Query: A divalent rare earth oxide semiconductor: Yttrium monoxide

Candidate papers:

abstract: Rare earth oxides are usually widegap insulators like Y2O3 with closed shell trivalent rare earth ions. In this study, solid phase rock salt structure yttrium monoxide, YO, with unusual valence of Y2+ (4d1) was synthesized in a form of epitaxial thin film by pulsed laser deposition method. YO has been recognized as gaseous phase in previous studies. In contrast with Y2O3, YO was dark brown colored and narrow gap semiconductor. The tunable electrical conductivity ranging from 10 1 to 103 O 1 cm 1 was attributed to the presence of oxygen vacancies serving as electron donor. Weak antilocalization behavior observed in magnetoresistance indicated significant role of spin orbit coupling as a manifestation of 4d electron carrier.
author_names: Kenichi Kaminaga

Ryosuke Sei

Kouichi Hayashi

Naohisa Happo

Hiroo Tajiri

Daichi Oka

Tomoteru Fukumura

Tetsuya Hasegawa
title: A divalent rare earth oxide semiconductor: Yttrium monoxide
year: 2016

abstract: The recombination properties of silicon passivated with double layer dielectric films of yttrium oxide and dysprosium oxide have been investigated. The values of effective lifetime and surface recombination velocity of the nonequilibrium charge carriers on the interface of the rare earth elements/silicon oxide have been defined.
author_names: V A Rozhkov

M A Rodionov

A V Pashin

A M Guryanov
title: Passivation of the silicon semiconductor devices and microwave frequency attachments with the double layer dielectric films from yttrium oxide and dysprosium oxide
venue: 2004 14th International Crimean Conference "Microwave and Telecommunication Technology" (IEEE Cat. No.04EX843)
year: 2004

abstract: This paper reports an investigation of the electrophysical properties of metal dielectric semiconductor varicaps with an yttrium oxide dielectric, prepared by resistive vacuum evaporation of the rare earth metal with subsequent thermal oxidation of the film in air at 500 550 degC. It is found that the electrical conductivity of the samples follows the Poole Frenkel law. High frequency capacitance voltage characteristics are used to determine the specific capacitance of the dielectric, C0=0.027 0.03 mF/cm2, the slope of the capacitance voltage characteristic, dC/dV=35 40 pF/V, the fixed charge in the dielectric, Qf=(1.7 2.7)x10 8 C/cm2, and the density of surface states at the flat band potential, Nss=(1 2)x1011 cm 2*eV 1. The capacitance tuning range factor for the metal dielectric semiconductor varicaps is 2.5 3. These structures are shown to be applicable as metal dielectric semiconductor varicaps with a low control voltage and a high quality factor.
author_names: V A Rozhkov

A Yu Trusova
title: Silicon metal dielectric semiconductor varicaps with an yttrium oxide dielectric
year: 1997

abstract: Synchrotron radiation photoemission studies show that thin Yb overlayers (0.3 4.1) monolayers) enhance the oxidation of GaAs(110) surfaces. The magnitude of the promotion effect varies as a function of Yb coverage. The oxidation reaction products involve several nonequivalent oxidation states of As and Ga. The specific catalytic activity of the pure divalent Yb overlayers in promoting GaAs oxidation appears lower than that of Sm overlayers containing both Sm2+ and Sm3+ species. The spectroscopic signature of the oxidation reaction products, instead, is compellingly similar for the two rare earth promoters. We propose that the oxidation promotion mechanism is related, in both cases, to the decomposition of metal/semiconductor interface reaction products upon exposure to oxygen, and that the rare earth atomic valence has only a limited influence on the promotion mechanism.
author_names: S Chang

Pecoraro Raymond Philip

A Wall

X Yu

Alfonso Franciosi
title: Rare earth promoters of semiconductor oxidation: The case of GaAs(110)/Yb
year: 1990

abstract: Waste electrical and electronic equipment (WEEE) has increased in recent decades due to the continuous advancement of technology in the modern world. These residues have various metals that are found in concentrations that make their recovery profitable. A group of metals of interest are the rare earths such as europium and yttrium, as well as semiconductors such as indium. Yttrium was recovered from cathode ray tubes that were manually dismantled. The resulted powder was leached with HNO3, and then the solution was submitted to solvent extraction with di (2 ethylhexyl) phosphoric acid (DEHPA) using n heptane as a diluent. For re extraction, HNO3 was used again, and yttrium was precipitated by adding four times the stoichiometric amount of oxalic acid, reaching 68% yttrium purity. Indium was recovered from the liquid crystal display (LCD) screens for which the pulverized material was leached with H2SO4. Then, the indium sulfate was subjected to solvent extraction using DEHPA as an extractant, and diesel as a diluent. The re extraction was carried out again with H2SO4, and the obtained acid solution was evaporated until the indium precipitated, reaching a recovery of 95% The investigations that were carried out show that it is feasible to recover these metals in the form of oxides or phosphates with high commercial value.
author_names: Ernesto de la Torre

Estefania Vargas

Cesar A Ron

Sebastian Gamez
title: Europium, Yttrium, and Indium Recovery from Electronic Wastes
year: 2018

abstract: Solar energy represents an abundant (1000 W*m 2) and seemingly cheap source of energy. One way to tap it is to transform light into electricity with photovoltaic devices. Single junction solar cells presently reach 32% conversion yield under 1 sun illumination while multijunction devices irradiated by concentrated light can reach 44% One major problem encountered when trying to increase the conversion efficiency lies in the spectral mismatch between the absorption spectrum of the semiconductor and the solar emission spectrum. As a remedy, wavelength converting materials are being developed and because solar cells perform best in a relatively narrow spectral range which depends on their bandgap energy, lanthanide luminescent divalent and trivalent ions are particularly well suited for this purpose. In addition non luminescent ions feature special crystallographic and conduction properties which make them invaluable in lattice matched multijunction devices. In this chapter, the performances of rare earth ions in downconverting, downshifting, and upconverting materials embedded into the architecture of luminescent solar concentrators, silicon solar cells, semiconductor photovoltaic devices, and dye sensitized solar cells (DSSCs) is comprehensively and critically reviewed. Other contributions, e.g. as scattering layers and as modifiers of the bandgap of titanium oxide in DSSCs, or to the powering of in vivo nanorobots are likewise described. Finally a general assessment is made and improvements on the order of +5 absolute% in conversion yield are predicted provided fully optimized materials can be tailored.
author_names: Jean-Claude G Bunzli

Anne-Sophie Chauvin
title: Lanthanides in Solar Energy Conversion
year: 2014

abstract: Title of Document: EFFECTS OF COMPLEXATION WITH THE SIDEROPHORE DESFERRIOXAMINE B ON TRANSITION METAL REMOVAL FROM SEAWATER Emily A. Christenson, Master of Science, 2013 Directed By: Associate Professor, Johan Schijf, Marine Environmental and Estuarine Science Complexation of transition metals with strong organic ligands of unknown structure and origin plays an important role in their behavior and distributions in seawater. I present here a series of stability constants for complexes of several transition metals with the trihydroxamate siderophore desferrioxamine B (DFOB) representative of a class of small organic ligands that are exceptionally selective for Fe(III) and found in open ocean surface waters at low picomolar concentrations. Stability constants for DFOB complexes with divalent metals are similar to conditional constants that have been measured in seawater for highly metal specific, but unidentified organic ligands. Titration data indicate that free Hg forms a very stable complex with DFOB, however the more toxic methylmercury cation does not. A revised scavenging model for yttrium and the rare earth elements suggests that their removal from seawater is dominated by sorption onto Mn oxides, yet not significantly influenced by biogenic silica or calcite. EFFECTS OF COMPLEXATION WITH THE SIDEROPHORE DESFERRIOXAMINE B ON TRANSITION METAL REMOVAL FROM SEAWATER
author_names: Emily A Christenson
title: EFFECTS OF COMPLEXATION WITH THE SIDEROPHORE DESFERRIOXAMINE B ON TRANSITION METAL REMOVAL FROM SEAWATER
year: 2013

abstract: The crystal structure parameters of solid solutions YBaCuFe1 3 xCoxO5 (0 x 1) were determined, and their thermal stability, thermal expansion, conductance, thermoelectromotive force, dielectric properties, and magnetic sensibility were studied. At present, layered perovskite like oxides A`A"B2O5.5+d (A` is Y or rare earth element; A" is alkaline earth element; B is 3d metal) attract appreciable interest. One of such compounds is yttrium barium ferrocuprate YBaCuFeO5 d, which was described for the first time in [1] The compound YBaCuFeO5 has a tetragonal unit cell with the parameters a 0.3867 and c 0.7656 nm (space group P4mm, z 1) [2] though, according to [3] this compound belongs to space group P4/mmm. At room temperature, YBaCuFeO5 is antiferromagnetic (Neel temperature TN is 4403475 K) its magnetic structure changes at 1903240 K [335] (a commensurate 6 incommensurate phase transition) The compound YBaCuFeO5 is a p type semiconductor [6] and shows anomalies of dielectric properties near 460 and 560 K [7] The effect of iron replacement by nickel on the structure and properties of YBaCuFe13x NixO5 solid solutions was examined in [6] Solid solutions YBaCu13xCoxFeO5 +d, YBaCu13xFexFeO5 d, and YBaCuFe1 3 xCoxFeO5 d were obtained in [8] and their thermal stability in various gaseous media was examined in [9] Here we report data on the crystal structure, thermal expansion, and electrophysical and magnetic properties of solid solutions YBaCuFe1 3 xCoxO5.
author_names: Ekaterina A Chizhova

A I Klyndyuk

Leonid Bashkirov

Gennady Petrov

K I Yanushkevich
title: Structure and Properties of Solid Solutions in the System YBaCuFeO 5 YBaCuCoO 5
year: 2005

abstract: We report about the optical reflectivity of TmSeand of the metallic phase of SmS in the photon energy range between 0.03 eV and 12 eV. From the differentially measured lattice constants of both semiconducting and metallic SmS and from the plasma frequency, we deduce an intermediate Sm valence of 2.85 2.9 in the high pressure phase. 'Also in TmSe, we conclude from the plasma frequency the existence of about one delocalized electron per Tm ion. In the last few years, the discussion about mixed valence compounds opened a very interesting field of solid state physics [I] Although the concept of variable valence is well known in chemistry, it has extraordinary consequences in connection with Rare Earth (RE) elements and compounds and their physical properties. As is well known, many of the RE ions appear not only in the trivalent oxidation state, but also in the'divalent or tetravalent one, and the occupation number of the 4if shell changes concomitantly. In some compounds, the RE ions appear a priori in different valencies and the different valent ions can be situated on equivalent or inequivalent lattice sites. In the first case. the excess 4 f electrons of the lower valent cation move through the cation sublattice by means of a temperature activated hopping (Sm,S4, Eu,S, [2 41, at least above the charge ordering transition 5 and any cation experiences a fluctuating valence, whereas in the latter case the different valencies are static and regularly distributed (Eu,04, [6] But in this paper, we are dealing with a third group of mixed valence compounds, where every cation has a hybridized configuration in the form 4 fn 4 fn (5 d 6 s) It depends now only upon the hybridization energy relative to the energy differences between the various excited states involved in an experiment, whether one speaks of an intermediate valence [I] Assuming a typical hybridization energy of to lo eV e. g. a MBssbauer measurement (eV) shows an isomer shift corresponding to an intermediate valence, while photoemission (XPSor UPS) measurements (10 eV) detect a coexistence of two electronic configurations with integer number of 4 f electrons. One of the most important problems is to determine the degree of valence mixing. In principle, different methods seem to be appropriate, but every one has its own problems. For example, XPS and UPS compare the intensities of the typical 4 f multiplets in the energy distribution of emitted photoelectrons, while the Mossbauer effect and the method of the chemical shift of corelevels [7] measure spectral shifts. In the latter two procedures, a simple interpolation between the frequencies of non fluctuating ionic compounds yields the degree of mixing but covalency effects are rather difficult to estimate. An other easy way is the comparison of the measured lattice constant with the limiting values expected for pure valencies. This is based on the fact, that the ionic radii of different valent RE ions change up to 10 The validity is restricted by both principal and practical dificulties. First of all, a linear interpolation seems not to be suitable, because the potential energy distribution in general is not the same for different valent ions, moreover, the lattice constant is similarly influenced also by stoichiometry. In consequence of all these special pecularities it is desirable to have a further instrument at one's disposal to determine the degree of valence mixing. The hybridization between 4 fn and 4 fn (5 d 6 s) is equivalent to a partial delocalization of an electron, or in the language of the energy band theory, a change of the effective mass m* of the electron. The light electrons now are able to build up a common collective plasma oscillation, its frequency being given by the electron density and m* This coherent movement only arises, if the plasmon energy is larger than the hybridization energy. Thus, a measurable plasma resonance yields an Article published online by EDP Sciences and available at http:/dx.doi.org/10.1051/jphyscol:1976446 C4 268 B. BATLOGG, A. SCHLEGEL AND P. WACHTER upper limit for the hybridization energy together with the effective mass and the density of electrons. The effective optical mass can be determined for instance with cyclotron resonance measurements. SmS is at normal conditions a semiconductor with a narrow energy gap (0.1 eV) between the occupied and localized 4 f6 states and the 5 d conduction band. It crystallizes in the rock salt structure and Sm is divalent. Rising pressure increases the crystal field splitting of the 5 d conduction band, keeping the center of gravity constant [8] and an isostructural first order phase transition with typical hysteresis occurs [9, 101. The metallic high pressure phase has been the subject of many investigations and from lattice constant, specific heat [ll] susceptibility [I21 and Mossbauer isomer shift [13] an intermediate valence has been deduced. We obtain the golden, metallic phase by polishing black semiconducting crystals. Chemical analysis yields stoichiometry with a precision of 0.5 and a comparison of the room temperature electrical conductivity (37 R cm l) with systematic investigations of the el. conductivity as function of chemical composition [14] confirms the good quality of the samples used. The first experiment we have performed on such a black crystal with a 'golden surface, was a X ray Bragg reflection. Surprizingly, we found two sets of reflexes with equal line width and we computed lattice constants of 5.97 A and 5.68 A, corresponding doubtlessly to the semiconducting and the metallic phase. Moreover, this important result shows, that the surface is single crystalline and it supports our measurements as being representative for single crystals under hydrostatic pressure. This experiment has the additional advantage of every differential method and is free of calibration problems. Now we are able to estimate the degree of valence mixing using the new lattice constant of 5.68 A. In absence of a better way, also we interpolate linearly between the expected value of the Sm3'S and the known one of Sm2'S and obtain an intermediate valence of 2.85 for Sm. However, in a recent work on SmS films it is reported about the existence of SmS films with every lattice constant between 5.62 and 5.97 A [15] As mentioned above, the plasma resonance of the light electrons gives information about the degree of valence mixing. We have measured the reflectivity of the metallic phase of SmS in the photon energy range between 0.03 eV and 12 eV, and in function of temperature (4.2 K to 300 K) The spectrum in figure 1 behaves normal as known from Gdand La chalcogenides [I51 with interband transitions above 3 eV and plasma oscillation below 3 eV. On cooling to 4.2 K, the reflectivity edge, producing the golden colour, remains at the same energy and becomes only somewhat steeper as expected. In contrast, the reflectivity edge in chemically collapsed Sm, ,Yo ,S shifts toward lower energies with decreasing temperature [17] and this is the first decesive hint that chemical alloying is not equivalent to external mechanical FIG. 1. Optical reflectivity of metallic SmS at 300 K (full line) and at 4.2 K (dotted line) pressure alone. By means of a Kramers Kronig analysis, we derived the complex dielectric function 0 ie2(w) The real part increases from very large negative values at low energy and crosses the real axis at 2.45 eV. The positive slope of E, and a maximum in the energy loss function E E 8; at this energy (Fig. 2) indicate a longitudinal excitation mode, the coupled plasmon mode. The interaction between the free electrons is slightly screened by the presence of interband transitions and the unperturbed resonance will be shifted to higher energy. 0 2 4 6 Photon Energy (eV) FIG. 2. Energy loss function of metallic SmS and of TmSe. DEGREE OF VALENCE MIXING IN THE METALLIC PHASE OF SmS AND IN TmSe C4 269 With a procedure described elsewhere [18] we decompose 8, into contributions from bound 8' and free carriers 8: NOW, the intersection point of ef with the real axis at 4.6 eV gives the energy of the unperturbed plasma frequency o, of the conduction electrons. Because o, the density of carriers N and the effective mass m" are connected by we can immediately derive the number of light electrons per cation. Many other similarities in the electronic structure encourage us, to assume the same light effective mass in GdS (m* 1.3 m) 1161, because it is the same band with nearly the same degree of filling. Using the relation above, we obtain 0.9 electrons with m* 1.3 m per Sm and an intermediate valence of 2.9. The agreement with the value deduced from the differentially measured lattice constant is satisfactory. The intermediate valence of Sm in pure SmS, determinated on single crystalline samples with stoichiometric composition therefore is doubtless higher (2.85 2.9) than in chemically collapsed systems (2.7) Also the isomer shift measurements by Coey et al. [13] on high pressure SmS and on Smo.77Yo,,S clearly show a difference in the spectra and confirm, that chemical doping is not equivalent to external pressure
author_names: Bertram J Batlogg

A Schlegel

Peter Wachter
title: DEGREE OF VALENCE MIXING IN THE METALLIC PHASE OF SmS AND IN TmSe
year: 1976

abstract: In this study, we demonstrate that introducing of less electronegative R elements (R La or Pr) into the Bi O charge reservoir layer of BiCuSeO enhances the chemical bond ionicity and leads to an increase of both, the charge carrier concentration and the effective mass. Although the charge carrier mobility decreases upon Bi3+ to R3+ substitution, the electronic transport properties are significantly improved in a broad temperature range from 100 K to 800 K. In particular, the electrical resistivity decreases by two times, while the Seebeck coefficient drops from 323 mV K 1 to 238 mV K 1 at 800 K. Thus, a power factor of nearly 3 mW cm 1 K 2 is achieved for Bi0.92La0.08CuSeO sample at 800 K. Meanwhile, a noticeable decrease of the lattice thermal conductivity is observed for the doped samples, which can be attributed to the enhanced point defect scattering mostly originated from atomic mass fluctuations between R and Bi. Ultimately, a maximum zT value of nearly 0.34 at 800 K is obtained for the Bi0.92La0.08CuSeO sample, which is ~30% higher than that of pristine BiCuSeO. Introduction The oxyselenides family MCuSeO, where M trivalent cation such as Bi or rare earth elements, was reported for the first time in 1993 by Boris A. Popovkin group.1,2 The related compounds (so called 1111 phases) crystallize in the tetragonal layered ZrCuSiAs structure type with P4/nmm space group and two formula units per cell. The crystal structure is composed of alternately stacked along the c axis insulating (M2O2) layers with ionic bonds and conducting (Cu2Se2) layers with covalent bonds, as shown in Fig. 1a.1,3,4 Generally, the RCuSeO (R rare earth) are wide gap p type semiconductors (Eg ~3 eV) with the valence band maximum (VBM) and the conduction band minimum (CBM) at the G point of the Brillouin zone.5 8 In both cases, RCuSeO and BiCuSeO, the VBM is composed of the hybridized Cu 3d and Se 4p orbitals.9 BiCuSeO is also p type semiconductor, but with a narrow bandgap of about 0.8 eV. Such evolution in the band structure originates from the presence of Bi 6p orbitals at the bottom of the conduction band.5,10,11 To date, BiCuSeO oxyselenides have attracted considerable attention and were intensively studied as promising Pb free families of thermoelectric materials owing to their intrinsically low thermal conductivity and relatively high Seebeck coefficient. The remarkable thermoelectric performance was reported for Ba doped BiCuSeO with the dimensionless figure of merit zT value ~1.4 at 923 K.12,13 Here zT is defined as zT S2 s T k 1, where S, s, T and k are the Seebeck coefficient, electrical conductivity, absolute temperature, and total thermal conductivity, respectively.14,15 The charge carrier concentration in BiCuSeO can be increased using partial substitution of Bi3+ by divalent or monovalent ions inducing extra holes. However, the intrinsically low charge carrier mobility, which is usually below ~20 cm2 V 1 s 1 for pristine BiCuSeO, is deteriorated to less than 2 cm2 V 1 s 1 by heavy doping with alkali or alkaline earth elements, which greatly hampers the further possible electrical transport properties improvement.9 Thus, another strategy, such as band structure engineering along with tuning of chemical bonding is utilized to decouple the trade off between the charge carrier concentration and their mobility.16 19 The charge carries in BiCuSeO are predominantly scattered by acoustic phonons and thus their mobility is closely related to the effective mass and the carrierphonon coupling.20,21 At the same time, the effective mass, m* is largely determined by the ionicity (covalence) of the corresponding chemical bond. Since the electronegativity reflects the tendency of an atom to attract an electron density, the increase in bond ionicity will decrease the overlapping of the shared electron densities leading to increased effective mass. Furthermore, partial substitution of Bi by less electronegative atoms can lead to more electrons being released into the system, which may contribute to the enhanced charge carrier concentration. Besides, the Cu vacancies play an essential role in the BiCuSeO electrical transport and are believed to be the origin of the p type conduction in the nominally undoped BiCuSeO.9,10,22 Indeed, it was reported that the copper vacancies seem to be thermodynamically favored due to their low formation energy23 26 relative to other types of intrinsic defects, which results in unintentional doping of nominally undoped MCuSeO based compounds due to the presence of a faint amount of copper vacancies5,11,27 according to Kroger Vink notation:28 X 0 Cu Cu surface Cu Cu V h (1) Thus, the charge carrier concentration and the related electrical conductivity values strongly depend on the precise chemical composition, especially on the presence a National University of Science and Technology MISIS, 119049 Moscow, Russia b Ioffe Institute, 194021 St. Petersburg, Russia E mail: novitskiy@misis.ru c The University of New South Wales, 2052 Sydney, Australia d Sobolev Institute of Geology and Mineralogy, 630090 Novosibirsk, Russia e L.N. Gumilyov Eurasian National University, 010000 Nur Sultan, Kazakhstan Present address: Lulea University of Technology, 97187 Lulea, Sweden Electronic Supplementary Information (ESI) available PREPRINT Novitskii et al. April 21, 2021 2 of vacancies, and can vary from ~0.1 O 1 cm 1 to more than 1 O 1 cm 1 at room temperature and exhibit degenerate as well as nondegenerate behavior with temperature.10,11,23,27,29 32 Here we demonstrate experimentally that the carrier concentration and effective mass can be noticeably increased by doping with less electronegative rare earth elements (La or Pr) at the Bi site in (Bi2O2) layers. Consequently, a maximum zT of ~0.34 at 800 K can be achieved for the Bi0.92La0.08CuSeO sample, ~30% enhancement as compared with that of the pristine sample. The experimental study was combined with ab initio density functional theory (DFT) calculations in order to clarify the effect of band structure evolution with doping on transport properties. Experimental details The starting chemicals for the synthesis of Bi1 xRxCuSeO (R La or Pr, x 0 0.08) were the fine commercial powders of Bi2O3 (99.5% Reachem) La2O3 (99.99% Rare Metallic) Pr2O3 (99.99% Shin Etsu Chemical) and Bi 99.95% Component Reaktiv) Se (99.90% Reachem) Cu 99.5% Rushim) The powders were weighed, according to the stoichiometric ratio, and then ball milled (BM) in an argon atmosphere at 400 rpm for 8 hours (planetary micro mill Pulverisette 7 premium line, Fritsch, Germany) The obtained mixture was coldpressed into pellets and sealed in an evacuated to 10 3 Torr silica tubes. The tubes were heated to 573 K with the rate of 5 K min 1 and held for 8 hours, then cooled to room temperature. The resulting specimens were crushed, ground, and ball milled again in argon at 400 rpm for 4 hours, cold pressed, and resealed in another evacuated quartz tubes. The samples were annealed at 973 K for 12 hours. The pellets were ball milled one more time in argon at 300 rpm for 8 hours. For ball milling processing, the zirconium oxide vials with a volume of 45 ml and balls with a diameter of 5 mm were used. In order to obtain bulk samples, the powders were densified by spark plasma sintering (Labox 650, Sinter Land, Japan) at 973 K for 5 minutes under uniaxial pressure of 50 MPa. The cylindrical specimens of 12.7 mm in diameter and 10 mm high were annealed at 973 K for 6 hours in an argon atmosphere. For comparative analysis, one pristine BiCuSeO sample was prepared without using the ball milling during powder preparation, with hand grinding instead. More details on the experimental procedure can be found in the electronic supporting information file (ESI) The synthesized samples were characterized by a range of techniques, including X ray fluorescence (XRF) powder X ray diffraction (XRD) scanning electron microscopy (SEM) energy dispersive X ray spectroscopy (EDS) Brunauere Emmette Teller (BET) surface area analysis, and various physical measurements, such as the electrical and thermal conductivities, Seebeck coefficient and Hall constant measurements. The effective average particle size of the synthesized powders was calculated as D 6d 1 A 1 (where d is the density) from the low temperature adsorption isotherm measurements of the specific surface area, A, using a Nova 1200e analyzer (Quantachrome Instruments, USA) The XRF spectra were taken with a ZSK Primus II spectrometer (Rigaku, Japan) X ray diffraction data were collected over the angular range 20 2th (deg) 80, on a Miniflex 600 2 diffractometer (Rigaku, Japan) using CoKa radiation (l 1.7903 A) at room temperature. Rietveld refinement was performed using PDXL software (Rigaku, Japan) SEM and EDS were performed using Vega 3SB scanning electron microscope (Tescan, Czech Republic) in conjunction with an EDS detector (x act, Oxford Instruments, UK) Temperature dependencies of the electrical resistivity and the Seebeck coefficient were simultaneously measured with high resolution (temperature increment ~1 K) by the standard 4 probe and differential methods, respectively, under He atmosphere using a homemade system.33 The uncertainty of the Seebeck coefficient and the electrical resistivity measurements is 5% 0.5 mV/K and 2% respectively. Thermal conductivity, k, was determined from thermal Figure 1. (a) Crystal structure of the BiCuSeO and (b) XRD patterns of the Bi1 xRxCuSeO (R La or Pr, x 0 0.08) +Pristine BiCuSeO sample prepared without ball milling. PREPRINT Novitskii et al. April 21, 2021 3 diffusivity measurements using relationship k kh*Cp*d, where kh is the thermal diffusivity coefficient, Cp is the specific heat capacity. The relative bulk density was measured by the Archimedes method. Temperature dependencies of the thermal diffusivity were measured by the laser flash diffusivity metho
author_names: Andrei Novitskii

Illia Serhiienko

Sergey Novikov

Ye Zh Ashim

Mark V Zheleznyi

Kirill Kuskov

Daria Pankratova

P P Konstantinov

Andrei Voronin

Oleg A Tretiakov

Talgat M Inerbaev

A Burkov

Vladimir V Khovaylo
title: Tailoring the transport properties of BiCuSeO oxyselenides by increasing bond ionicity
year: 2021