carbide with different Ru additions were studied in detail. The results show that Ru can inhibit the abnormal growth of WC grains and the mean grain size of WC grains decreases. Ru can result in the lattice distortion of Co phases and promote the phase transition of Co from face-centered cubic (FCC) to hexagonal closepacked (HCP) as Ru can reduce the stacking fault energy of Co phases. The proportion of HCP Co phases increased from 14.4 to 39.6% with increasing Ru content. Meanwhile, among the five groups of cemented carbides with different Ru additions, cemented carbides with 1.5 wt% Ru exhibit the highest hardness of 1382 HV and transverse rupture strength (TRS) of 3790 MPa. The enhanced hardness and TRS were due to solid solution strengthening and phase transition of Co, respectively. The fracture toughness of cemented carbide was enhanced from 16 MPa m−1/2 with 0 wt% Ru to 19 MPa m−1/2 with 0.5 wt% Ru. Additionally, during the dry cutting of Ti–6Al–4V, the diffusion of Ti and Al elements is hindered. Therefore, the wear resistance of the tools is improved. The cutting lifetime of the cemented carbide tools with 0.5 wt% Ru increased three-fold compared to those without Ru addition.

Increasing Electrocatalytic Nitrate Reduction Performance By Tuning Adsorption through PtRu Alloying

Nitrate (NO3 −) is one of the world’s most common water pollutants because of massive global fertilizer overusage, which imbalances the global nitrogen cycle. High nitrate levels in water are not only toxic to humans but also promote harmful algal blooms and dead zone formations.1 Electrocatalytic nitrate reduction (NO3RR) is a promising approach to convert nitrate into value-added (NH3) or benign (N2) products by using renewable electricity sources without an external H2 stream.2 Devices using NO3RR could ultimately reduce anthropogenic effects on the nitrogen cycle. However, NO3RR requires improved electrocatalysts that are sufficiently active, selective, stable, and inexpensive to be industrially and economically viable.Using first-principles microkinetic modeling, we predicted that a Pt3Ru alloy could be an active and selective NO3RR catalyst.3 In this talk, we confirm our computational predictions by experimentally synthesizing different compositions of Pt x Ru y /C (x = 48–100%) and characterizing their intrinsic activity and selectivity for nitrate reduction. By increasing Ru content, we show optimal nitrate and hydrogen binding energies that maximizes the electrocatalytic activity. Additionally, we demonstrate that these catalysts are selective towards ammonium (NH4 +) at 0.1 V vs. RHE.To accomplish this work, a series of Pt x Ru y /C alloys were synthesized using a modified NaBH4 reduction method with varying Ru compositions ranging from 0 to 52 at% of the total metal loading. Bulk structural characterization was performed by using X-ray diffraction, extended X-ray absorption fine structure, X-ray absorption near edge structure, and transmission electron microscopy. To ensure that intrinsic catalyst activities were normalized properly, we used hydrogen and copper underpotential deposition to measure the electrochemical active sites and compared these values to surface compositions determined by X-ray photoelectron spectroscopy. The catalysts were deposited onto a glassy carbon electrode for intrinsic steady-state current measurements at different operating potentials. Steady-state intrinsic activity measurements show that PtxRuy/C alloys are more active than Pt/C, with Pt78Ru22/C being greater than 10 times more active (−55 μA/cm2) than Pt at 0.05 V vs RHE. Product quantification of the catalysts gives faradaic efficiencies between 70–98% towards ammonium at 0.1 V vs RHE at pH = 1. Density functional theory calculations predict increasing Pt x Ru y activity as Ru content increases to 25 at%, followed by a decrease in activity at higher Ru content, which is qualitatively consistent with experimental measurements. Ultimately, this study clarifies how nitrate reduction electrocatalyst performance can be tuned by changing the adsorption strength of nitrate, hydrogen, and intermediate species through alloying.References Yao, F., Yang, Q., Zhong, Y., Shu, X., Chen, F., Sun, J. Ma, Y., Fu, Z., Wang, D., Li, X., Water Res, 157, 191-200 (2019).Singh, N. and Goldsmith, B. R. ACS Catal. 2020, 10, 5, 3365-3371 (2020).Liu, J.-X., Richards, D., Singh, N., Goldsmith, B. R., ACS Catal. 9, 8, 7052-7064 (2019).

Effect of Metal Composition and Carbon Support on the Durability of the Reversal-Tolerant Anode with IrRu Alloy Catalyst

In polymer electrolyte membrane fuel cells (PEMFCs) for fuel cell electric vehicles, cell reversal (CR) at the anode side can occasionally occur—usually when hydrogen supply is interrupted—which results in degradation of the anode. To mitigate this problem, reversal-tolerant anodes (RTAs) using oxygen evolution reaction catalysts have been generally applied. Adding such materials promotes water oxidation and, thus, provides the protons and electrons during CR situation, while minimizing the carbon-oxidation reaction. In this study, we performed a detailed investigation of the sole use of IrxRuy/C catalysts for RTAs in the membrane electrode assembly (MEA)—including the effects of the IrRu alloy composition and the degree of graphitization of the carbon support on the durability under fuel starvation. Supported IrRu alloy catalysts with different Ir/Ru ratios were prepared via a facile impregnation method on carbon supports with differing degrees of graphitization by heat-treatment at a range of high temperatures. X-ray diffraction patterns indicated that the crystal structure of the alloy nanoparticles depended on the alloy composition, showing the development of a hexagonal closely packed structure with increasing Ru content. Raman spectroscopy indicated an increase in the degree of graphitization of carbon with progressively higher processing temperatures. IrxRuy alloys were found to be a suitable replacement for Pt anode from single-cell MEA performance testing. Furthermore, we examined the synergic enhancement of the CR durability of IrRu alloys with different compositions comparing to the Ir and Ru metals by measuring the initial and total voltage change of MEAs under hydrogen starvation. For the same alloy composition, higher CR durability was observed for MEAs with catalysts prepared using a higher degree of graphitization of the carbon support. Based on the results, we concluded that to develop efficient catalysts for RTAs of automotive PEMFCs, it is important to consider both the durability of the carbon support under high voltages and the catalyst composition.

Effects of Ru substitution on the structural, magnetic and magnetocaloric properties of Pr0.68Ca0.22Sr0.1Mn1−xRuxO3 (x = 0, 0.05, 0.1 and 0.2) compounds

The structural, magnetic and magnetocaloric properties of polycrystalline Pr0.68Ca0.22Sr0.1Mn1−xRuxO3 (x = 0, 0.05, 0.1 and 0.2) compounds were studied. All the samples crystallized in an orthorhombic symmetry. A significant increase in the lattice parameters in the doped samples was attributed to the existence of Ru with a the mixed-valence state (Ru3+/Ru4+). The increase in the Curie temperature (Tc) with increasing Ru content was interpreted as Ru doping promoting the ferromagnetic interactions between Ru4+–Mn3+ and Ru4+–Mn4+pairs. The decrease in saturation magnetisation was attributed to an AFM interaction between the Ru3+–Mn3+ and Ru3+–Mn4+ pairs and smaller magnetic moments of Ru than those of Mn. The decrease in |ΔSM| (from 4.66 J kg−1 K−1 for x = 0.05 to 2.32 J kg−1 K−1 for x = 0.2 at 5 T) was attributed to the nature of phase transition (from a first-order to second-order transition) and a decrease in the saturation magnetisation.