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Synthesis and optical properties of novel double perovskite Ca_(2)MgTeO_(6):Dy^(3+),Na^(+) phosphors for white LEDs

Journal of Rare Earths 2021年第6期39卷 634-642,I0001页

作者： Junzhi Che Bin Deng Qinyang Song Jianxu Wang Tao Wang Shoucheng Zhao Ruijin Yu College of Chemistry&Pharmacy Northwest A&F UniversityYangling 712100China College of Chemistry&Biology and Environmental Engineering Xiangnan UniversityChenzhou 423043China Hunan Provincial Key Laboratory of Xiangnan Rare-Precious Metals Compounds Research and Application Chenzhou 423043China Key Laboratory of Inorganic Nonmetallic Crystalline and Energy Conversion Materials College of Materials and Chemical EngineeringChina Three Gorges UniversityYichang 443002China

Novel yellow-emitting phosphors of Dy^(3+)-doped double perovskite Ca_(2)MgTeO_(6) were synthesized by using a conventional high-temperature solid-state *** phase purity,particle morphology,size distribution,elemental composition,luminescence properties,and luminescence decay curves of the resulting products were then analyzed in *** Ca_(2)MgTeO_(6):Dy^(3+),Na^(+) phosphors show three emission peaks after near-ultraviolet excitation at 350 nm,which correspond to ^(4)F_(9/2)→^(6)H_(11/2),^(4)F_(9/2)→^(6)H_(13/2),and ^(4)F_(9/2)→^(6)H_(13/2) transitions,*** them,the strongest peak is observed at 573 *** best doping content of Dy^(3+)in Ca_(2)MgTeO_(6):xDy^(3+),xNa^(+) phosphors is x=5 mol%.The calculated critical distance of energy transfer between Dy^(3+) ions is 1.6 *** quenching is confirmed to be due to dipole-dipole interactions among Dy^(3+) *** phosphors show excellent thermal stability with high activation energy(0.27 eV).The Commission Internationale de l’Eclairage(CIE) chromaticity coordinates of the Ca_(2)MgTeO_(6) Dy^(3+),Na^(+) phosphors are located in the yellow *** light-emitting diodes(w-LEDs) were fabricated with a high color rendering index(R_(a)) of 88 and a good correlated color temperature(CCT) of 5440 *** observed properties indicate that Ca_(2)MgTeO_(6):Dy^(3+),Na^(+) phosphors have potential applications in display and photonic devices.

关键词： Luminescence double perovskite Ca_(2)MgTeO_(6) Phosphor Rare earths

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Surface structure and catalytic performance of Sr-doped La_2NiAlO_6 double perovskite catalysts for methane combustion

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Journal of Rare Earths 2015年第12期33卷 1284-1292页

作者：胡瑞生白雅琴杜航宇张慧敏杜燕飞张俊阁周啟华 School of Chemistry and Chemical Engineering Key Laboratory of Rare Earth MaterialsInner Mongolia University Department of Chemical Engineering Hohhot Vocational College

A species of novel St-doped rare earth double perovskite catalysts （La2 xSrxNiA106, x=0, 0.1） were prepared by the sol-gel method using citric acid as a complexing agent and calcined at 1100 ℃ for 3 h, then investigated for methane catalytic combustion. The as-prepared catalysts were characterized by X-ray diffraction patterns （XRD）, H2-temperature-programmed reduction （H2-TPR）, specific surface area （BET）, magnetic property measurement technology （M-H）, scanning electron microscopy （SEM）, and X-ray photoelectron spectroscopy （XPS）. Experimental results showed that Lal.9Sr0.1NiA106 catalyst exhibited significantly improved catalytic activity （T10=378.7 ℃, T90=602.9 ℃） compared with that of La2NiAIO6, whose T10 decreased by 74.4 ℃ and T90 decreased by 66.8 ℃, respectively. The excellent catalytic activity of ***106 caused by Sr-doping could be explained by the larger number of adsorption oxygen on the catalyst surface, which could be proven by XPS analysis.

关键词： rare earths double perovskite methane catalytic combustion sol-gel method

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Structural phase transition and dielectric switching in an organic-inorganic hybrid rare-earth double perovskite-type compound:(DMP)_(2)LaRb(NO_(3))_(6)(DMP=N,N-dimethylpyrrolidinium cation)

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Journal of Rare Earths 2022年第6期40卷 937-941,I0004页

作者： Jiajun Ma Qi Xu Le Ye Qinwen Wang Zhixin Gong Chao Shi Hengyun Ye Yi Zhang Chaotic Matter Science Research Center Jiangxi University of Science and TechnologyGanzhou 341000China

In recent years,it has been found that the flexibility of structure and diversity of the components endow quite an amount of the organic-inorganic hybrid perovskites with novel properties,i.e.,structural phase *** the natural advantage of the perovskite-type structure in generation of stimuliresponsive or smart materials,we synthesized an organic-inorganic hybrid rare-earth double perovskitetype compound,(DMP)_(2) LaRb(NO_(3))_(6)(DMP=N,N-dimethylpyrrolidinium cation,1).It shows reversible phase transition at 219/209 K(heating/cooling).Variable-temperature single-crystal structure analysis and dielectric constant measurements reveal that the thermal vibrations of the polar cation guests and the distortion of the anionic cage-like framework are the origin of the phase ***,the movement of polar cation in crystal lattices arouses dielectric transition between the low-and highdielectric states,resulting in a switchable property of dielectric *** results reveal that the rare-earth double perovskite provides a promising platform for achieving switchable physical/chemical properties.

关键词： Switchable dielectric constant Phase transition Rare earths double perovskite

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Synthesis and enhanced luminescence properties of double perovskite NaLa0.95-xYxEu0.05MgWO6 phosphors

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Rare Metals 2020年第8期39卷 895-901页

作者： Jing Zhang Jia-Lin Shen Nai-Cen Xu Nanjing Center China Geological SurveyNanjing 210016China Supervision and Testing Center of East China Mineral Resources of the Ministry of Land and ResourcesNanjing 210016China

double perovskite Na(La,Y)MgWO6:Eu3+phosphors were obtained by the sol-gel method.X-ray diffractometer(XRD)patterns,scanning electron microscopy(SEM)images and photoluminescence properties were carried out to study the effect of polyethylene glycol(PEG).Enhanced optical properties were obtained by adding 3 wt%PEG under the excitation of 395 nm.Y3+with smaller radius was selected to substitute La3+in this host to decrease the symmetry and further enhance the luminescence *** Y3+concentration increasing,Na2WO4 and Y30W8O69 phases came *** emission spectra showed different shapes,and the emission intensity was enhanced by doping Y3+.Under the excitation of 395 and 465 nm,the emission intensity reached the *** Commission Internationale de L’Eclairage(CIE)coordinates of the phosphors were on the edge of the CIE diagram,illustrating that this double perovskite phosphor showed good color *** luminescence properties showed that the synthesized phosphors had great potential in solid-state lighting.

关键词： double perovskite Structure evolution Phosphors White light emitting diodes

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Luminescent ionic lattice occupation and wide tunable emission spectra of La_(2)MgZrO_(6):Bi^(3+),Eu^(3+)double perovskite phosphors for white light LED

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Journal of Rare Earths 2023年第4期41卷 489-497页

作者： Chen Yang Chenli Fan Fayaz Hussain Weiqing Sheng Kaixin Song Jun Wu Qingming Huang Weitao Su Junming Xu Shikuan Sun Dawei Wang College of Electronics Information Hangzhou Dianzi UniversityHangzhou 310018China Department of Materials Engineering NED University of Engineering and TechnologyMain University RoadKarachi75270Pakistan Testing Center of Fuzhou University Fuzhou UniversityFuzhou 350116China College of Sciences Hangzhou Dianzi UniversityHangzhou 310018China School of Material Science and Energy Engineering Foshan UniversityFoshan 528000China Shenzhen Institute of Advanced Electronic Materials Shenzhen Institute of Advanced TechnologyChinese Academy of SciencesSciencesShenzhen 55China

La_(2)Mg_(1-x/2)Zr_(1-x/2)O_(6):xBi^(3+)(x=0.01-0.035,abbreviated as LMZ:Bi^(3+))and La_(2-y)Mg_(0.99)Zr_(0.99)O_(6):0.02Bi^(3+),yEu^(3+)(y=0.1-0.11,abbreviated as LMZ:Bi^(3+),Eu^(3+))double-perovskite phosphors were prepared through high-temperature solid-phase *** emission spectrum of LMZ:xBi^(3+)(x=0.01-0.035)phosphors excited at 353 nm is asymmetric in the range between 375 and 650 nm,showing strong green *** are two luminescent centers of[Mg1/Zr2-O_(6)]and[Mg2/Zr1-O_(6)]for Bi^(3+)occupation,which were analyzed through different excitation wavelengths,Gaussian fitting peaks,fluorescence decay curves and Rietveld refinement of powder X-ray diffraction *** deep study of the luminescent lattices in the LMZ matrix,the green to blue tunning-emission is observed by different excitation *** addition,red emission is obtained by co-doping Bi^(3+)/Eu^(3+),and adjustable emission was investigated by changing the content of Eu^(3+)in the co-doped phosphor formulation,so it is converted from green emission to red *** above results demonstrate how to tune emission color by co-doping rare earth ions in the double perovskite phosphor,which is attractive for future applications.

关键词： double perovskite Phosphor Tunable emission Energy transfer Rare earths

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Synthesis,crystal structure and photoluminescence properties of novel double perovskite La2CaSnO6:Eu3+red-emitting phosphors

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Journal of Rare Earths 2022年第11期40卷 1682-1690,I0001页

作者： Yangyi Xu Guifang Li Xufeng Guan Yunge Wei Maolin Zhang School of Advanced Materials and Nano Technology Xidian UniversityXi'an710071China

A series of new double perovskite LaEuCaSnO(0≤x≤0.8)red phosphors were synthesized by traditional solid-state *** phase,micro structure,photoluminescence(PL)properties,quantum efficiency,and thermal stability of the phosphors were *** has a monoclinic double perovskite structure with space group P2/*** near-ultraviolet(UV)light at395 nm,LaEuCaSnOphosphors exhibit the most typical red emission peak at 614 nm,which corresponds to~5 D→~7 Felectric dipole transition of *** optimum Eudoping content is attained at x=0.5,and the LaEuCaSnOphosphor shows a moderate quantum efficiency(32.3%)and high color purity(92.2%).Besides,the temperature-dependent spectrum of the phosphor was *** emission intensity of Euat 423 K decreases to 70.94%of the initial intensity at 303 K,and the activation energyΔE is estimated to be 0.232 eV,suggesting that the phosphors possess good thermal *** fabricated w-LED based on the phosphors has higher Ra(89),lower CCT(4539 K),and better chromaticity coo rdinates(0.371,0.428).These results prove that the Eu-doped LaCaSnOred phosphor has great potential applications in w-LEDs.

关键词： Phosphors double perovskite Luminescence properties La2CaSnO6 Rare earths

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First-principles study of the structural, electronic, and magnetic properties of double perovskite Sr2FeReO6 containing various imperfections

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Chinese Physics B 2016年第5期25卷 410-417页

作者：张研段理 Vincent Ji 徐可为 School of Materials Science and Engineering Chang'an University Xi 'an 710061 China ICMMO/SP2M UMR CNRS 8182 Universite Paris- Sud 91405 Orsay Cedex France State Key Laboratory for Mechanical Behavior of Materials Xi' an Jiaotong University Xi' an 710049 China

The structural, electronic, and magnetic properties of double perovskite Sr_2FeReO_6 containing eight different imperfections of FeReor ReFeantisites, Fe1–Re1 or Fe1–Re4 interchanges, V_（Fe）, V_（Re）, VOor V_（Sr） vacancies have been studied by using the first-principles projector augmented wave（PAW） within generalized gradient approximation as well as taking into account the on-site Coulomb repulsive interaction（GGA＋U）. No obvious structural changes are observed for the imperfect Sr_2FeReO_6 containing FeReor ReFeantisites, Fe1–Re1 or Fe1–Re4 interchanges, or VSrvacancy defects. However, the six（eight） nearest oxygen neighbors of the vacancy move away from（close to） VFeor V_（Re）（VO） vacancies. The half-metallic（HM） character is maintained for the imperfect Sr_2FeReO_6 containing FeReor ReFeantisites, Fe1–Re4 interchange, V_（Fe）,VO or V_（Sr） vacancies, while it vanishes when the Fe1–Re1 interchange or VRevacancy is presented. So the Fe1–Re1 interchange and the VRevacancy defects should be avoided to preserve the HM character of Sr_2FeReO_6 and thus usage in spintronic devices. In the FeReor ReFeantisites, Fe1–Re1 or Fe1–Re4 interchanges cases, the spin moments of the Fe（Re）cations situated on Re（Fe） antisites are in an antiferromagnetic coupling with those of the Fe（Re） cations on the regular sites. In the V_（Fe）, V_（Re）, VO, or V_（Sr） vacancies cases, a ferromagnetic coupling is obtained within each cation sublattice,while the two cation sublattices are coupled antiferromagnetically. The total magnetic moments μtot（μB/f.u.） of the imperfect Sr_2FeReO_6 containing eight different defects decrease in the sequence of VSrvacancy（3.50）, VRevacancy（3.43）,FeReantisite（2.74）, VOvacancy（2.64）, VFevacancy（2.51）, ReFeantisite（2.29）, Fe1–Re4 interchange（1.96）, Fe1–Re1interchange（1.87）, and the mechanisms of the saturation magnetization reduction have been analyzed.

关键词： double perovskite imperfections electronic properties magnetic properties

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Lead-free hybrid two-dimensional double perovskite with switchable dielectric phase transition

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Chinese Chemical Letters 2024年第6期35卷 176-179页

作者： Tian Yang Yi Liu Lina Hua Yaoyao Chen Wuqian Guo Haojie Xu Xi Zeng Changhao Gao Wenjing Li Junhua Luo Zhihua Sun College of Chemistry Fuzhou UniversityFuzhou 350108China State Key Laboratory of Structural Chemistry Fujian Institute of Research on the Structure of MatterChinese Academy of SciencesFuzhou 350002China

Molecular dielectric switches constitute a type of intelligent materials that are highly coveted for their distinctive advantages of switchable dielectric responses,lightweight,and mechanical ***(2D)hybrid perovskites have demonstrated excellent promise for assembling dielectric switches,in which the dynamic motions of organic moieties afford driving force to trigger switchable dielectric phase ***,we successfully assembled a new lead-free hybrid double perovskite,(CHA)4Cu Bi Br8(1,CHA=cyclohexylammonium),adopting a typical 2D structural motif,which shows dielectric anisotropy and bistable behaviors during the reversible phase transition near T_(c)=378 K(the Curie temperature).That is,its dielectric constants could be switched and tuned between high-dielectric and low-dielectric *** analyses reveal that the ordered-disordered transformation of the organic CHA+moiety and distortion of inorganic framework account for its phase *** result will stimulate further exploration of molecular dielectric switches in this 2D environmentally friendly family.

关键词： Dielectric switch Lead-free double perovskite Phase transition Symmetry breaking

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Doping strategy on improving the overall cathodic performance of double perovskite LnBaCo_(2)O_(5+σ)(Ln=Pr,Gd)as potential SOFC cathode materials

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Journal of Materiomics 2023年第5期9卷 825-837页

作者： Fangze Chen Dacheng Zhou Xueqing Xiong Juntao Pan Donglin Cai Ze Wei Xiyong Chen Yihui Liu Nengneng Luo Jialin Yan Toyohisa Fujita State Key Laboratory of Featured Metal Materials and Life-cycle Safety for Composite Structures Guangxi UniversityNanning530004GuangxiChina School of Resources Environment and MaterialsGuangxi UniversityNanning530004GuangxiChina Hubei Key Laboratory of Advanced Technology for Automotive Components&Hubei Collaborative Innovation Center for Automotive Components Technology Wuhan University of TechnologyWuhan430070HubeiChina

A series of single-phase double perovskite Pr1-xGdxBaCo_(2)-yFeyO_(5+σ)(x=0,0.5 and 1,0≤y≤1)materials were engineered through A/B site co-doping strategy to improve the mechanical,electrical and electrochemical properties as potential cathode materials for the application of intermediate solid oxide fuel cells(IT-SOFCs).The corresponding thermochemical stability,thermal expansion behavior,electrical conductivity and cathodic polarization resistance of the materials were systematically *** was found that the A-site dual lanthanide doped Pr_(0.5)Gd_(0.5)BaCo_(2)O_(5+σ)(PGBCO)exhibits improved electrical conductivity,reduced thermal expansion,and comparatively low electrochemical polarization resistance versus single lanthanide double perovskite,PrBaCo_(2)O_(5+σ)(PBCO)and GdBaCo_(2)O_(5+σ)(GBCO)*** investigation on the effect of B-site Fe-doping on Pr_(0.5)Gd_(0.5)BaCo_(2)-yFeyO_(5)+σ(PGBCF-y,0≤y≤1)reveals that all the PGBCF-y compositions exhibit excellent chemical stability with Gd-doped ceria(GDC)at operating temperatures not higher than 1100℃.Besides,doping of Fe in B-site can effectively reduce the thermal expansion coefficients(TECs)of the Pr_(0.5)Gd_(0.5)BaCo_(2)O_(5)+σceramics at 30e1000℃.And the electrochemical impedance spectra(EIS)results show that the PGBCF-y|GDC|PGBCF-y symmetric cells have acceptable low area specific polarization *** examination of the cathodic polarization and characteristic capacitance from the AC impedance spectra by employing the relaxation time distribution(DRT)method demonstrated that charge transfer is the dominating subprocess for the oxygen transport through the materials.

关键词： double perovskite Electrical conductivity Thermal expansion Electrochemical polarization Thermochemical stability

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Bismuth-based halide double perovskite Cs_(2)KBiCl_(6): Disorder and luminescence

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Chinese Chemical Letters 2024年第5期35卷 504-508页

作者： Pan Liu Yanming Sun Alberto J.Fernández-Carrión Bowen Zhang Hui Fu Lunhua He Xing Ming Congling Yin Xiaojun Kuang MOE Key Laboratory of New Processing Technology for Nonferrous Metal and Materials Guangxi Key Laboratory of Optic and Electronic Materials and DevicesCollege of Materials Science and EngineeringGuilin University of TechnologyGuilin 541004China Analytical Instrumentation Center College of Chemistry and Molecular EngineeringPeking UniversityBeijing 100871China Spallation Neutron Source Science Center Dongguan 523803China Chinese Academic of Science Institute of PhysicsBeijing National Laboratory for Condensed Matter PhysicsBeijing 100190China Songshan Lake Materials Laboratory Dongguan 523808China College of Science Guilin University of TechnologyGuilin 541004China College of Chemistry and Bioengineering Guilin University of TechnologyGuilin 541004China

A new bismuth-based halide double perovskite Cs_(2)KBiCl_(6) was isolated successfully through solid-state reactions and investigated using X-ray and neutron *** than an ordered structure,the crystal structure consists of shifted Cs,K,Bi,and Cl sites from the ideal positions with fractional occupancy in compensation,leading to variable local coordination of Cs^(+)ions,as revealed by^(133)Cs solid-state nuclear magnetic resonance ***_(2)KBiCl_(6) displays volume hysteresis at 5-298 K range upon heating and *** Cs_(2)KBiCl_(6) has a direct bandgap of 3.35(2)eV and red-shift luminescence of around 600 nm upon Mn doping compared with the Na *** stabilization of disordered structure in Cs_(2)KBiCl_(6) is related to two factors including the large-sized K^(+)cation which prefers to coordinate with more than six Cl^(-),and the Bi^(3+)with 6s^(2) lone pair which has a preference for a local asymmetric *** findings could have general application and help to understand the structure and property of halide perovskites.

关键词： Halide perovskite double perovskite Luminescence Disordered structure Direct bandgap

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