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Dielectric properties of bismuth-containing pyrochlores:A comparative analysis

Journal of Advanced Dielectrics 2022年第2期12卷 29-35页

作者： M.V.Talanov E.V.Glazunova V.I.Kozlov S.P.Kubrin A.A.Bush V.M.Talanov K.E.Kamentsev Research Institute of Physics Southern Federal University av.Stachki 193 Rostov-on-Don344090Russia Research Institute of Solid State Electronics Materials MIREA-Russian Technological University(RTU MIREA)5th Street of Sokolinaya Gora 22 Moscow 119454Russia Technological Department Platov South-Russian State Polytechnic University(NPI)Prosvescheniya Str.132 Novocherkassk 346428Russia

The comparative analysis of the dielectric properties of bismuth-containing pyrochlores with different manifestation of atomic order/disorder was carried *** examined the dielectric properties(including behavior in electric fields)of two pyrochlore compounds:BZN(presumably a composition close to Bi_(1.5)Zn_(0.5)Nb_(1.5)O_(6.5))ceramics with chemical disorder in both A and B cation sublattices and Bi_(2)Ti_(2)O_(7)single crystal with fully chemical ordered *** fundamental differences between the dielectric properties of the BZN ceramics and Bi_(2)Ti_(2)O_(7)single crystal were *** particular,in the dielectric relaxation behavior(which cannot be described via Arrhenius law in the Bi_(2)Ti_(2)O_(7))or in the influence of the electric fields on the dielectric permittivity(split-ting of the field-cooled and zero-field-cooled behaviors was observed for Bi_(2)Ti_(2)O_(7)below estimated freezing temperature).The results of this study highlights the special role of Bi_(2)Ti_(2)O_(7)as a candidate material for studying aspects of geometric frustration related with pyrochlore structure in non-magnetic medium and specifies the future directions of research.

关键词： pyrochlores relaxor behavior bismuth titanate dielectric permittivity geometric frustration

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Mechanical properties,thermal conductivity and defect formation energies of samarium immobilization in Gd_(2)Zr_(2)O_(7):First-principles study and irradiation experiment

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Journal of Rare Earths 2023年第3期41卷 422-433,I0004页

作者： Yuhao Wang Jiahu Ouyang Tao Wei Gui Cao Zhanguo Liu Zhaoying Ding Yujin Wang Yaming Wang Key Laboratory of Advanced Structural-Functional Integration Materials&Green Manufacturing Technology School of Materials Science and EngineeringHarbin Institute of TechnologyHarbin 150001China Nuclear Fuel Cycle Research Theme Australian Nuclear Science and Technology OrganisationLocked Bag 2001Kirrawee DCNSW2232Australia

A density functional theory(DFT)study was employed to investigate the mechanical property,thermal conductivity,Debye temperature,electronic structure and defect chemistry of(Gd_(1-x)Sm_(x))_(2)Zr_(2)O_(7).All the(Gd_(1-x)Sm_(x))_(2)Zr_(2)O_(7) compounds exhibit an excellent structural and mechanical stability(Gd_(0.25)Sm_(0.75))_(2)Zr_(2)O_(7) has the lowest Young’s modulus of 213.7 GPa,the largest Possion’s ratio of 0.292,the lowest Debye temperature of 491.8 K and the lowest thermal *** calculated thermal conductivities of(Gd_(1-x)Sm_(x))_(2)Zr_(2)O_(7) are 1.17-1.21 W/(m·K)by the Clark’s model and 1.32-1.36 W/(m·K)by the Cahall’s model,*** formation energies of O vacancies at 48f site are negative,which increase with the Sm content,however,the formation energies of O vacancies at 8b site are almost *** addition,Sm partly occupying the Gd-site reduces distinctly the formation energies of defects such as A-site vacancies,cation antisite defects,anion Frenkel pairs of oxygen at 8b site and cation interstitials,which suggests that Sm-doped Gd_(2)Zr_(2)O_(7),especially equimolar GdSmZr_(2)O_(7),has a better irradiation *** the 16 MeVTa-ion irradiation at a fluence of 1×10^(14) or 2×10^(14) ions/cm^(2),the crystal structure of GdSmZr_(2)O_(7) transforms from pyrochlore to a defect fluorite without obvious amorphous phase.

关键词： pyrochlores First-principles calculations Mechanical properties Defect formation energies Ion irradiation Rare earths

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Role of A-sites in pyrochlore lanthanide ruthenate for electrocatalysis of oxygen evolution reaction

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Journal of Materiomics 2024年第6期10卷 1234-1242页

作者： Hengyu Guo Zhengping Zhang Feng Wang State Key Laboratory of Chemical Resource Engineering Beijing Key Laboratory of Electrochemical Process and Technology for MaterialsBeijing University of Chemical TechnologyBeijing100029China Beijing Advanced Innovation Center for Soft Matter Science and Engineering Beijing University of Chemical TechnologyBeijing100029China

Developing highly stable and efficient catalysts for oxygen evolution reaction(OER)is extremely important to sustainable energy conversion and storage,but improved efficiency is largely hindered by sluggish reaction *** and bimetal ruthenates have emerged as one of the promising substitutes to replace single-metal ruthenium or iridium oxides,but the fundamental understanding the role of A-site cations is still ***,a family of lanthanides(Ln=all the lanthanides except Pm)are applied to synthesize pyrochlore lanthanide ruthenates(Ln_(2)Ru_(2)O_(7)),and only Ln_(2)Ru_(2)O_(7)(Ln=Sm,Eu,Gd,Tb,Dy,Ho,Er,Tm,Yb,or Lu)with pure phase can be obtained by the ambient-pressure *** with the perovskite ruthenates(SrRuO_(3))and rutile RuO_(2),the[RuO_(6)]units in these Ln_(2)Ru_(2)O_(7) present the largely distorted configurations and different energy level splitting to prevent the excessive Ru oxidation and dissolution,which leads the primary improvement in the electrocatalytic OER *** the similar crystalline field split states,the charge transfer between[RuO_(6)]units and Ln^(3+)cations also affect catalytic activities,even in the Ln_(2)Ru_(2)O_(7) surface reconstruction during the OER ***,Tb_(2)Ru_(2)O_(7) showed the highest OER performance among all the prepared Ln_(2)Ru_(2)O_(7) with similar morphologies and *** systematic work gives fundamental cognition to rational design of high-performance OER electrocatalysts in proper water electrolysis technologies.

关键词： pyrochlores Lanthanides Ruthenates Electrocatalysts Oxygen evolution reaction

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First-principles study of disordering tendencies in Gd_2B_2O_7(B=Ti,Sn,Zr) compounds

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Chinese Physics B 2010年第12期19卷 412-418页

作者：陈中钧田东斌 Department of Applied Physics University of Electronic Science and Technology of China School of Microelectronic and Solid-state Electronics University of Electronic Science and Technology of China

This paper performs the density functional theory calculations to obtain some factors influencing the response of pyrochlores Gd2B207 （B = Ti, Sn, Zr） to ion irradiation-induced amorphization. The 48f oxygen position parameter x, cohesive energy, bond type and defect-formation energy are discussed. The results show that parameter x can be used to indicate the disordering tendencies within a given pyrochlore family. Bond type, cohesive energy and defect-formation energies can be used to explain some experimental observations, but they are not determined exclusively by radiation ＂resistance＂ for a different pyrochlore family.

关键词： pyrochlores density functional theory disordering tendency electronic properties

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Specific structural features of LnZrOx(Ln:La, Sm) mixed oxides prepared by different methods

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Progress in Natural Science:Materials International 2018年第4期28卷 437-446页

作者： Tatyana Kuznetsova Tamara Kriger Yurii Chesalov ANDrey Boronin Arcadii Ishchenko Pavlos K.PANDis Vladimir Krivensov Galina Litvak Tatyana Larina Vladislav Sadykov Vassilis N.Stathopoulos Boreskov Institute of Catalysis Novosibirsk State University Laboratory of Chemistry and Materials Technology Department of Electrical Engineering School of Technological Applications Technological Education Institute of Sterea Ellada

LnZrOx(Ln: La, Sm) mixed oxides of Ln: Zr = 1 were prepared by different methods(complex polymerized method, sorption of cations on starch from aqueous salt solution and conventional co-precipitation with additional redispersion of precipitate by ultra sound) and calcined at 700–1300 °C. Their specific structural features and changes were studied and discussed. Various characterization methods were used such as X-ray diffraction,Electron microscopy, Fourier-transform infrared and Raman spectroscopy, UV–Vis spectroscopy, X-Ray absorption fine structure and X-ray photoelectron *** formation of pyrochlore structure occurred at 1100–1300 °C from fluorite-like pseudocubic phase ZrO2regardless the method of preparation. This phase had a block-like structure consisting of ZrO2nanocrystals stabilized by Ln cations and residual anions such as hydroxyls and carbonates. The desorption of such anions with heating already started at 900 °C and lead to local changes of Zr cations coordination to octahedral and to the formation of pyrochlore nanodomains inclusions within fluorite-like phase. The increased cation mobility and further elimination of anions caused by further heating was accompanied by the formation of bulk pyrochlore phase at 1100–1300 °C. Even after calcination at 1300 °C the local microheterogeneity as well as defects were identified at domains boundaries or sintered microstructure. These specific features of the formed pyrochlores depend on the method of preparation.

关键词： Fluorites pyrochlores Synthesis Powders Structure

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