Preparation and electrical conductivity of(Zr,Hf,Pr,Y,La)O high entropy fluorite oxides

A series of compositionally complex fluorite oxides(CCFOs)were prepared by ball milling the mixture of ZrO_(2),HfO_(2),Y_(2)O_(3),La_(2)O_(3),and Pr_(6)O_(11)followed by conventional solid-state sintering.Both XRD and TG-DSC results demonstrated that single-phase(Zr_(0.2)Hf_(0.2)Pr_(0.2)Y_(0.2)La_(0.2))O_(2-)δwas formed at 1400°C.Elements in bulk ceramic were uniformly distributed without evident accumulation according to SEM-EDS pictures.TEM results revealed that polycrystalline ceramic powder was assignable to cubic Fm-3m fluorite structure.The electrical conductivity(σ)was measured via EIS technology and activation energy(E_(a))of CCFOs was calculated in Arrhenius plots.In the temperature range of 300-750°C,CCFOs preserved the same conduction mechanism and(Zr_(0.1667)Hf_(0.1667)Pr_(0.1667)Y_(0.25)La_(0.25))O_(2-)δpossessed higherσand lower E_(a) than other high entropy fluorite oxides which is related to the incorporation of Pr element or the connection of cation-V_(o) complex.

Inactive Al^(3+)-doped La(CoCrFeMnNiAl_(x))_(1/(5+x))O_(3)high-entropy perovskite oxides as high performance supercapacitor electrodes

A series of high-entropy perovskite oxides(HEPOs)La(CoCrFeMnNiAl_(x))_(1/(5+x))O_(3-δ)(x=0.4,0.5,0.6,and 0.7)have been synthesized by coprecipitation method combined with calcination process and explored as electrodes for supercapacitors.The crystal structure,microstructure,and elemental composition of HEPOs were investigated by X-ray diffraction(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM),and energy-dispersive X-ray spectroscopy(EDS)in detail.The electrochemical properties of HEPOs as supercapacitor electrodes were elucidated.The specific capacitances of HEPOs(x=0.4,0.5,0.6,and 0.7)are 281.84,353.65,325.60,and 259.30 F/g at the current density of 1 A/g,respectively.After 2000 cycles,the specific capacitances of HEPOs(x=0.4,0.5,0.6,and 0.7)remain 85.01%,88.61%,86.37%,and 91.25%,respectively.Such outstanding electrochemical properties can be attributed to the entropy-stabilized structure caused by mixed six cations in B-site and the Al^(3+)-doping suppressing active ion aggregation during charge-discharge process.This research highlights the potential of HEPOs as electrodes for supercapacitors.

Ti4+-incorporated fluorite-structured high-entropy oxide (Ce,Hf,Y,Pr,Gd)O_(2−δ): Optimizing preparation and CMAS corrosion behavior

Environmental barrier coatings(EBCs)with excellent chemical resistance and good high-temperature stability are of great significance for their applications in next-generation turbine engines.In this work,a new type of high-entropy fluorite-structured oxide(Ce_(0.2)Hf_(0.2)Y_(0.2)Pr_(0.2)Gd_(0.2))O_(2−δ)(HEFO-1)with different Ti^(4+)contents were successfully synthesized.Minor addition of Ti4+could be dissolved into a high-entropy lattice to maintain the structure stable,effectively reducing the phase formation temperature and promoting the shrinkage of bulk samples.Heat treatment experiments showed that all the samples remained a single phase after annealing at 1200–1600℃for 6 h.In addition,high-entropy(Ce_(0.2)Hf_(0.2)Y_(0.2)Pr_(0.2)Gd_(0.2)Ti_(0.2x)O_(2−δ)demonstrated great resistance to calcium–magnesium–alumina–silicate(CMAS)thermochemical corrosion.When the content of Ti was increased to x=0.5,the average thickness of the reaction layer was about 10.5µm after being corroded at 1300℃for 10 h.This study reveals that high-entropy(Ce_(0.2)Hf_(0.2)Y_(0.2)Pr_(0.2)Gd_(0.2)Ti_(0.2x)O_(2−δ)is expected to be a candidate for the next-generation EBC materials with graceful resistance to CMAS corrosion.