Ceramic samples of(1-x)BiFeO_(3)-xPbFe_(0.5)Sb_(0.5)O_(3)(BFO-xPFS),(1-x)BiFeO_(3)-xSrFe_(0.5) Sb_(0.5)O_(3)(BFO-xSFS)where(x=0.05,0.1,..,0.9),(1-x)BiFeO_(3)-xBaFe_(0.5)Nb_(0.5)O_(3)(BFO-xBFN)and(1-x)BiFeO_(3)-xSrFe_(...Ceramic samples of(1-x)BiFeO_(3)-xPbFe_(0.5)Sb_(0.5)O_(3)(BFO-xPFS),(1-x)BiFeO_(3)-xSrFe_(0.5) Sb_(0.5)O_(3)(BFO-xSFS)where(x=0.05,0.1,..,0.9),(1-x)BiFeO_(3)-xBaFe_(0.5)Nb_(0.5)O_(3)(BFO-xBFN)and(1-x)BiFeO_(3)-xSrFe_(0.5)Nb_(0.5)O_(3)(BFO-xSFN)where(x=0,0.01,0.02,..,0.1,0.2,...,1)solid solutions with a perovskite structure were obtained.Mossbauer studies have shown that the Neel temperature T_(N) concentration dependences of the systems studied are in good agreement with T_(N)(x)calculated under the assumption of the ordered distribution of Fe^(3+)and nonmagnetic Sb^(5+)ions in the lattice.The T_(N) values obtained for BFO-xBFN and BFO-xPFS are close to the values,calculated for cases of the disordered and ordered distribution of Fe^(3+)and nonmagnetic Nb^(5+)and Sb^(5+)ions in the latice,respectively.The T_(N) values of BFO-xSFN and BFO-xSFS are in the range between the calculated values for ordered and disordered cases.Moreover the anomaly on the T_(N)(x)dependence for the BFO-xBFN and BFO-xSFN systems was found near x=0.7.This anomaly is most likely related to the destruction of the magnetic super exchange via the empty 6p state of Bi^(3+)ions.展开更多
X-ray absorption near-edge structure(XANES)spectra are the fingerprint of the local atomic and electronic structures around the absorbing atom.However,the quantitative analysis of these spectra is not straightforward....X-ray absorption near-edge structure(XANES)spectra are the fingerprint of the local atomic and electronic structures around the absorbing atom.However,the quantitative analysis of these spectra is not straightforward.Even with the most recent advances in this area,for a given spectrum,it is not clear a priori which structural parameters can be refined and how uncertainties should be estimated.Here,we present an alternative concept for the analysis of XANES spectra,which is based on machine learning algorithms and establishes the relationship between intuitive descriptors of spectra,such as edge position,intensities,positions,and curvatures of minima and maxima on the one hand,and those related to the local atomic and electronic structure which are the coordination numbers,bond distances and angles and oxidation state on the other hand.This approach overcoms the problem of the systematic difference between theoretical and experimental spectra.Furthermore,the numerical relations can be expressed in analytical formulas providing a simple and fast tool to extract structural parameters based on the spectral shape.The methodology was successfully applied to experimental data for the multicomponent Fe:SiO_(2)system and reference iron compounds,demonstrating the high prediction quality for both the theoretical validation sets and experimental data.展开更多
synthesisCeramic samples of BiFeO_(3)-based perovskite solid solutions with the highly ordered complex perovskites PbFe_(1/2)Sb_(1/2)O_(3)(PFS)and SrFe_(1/2)Sb_(1/2)O_(3)(SFS)were obtained using high-pressure synthesi...synthesisCeramic samples of BiFeO_(3)-based perovskite solid solutions with the highly ordered complex perovskites PbFe_(1/2)Sb_(1/2)O_(3)(PFS)and SrFe_(1/2)Sb_(1/2)O_(3)(SFS)were obtained using high-pressure synthesis at 4-6 GPa.Mössbauer studies revealed that BiFeO_(3)-SFS compositions are characterized by a larger compositional inhomogeneity as compared to BiFeO_(3)-PFS ones.In line with this result,concentration dependence of the magnetic phase transition temperature TN for BiFeO_(3)-SFS compositions is close to the TN(x)dependence for BiFeO_(3)solid solution with disordered perovskite PbFe_(1/2)Nb_(1/2)O_(3)(PFN).In contrast to this TN(x)dependence for BiFeO_(3)-PFS compositions nicely follows the theoretical TN(x)dependence calculated for the case of the ordered distribution of Fe3+and non-magnetic Sb^(5)+ions in the lattice(chemical ordering).展开更多
The comparative analysis of the dielectric properties of bismuth-containing pyrochlores with different manifestation of atomic order/disorder was carried out.We examined the dielectric properties(including behavior in...The comparative analysis of the dielectric properties of bismuth-containing pyrochlores with different manifestation of atomic order/disorder was carried out.We 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 structure.The fundamental differences between the dielectric properties of the BZN ceramics and Bi_(2)Ti_(2)O_(7)single crystal were shown.In 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.展开更多
0.5AFeO_(3)-0.5NaNbO_(3)(A=Bi,La)solid solution compositions were prepared using a solid phase reaction route from high-purity starting oxides.Mossbauer studies have shown that while for 0.5BiFeO_(3)-0.5NaNbO_(3)the m...0.5AFeO_(3)-0.5NaNbO_(3)(A=Bi,La)solid solution compositions were prepared using a solid phase reaction route from high-purity starting oxides.Mossbauer studies have shown that while for 0.5BiFeO_(3)-0.5NaNbO_(3)the magnetic phase transition temperature T_(M) value is about 150 K,for 0.5LaFeO_(3)-0.5NaNbO_(3),it is only≈25 K.This dramatic difference in T_(M) values seems to be due to additional contribution of the magnetic superexchange between Fe^(3+)ions via the empty 6p-states of Bi^(3+)ions to the overall superexchange.展开更多
This paper studies the dielectric spectra of solid solutions(SS)of the system(1−x−y)NaNbO_(3)-xKNbO_(3)-yCdNb_(2)O_(6) y=0.075,x=0.05÷0.30 in the temperature range(10÷900)K.The formation of a local maximum w...This paper studies the dielectric spectra of solid solutions(SS)of the system(1−x−y)NaNbO_(3)-xKNbO_(3)-yCdNb_(2)O_(6) y=0.075,x=0.05÷0.30 in the temperature range(10÷900)K.The formation of a local maximum was established in the interval(260÷300)K at small x values,which,as KNbO3 increases,is gradually blurred and becomes an inflection point.Detected in SS with x=0.05÷0.10,the shift of the maxima of dependencesε′/ε_(0)(T)andε″/ε_(0)(T),depending on the frequency of the electric field at the temperature ranges(300÷304)K and(258÷271)K,is not related to relaxation.This anomaly may indicate a crystallographic disorder to A and B positions.The conclusion is made about the expediency of using the obtained results for the development of functional ferroactive materials.展开更多
基金supported by the Russian Science Foundation(Grant No.23-42-10024)the Belarusian Republican Foundationfor Fundamental Researches(Grant No.T23RNF-086).
文摘Ceramic samples of(1-x)BiFeO_(3)-xPbFe_(0.5)Sb_(0.5)O_(3)(BFO-xPFS),(1-x)BiFeO_(3)-xSrFe_(0.5) Sb_(0.5)O_(3)(BFO-xSFS)where(x=0.05,0.1,..,0.9),(1-x)BiFeO_(3)-xBaFe_(0.5)Nb_(0.5)O_(3)(BFO-xBFN)and(1-x)BiFeO_(3)-xSrFe_(0.5)Nb_(0.5)O_(3)(BFO-xSFN)where(x=0,0.01,0.02,..,0.1,0.2,...,1)solid solutions with a perovskite structure were obtained.Mossbauer studies have shown that the Neel temperature T_(N) concentration dependences of the systems studied are in good agreement with T_(N)(x)calculated under the assumption of the ordered distribution of Fe^(3+)and nonmagnetic Sb^(5+)ions in the lattice.The T_(N) values obtained for BFO-xBFN and BFO-xPFS are close to the values,calculated for cases of the disordered and ordered distribution of Fe^(3+)and nonmagnetic Nb^(5+)and Sb^(5+)ions in the latice,respectively.The T_(N) values of BFO-xSFN and BFO-xSFS are in the range between the calculated values for ordered and disordered cases.Moreover the anomaly on the T_(N)(x)dependence for the BFO-xBFN and BFO-xSFN systems was found near x=0.7.This anomaly is most likely related to the destruction of the magnetic super exchange via the empty 6p state of Bi^(3+)ions.
基金A.Guda acknowledges the financial support from the Russian Foundation for Basic Research(project number 20-32-70227)for the work on the multicomponent mixtures.A.Bugaev and A.V.Soldatov acknowledge the Russian Science Foundation grant#20-43-01015 for the financial support for the work on the spectral descriptors.Authors acknowledge D.D.Badyukov from Vernadsky Institute of Geochemistry and Analytical Chemistry of Russian Academy of Sciences for providing samples for analysis.P.Šot acknowledges the Shell Global Solutions International,B.V.for funding the work on the synthesis of Fe-containing catalyst,and European Synchrotron Research Facility for awarded beamtimes at beamlines ID26,BM25,and Swiss Light Source for the beamtime at SuperXAS beamline.
文摘X-ray absorption near-edge structure(XANES)spectra are the fingerprint of the local atomic and electronic structures around the absorbing atom.However,the quantitative analysis of these spectra is not straightforward.Even with the most recent advances in this area,for a given spectrum,it is not clear a priori which structural parameters can be refined and how uncertainties should be estimated.Here,we present an alternative concept for the analysis of XANES spectra,which is based on machine learning algorithms and establishes the relationship between intuitive descriptors of spectra,such as edge position,intensities,positions,and curvatures of minima and maxima on the one hand,and those related to the local atomic and electronic structure which are the coordination numbers,bond distances and angles and oxidation state on the other hand.This approach overcoms the problem of the systematic difference between theoretical and experimental spectra.Furthermore,the numerical relations can be expressed in analytical formulas providing a simple and fast tool to extract structural parameters based on the spectral shape.The methodology was successfully applied to experimental data for the multicomponent Fe:SiO_(2)system and reference iron compounds,demonstrating the high prediction quality for both the theoretical validation sets and experimental data.
基金The reported study was funded by RFBR(Project number 20-52-00045)BRFBR(Project number T20R-169).
文摘synthesisCeramic samples of BiFeO_(3)-based perovskite solid solutions with the highly ordered complex perovskites PbFe_(1/2)Sb_(1/2)O_(3)(PFS)and SrFe_(1/2)Sb_(1/2)O_(3)(SFS)were obtained using high-pressure synthesis at 4-6 GPa.Mössbauer studies revealed that BiFeO_(3)-SFS compositions are characterized by a larger compositional inhomogeneity as compared to BiFeO_(3)-PFS ones.In line with this result,concentration dependence of the magnetic phase transition temperature TN for BiFeO_(3)-SFS compositions is close to the TN(x)dependence for BiFeO_(3)solid solution with disordered perovskite PbFe_(1/2)Nb_(1/2)O_(3)(PFN).In contrast to this TN(x)dependence for BiFeO_(3)-PFS compositions nicely follows the theoretical TN(x)dependence calculated for the case of the ordered distribution of Fe3+and non-magnetic Sb^(5)+ions in the lattice(chemical ordering).
基金The authors are grateful to L.A.Shilkina for X-ray phase analysis of the BZN samples.The reported study was funded by Russian Science Foundation(RSF)-research projects no.20-72-00086(BZN ceramics preparation,dielectric mea-surements)At RTU MIREA,the work was supported by the Ministry of Science and Higher Education of Russia(project FSFZ 0706-2020-2022,Bi2Ti2O7 single crystal growth),the equipment of the Center for Collective Use of RTU MIREA was used.
文摘The comparative analysis of the dielectric properties of bismuth-containing pyrochlores with different manifestation of atomic order/disorder was carried out.We 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 structure.The fundamental differences between the dielectric properties of the BZN ceramics and Bi_(2)Ti_(2)O_(7)single crystal were shown.In 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.
基金This work was supported by RFBR and NSFC,project 19-52-53030 GFEN a and by the Ministry of Education and Science of the Russian Federation(State assignment in the field of scientific activity,Southern Federal University,2020).
文摘0.5AFeO_(3)-0.5NaNbO_(3)(A=Bi,La)solid solution compositions were prepared using a solid phase reaction route from high-purity starting oxides.Mossbauer studies have shown that while for 0.5BiFeO_(3)-0.5NaNbO_(3)the magnetic phase transition temperature T_(M) value is about 150 K,for 0.5LaFeO_(3)-0.5NaNbO_(3),it is only≈25 K.This dramatic difference in T_(M) values seems to be due to additional contribution of the magnetic superexchange between Fe^(3+)ions via the empty 6p-states of Bi^(3+)ions to the overall superexchange.
基金The research was supported by the Strategic Academic Leadership Program of the Southern Federal University(“Priority 2030”)This report is presented at the 10th Anniversary International Conference on“Physics and Mechanics of New Materials and Their Applications”(PHENMA 2021),Divnomorsk,Russia,May 23-27,2022.
文摘This paper studies the dielectric spectra of solid solutions(SS)of the system(1−x−y)NaNbO_(3)-xKNbO_(3)-yCdNb_(2)O_(6) y=0.075,x=0.05÷0.30 in the temperature range(10÷900)K.The formation of a local maximum was established in the interval(260÷300)K at small x values,which,as KNbO3 increases,is gradually blurred and becomes an inflection point.Detected in SS with x=0.05÷0.10,the shift of the maxima of dependencesε′/ε_(0)(T)andε″/ε_(0)(T),depending on the frequency of the electric field at the temperature ranges(300÷304)K and(258÷271)K,is not related to relaxation.This anomaly may indicate a crystallographic disorder to A and B positions.The conclusion is made about the expediency of using the obtained results for the development of functional ferroactive materials.
