Contraction Of Unit Cell Volume Research Articles

Effect of Bi doping in tuning the structural, morphological and optoelectronic properties of solvothermally synthesized SnS nanorods

In this work, enhanced optoelectronic properties of SnS is attained through the substitutional doping of Bi into the SnS lattice at the ‘Sn’ sites by following cost effective solvothermal method at a reaction temperature of 170 °C for a duration of 90 min. The charge states explored through XPS analysis revealed the existence of the constituent elements in Sn2+, S-Sn2+ and Bi3+ states. The chemical structure investigated through Raman analysis revealed the successful doping of Bi into orthorhombic SnS without affecting its phase purity for doping up to 12 %. With increasing the doping up to 4 %, (a) the shift in 2θ peak position to the higher angle side and the contraction in unit cell volume as evident from XRD analysis ensured the substitutional doping of Bi3+ into Sn2+ sites and (b) the direct energy band gap and electrical resistivity are reduced from 1.60 to 1.30 eV and 719×103 to 627×102 Ω cm respectively and the carrier concentration is enhanced from 1.22×1012 to 8.92×1013 cm−3 revealing the optimum doping of Bi into SnS is 4 %. Due to the effect of doping, the homogeneity in size and shape of the nanorods is enhanced with an increase in size as evident from HR-TEM analysis. The electrical transport properties obtained from Hall measurement studies showed p-type conductivity for SnS with Bi doping up to 10 %. Hence, this report provides the first experimental confirmation for the absence of any carrier polarity conversion in phase pure SnS due to the incorporation of Bi.

Pressure-induced Yb valence transition and magnetism in YbMn6Ge6−xSnx

We investigate the external pressure dependence of the crystal structure, Yb valence, and local magnetization in ${\mathrm{YbMn}}_{6}{\mathrm{Ge}}_{6\ensuremath{-}x}{\mathrm{Sn}}_{x}$ using x-ray diffraction, x-ray absorption near edge spectroscopy (XANES), and x-ray magnetic circular dichroism (XMCD). The application of physical pressure results in a weakly anisotropic unit cell volume contraction without modifying the crystal structure. The external pressure allows crossing the Yb magnetic instability, which occurs for strongly hybridized Yb (valence $\ensuremath{\approx}2.76$), with a concomitant slope change in the valence-pressure curve. In the Ge-rich compounds, Yb local magnetism vanishes at very high pressure ($P \ensuremath{\ge}39.8$ GPa) likely because of the simultaneous collapse of the Mn magnetism. The results underline similarities between external and chemical pressure increase, which favors trivalent and magnetic Yb. Some differences are observed in the Sn-rich compounds highlighting potential local pressure and/or electronic effects.

Stepwise dehydration of thomsonite (THO) with disordered Si/Al distribution: A new partially hydrated phase

The structural transformations occurring as a function of increasing temperature in zeolites are of interest because the porous structure, and therefore the physical properties, can significantly change.Zeolites with THO framework type are small-pore materials, which received attention because of their applications in catalytic processes. The majority of THO zeolites (synthetic and natural) are characterized by an ordered distribution of the cations at the tetrahedral sites. To date, few cases of disordered thomsonite have been reported. In this study, we investigated the dehydration behaviour of a natural thomsonite with disordered Si/Al distribution and chemical composition Ca3·34Na2·66Si11Al9O40∙12H2O. The structure was determined from room temperature (RT) to 698 K in order to compare the thermal behaviour with that reported for the ordered variety. Accurate structural analysis was performed by in situ single crystal X-ray diffraction. The dehydration starts at 348 K. Up to 498 K, thomsonite gradually releases four H2O. From 498 to 573 K, additional four H2O are lost and the space group changes from orthorhombic (Pbmn) to monoclinic (P21/n). This partially hydrated phase is characterized by a unit-cell volume contraction of −3% with respect to the RT phase and by a rearrangement of the extraframework cations in the zeolitic pores. The thermally treated thomsonite is able to reabsorb 50% of the lost H2O and transforms to the orthorhombic phase, equivalent to that observed at lower temperatures. However, the diffraction pattern analysis indicated a high degree of mosaicity, most probably due to the residual stress accumulated during the phase transformation.

Enhancing the thermoelectric properties of CaMnO3-δ via optimal substituent selection

The interplay of crystal structure and thermoelectric properties of A- or B-site substituted high-density calcium manganese oxide ceramics, Ca1-zAzMn1-zMzO3-δ (A ​= ​Bi, Gd, Yb/Gd or M ​= ​W with 0 ≤ z ​≤ ​0.08) is investigated. For the same degree of substitution z, smaller sized substituents cause a unit cell volume contraction and higher electrical conductivity, whereas the Seebeck coefficients are not affected. Evaluation along with results from published reports shows that this is valid for both, A- and B-site substitutions. The mean tolerance factor is used to describe this dependency qualitatively. The high-density ceramics show large power factors (S2σ ​> ​400 ​μW/mK2) and moderate figures of merit zT ​≈ ​0.15 ​at 700 ​°C. The best thermoelectric performance is anticipated for calcium manganese oxide, substituted heterovalently as well as homovalently with small substituents, due to higher electrical conductivity and lower thermal conductivity.

The Nature of the Atypical Kinetic Effects Observed for the Thermally Induced Spin Transition in Ferrous Nitroprussides with Short Organic Pillars

AbstractIn pillared 2D ferrous nitroprussides, Fe(L)x[Fe(CN)5NO] where x=1, 2, and L is an appropriate organic molecule, the axial CN and NO groups are dangling ligands found in the interlayer region. These ligands subtract electron density from the iron atom in the nitroprusside building block via π‐back bonding interaction. That electron density appears accumulated at their CN5σ and NOπ* orbitals, and for the case of short pilar molecules, such electron density is responsible for the appearance of a repulsive force between adjacent layers. In the series of ferrous nitroprussides with short pillar molecules herein considered (L=pyrazine, pyridine, and 4‐methylpyridine), that repulsive electrostatic interaction opposes the unit cell volume contraction during the spin transition (HS→LS) on the sample cooling and it favors the cell expansion that accompanies the inverse spin transition (LS→HS) when the sample is warmed. This results in an atypical kinetic behavior for the thermally induced spin transition in these materials. The lower the scan rate, the greater the shift of the HS→LS transition towards low temperatures. The features of this effect are herein discussed. For a large pillar molecule, e. g. 4,4'‐azopyridine, or in the absence of that electrostatic interaction, for instance, in Fe(Pyz)[Pt(CN)4] where Pyz=pyrazine, such an atypical effect is not observed. The results discussed in this contribution illustrate how relevant could be the structural factors on the spin crossover (SCO) in coordination polymers. This study includes an evaluation of the effects of repeated cycles of cooling and warming on the recorded magnetic data, considering that the spin transitions involve nucleation and growth processes of the solid crystallites and structural changes within the solid framework.

Large magnetoresistance and magnetostrain in the batch-processed (Mn2Sb)1-xBix crystals (x = 0.06, 0.08, 0.10, 0.12)

We investigate the effects of Bi substitution on the structure, magnetization, magnetoresistance, and magnetostrain in single crystals of (Mn2Sb)1-xBix (x = 0.06, 0.08, 0.1, and 0.12). It is found that the element Bi can be partially substituted for Sb in the tetragonal Mn2Sb main phase, and partially forms the MnBi and Bi-rich secondary phases. The introduction of Bi causes the simultaneous lattice shrinkages in a and c for the main phase, and also enhances the transition temperature of the first-order magnetoelastic ferrimagnetic-antiferromagnetic transition. Such an enhancement in transition temperature due to contraction of the unit-cell volume contraction is also experimentally proven based on the thermomagnetic curves under hydrostatic pressure for a crystal with × = 0.12. The volume contraction rate due to hydrostatic pressure is deduced to be −0.0386 Å3/GPa. Moreover, the highest values of in-plane magnetoresistance (∼-30%) and magnetostrain (∼−1448 ppm) with good reversibility are attained at 120 K under 30 kOe, which was proven to be the optimal magnetic field. Our experimental results show that Mn2Sb-based intermetallic compounds can be considered promising candidates for low-cost, multifunctional magnetic materials.

Elucidating Cathode Degradation Mechanisms in LiNi0.8Mn0.1Co0.1O2 (NMC811)/Graphite Cells Under Fast Charge Rates Using Operando Synchrotron Characterization

Li-ion batteries capable of extreme fast charging (XFC) are in demand to facilitate widespread electric vehicle (EV) adoption. While the impact of fast charge on the negative electrode has been studied, degradation of state-of-the-art NMC811 under XFC conditions has not been studied in detail. Herein, cathode degradation is probed in NMC811/graphite batteries by analysis of structural and chemical changes for recovered samples previously cycled under XFC conditions and during typical cycling. NMC surface reconstruction, as determined by soft X-ray absorption, was not detected for recovered electrodes. However, bulk redox activity from X-ray absorption near edge structure measurements showed more change in the oxidation state of Ni and Co under the 1C charge rate compared to the 4C rate consistent with the electrochemistry. Increased unit cell volume contraction under the 1C rate as determined by operando X-ray diffraction suggests that higher charge rates may provide a protective effect on the cathode by reducing structural distortion due to less delithiation.

Structural Evolution of Ag-LEV Zeolite upon Heating: An In Situ Single-Crystal X-ray Diffraction (SC-XRD) and X-ray Absorption Spectroscopy (XAS) Study.

Ag-exchanged zeolites are known to have improved sorption and catalytic properties compared to the raw natural material. The application range of Ag-exchanged zeolites is linked to the stability of the exchanged form and its structural evolution at high temperatures. In this study, we investigated the thermal stability of a Ag-exchanged zeolite with an LEV framework type. The dehydration path was monitored in situ by single-crystal X-ray diffraction (SC-XRD) and X-ray absorption fine structure spectroscopy (XAFS). The experimental data were compared with those extrapolated from molecular dynamics (MD) trajectories. Our results showed that Ag-exchanged levyne (Ag-LEV) follows a different dehydration path compared to that of the natural levyne (Ca-LEV). Between 25 and 350 °C, the unit cell volume contraction was −4% with respect to that measured at room temperature. Upon dehydration, Ag-LEV transformed to the LEV B topology: such transformation is accompanied by the change from R3̅m to R3m space group and by the onset of the rupture of one T–O–T connection at 250 °C. Differently from Ca-LEV, no additional change to LEV B′ configuration was detected. XAFS analysis indicated that each Ag is approximately surrounded by four oxygen atoms between 2.15 and 2.40 Å. This local environment was maintained up to 650 °C. Weak Ag+1–Ag+1 interactions, detected in the whole investigated temperature range, are mainly ascribed to the presence of Ag-erionite (Ag-ERI) intergrown with Ag-LEV. No reduction to elemental Ag0 occurred upon heating.

Synthesis and Polymorphism of Mixed Aluminum-Gallium Oxides.

The synthesis of a new solid solution of the oxyhydroxide Ga5–xAlxO7(OH) is investigated via solvothermal reaction between gallium acetylacetonate and aluminum isopropoxide in 1,4-butanediol at 240 °C. A limited compositional range of 0 ≤ x ≤ 1.5 is produced, with the hexagonal unit cell parameters refined from powder X-ray diffraction (XRD) showing a linear contraction in unit cell volume with an increase in Al content. Solid-state 27Al and 71Ga nuclear magnetic resonance (NMR) spectroscopies show a strong preference for Ga to occupy the tetrahedral sites and Al to occupy the octahedral sites. Using isopropanol as the solvent, γ-Ga2–xAlxO3 defect spinel solid solutions with x ≤ 1.8 can be prepared at 240 °C in 24 h. These materials are nanocrystalline, as evidenced by their broad diffraction profiles; however, the refined cubic lattice parameter shows a linear relationship with the Ga:Al content, and solid-state NMR spectroscopy again shows a preference for Al to occupy the octahedral sites. Thermal decomposition of Ga5–xAlxO7(OH) occurs via poorly ordered materials that resemble ε-Ga2–xAlxO3 and κ-Ga2–xAlxO3, but γ-Ga2–xAlxO3 transforms above 750 °C to monoclinic β-Ga2–xAlxO3 for 0 ≤ x ≤ 1.3 and to hexagonal α-Ga2–xAlxO3 for x = 1.8, with intermediate compositions of 1.3 < x < 1.8 giving mixtures of the α- and β-polymorphs. Solid-state NMR spectroscopy shows only the expected octahedral Al for α-Ga2–xAlxO3, and for β-Ga2–xAlxO3, the ∼1:2 tetrahedral:octahedral Al ratio is in good agreement with the results of Rietveld analysis of the average structures against powder XRD data. Relative energies calculated by periodic density functional theory confirm that there is an ∼5.2 kJ mol–1 penalty for tetrahedral rather than octahedral Al in Ga5–xAlxO7(OH), whereas this penalty is much smaller (∼2.0 kJ mol–1) for β-Ga2–xAlxO3, in good qualitative agreement with the experimental NMR spectra.

Co-Doped Rare-Earth (La, Pr) and Co-Al Substituted M-Type Strontium Hexaferrite: Structural, Magnetic, and Mossbauer Spectroscopy Study

The present study investigates the influence of La3+ and Pr3+ doping on the structural, magnetic properties, and hyperfine fields of Sr0.7RE0.3Fe12-2x CoxAlxO19, (RE: La3+ and Pr3+, x = 0.0 - 0.8) hexaferrite compounds prepared via auto-combustion technique. The XRD analysis shows a linear decrease in a and c lattice and unit cell volume contraction with the content x. The room temperature magnetic study shows that for the Pr3+ doped Sr0.7Pr0.3Fe12-2x CoxAlxO19 (Pr3+-SrM), the magnetization value monotonically decreases while for La3+ doped Sr0.7La0.3Fe12-2xCoxAlxO19 (La3+-SrM) magnetization value shows a noticeable increase in magnetization value with x. The coercivity of the Pr3+-SrM compound was observed to decrease while that of the La3+-SrM compound showed a marked 40% increase at x = 0.2 (~5829 Oe) in comparison to undoped SrFe12O19 (~3918 Oe). A difference in Curie temperature was also observed, with Tc ~ 525°C at x = 0.4 for Pr3+-SrM and Tc = 505°C for x = 0.4 for La3+-SrM compound. The observed differences in magnetic properties have been explained on the basis of the site occupancy of Co2+ and Al3+ in the presence of rare-earth ions. The presence of non-magnetic rare-earth ion, La3+, improved saturation magnetization, and coercivity and deemed suitable replacement for Sr2+. The hyperfine parameters namely quadrupole shift showed a decrease with the La3+ or Pr3+ doping independent of (Co2+-Al3+) ions doping. Overall, the Mossbauer analysis suggests that the (Co2+-Al3+) impurities prefer occupancy at 2a site.

Multicolour emission from thermally stable Tb3+/Eu3+ co-doped CaLa4Si3O13 phosphors for single-component w-LEDs application

Colour-tuneable Tb3+/Eu3+ co-doped CaLa4Si3O13 phosphors were prepared by a high-temperature solid-state reaction approach. The contraction of unit cell volume was concluded from the XRD Rietveld refinements data after introduction of dopants and suggests that the dopants have been effectively incorporated into the La3+ sites. Characteristic emission peaks at 545 and 617 nm originated from Tb3+ and Eu3+ emitting centres are observed under the excitation of 379 nm light. An adjustment of emission colour is achieved by varying the Eu3+ concentration. Energy transfer from Tb3+ to Eu3+ ions is experimentally confirmed from the photoluminescence and lifetime measurements. The dipole-dipole interaction is proposed as the main energy transfer route by Dexter's energy transfer formula and Inokuti-Hirayama model. The prepared phosphors exhibit good thermal stability at elevated temperatures. The results indicate that the synthesized materials have a great potential for single-component w-LED applications.

A Coherently Strained Monoclinic [111]PbTiO3 Film Exhibiting Zero Poisson's Ratio State

Abstract[111]‐Oriented perovskite oxide films exhibit unique interfacial and symmetry breaking effects, which are promising for novel quantum materials as topological insulators and polar metals. However, due to strong polar mismatch and complex structural reconstructions on (111) surfaces/interfaces, it is still challenging to grow high quality [111] perovskite heterostructures, let alone explore the as‐resultant physical properties. Here, the fabrication of ultrathin PbTiO3 films grown on a SrTiO3(111) substrate with atomically defined surfaces, by pulsed laser deposition, is reported. High‐resolution scanning transmission electron microscopy and X‐ray diffraction reveal that the as‐grown [111]PbTiO3 films are coherent with the substrate and compressively strained along all in‐plane directions. In contrast, the out‐of‐plane lattices are almost unchanged compared with that of bulk PbTiO3, resulting in a 4% contraction in unit cell volume and a nearly zero Poisson's ratio. Ferroelectric displacement mapping reveals a monoclinic distortion within the compressed [111]PbTiO3, with a polarization larger than 50 µC cm−2. The present findings, as further corroborated by phase field simulations and first principle calculations, differ significantly from the common [001]‐oriented films. Fabricating oxide films through [111] epitaxy may facilitate the formation of new phase components and exploration of novel physical properties for future electronic nanodevices.

Colossal Negative Thermal Expansion in Electron‐Doped PbVO3 Perovskites

AbstractColossal negative thermal expansion (NTE) with a volume contraction of about 8 %, the largest value reported so far for NTE materials, was observed in an electron‐doped giant tetragonal perovskite compound Pb1−xBixVO3 (x=0.2 and 0.3). A polar tetragonal (P4mm) to non‐polar cubic structural transition took place upon heating. The coefficient of thermal expansion (CTE) and the working temperature could be tuned by changing the Bi content, and La substitution decreased the transition temperature to room temperature. Pb0.76La0.04Bi0.20VO3 exhibited a unit cell volume contraction of 6.7 % from 200 K to 420 K. Interestingly, further gigantic NTE of about 8.5 % was observed in a dilametric measurement of a Pb0.76La0.04Bi0.20VO3 polycrystalline sample. The pronounced NTE in the sintered body should be attributed to an anisotropic lattice parameter change.

Colossal Negative Thermal Expansion in Electron-Doped PbVO3 Perovskites.

Colossal negative thermal expansion (NTE) with a volume contraction of about 8 %, the largest value reported so far for NTE materials, was observed in an electron-doped giant tetragonal perovskite compound Pb1-x Bix VO3 (x=0.2 and 0.3). A polar tetragonal (P4mm) to non-polar cubic structural transition took place upon heating. The coefficient of thermal expansion (CTE) and the working temperature could be tuned by changing the Bi content, and La substitution decreased the transition temperature to room temperature. Pb0.76 La0.04 Bi0.20 VO3 exhibited a unit cell volume contraction of 6.7 % from 200 K to 420 K. Interestingly, further gigantic NTE of about 8.5 % was observed in a dilametric measurement of a Pb0.76 La0.04 Bi0.20 VO3 polycrystalline sample. The pronounced NTE in the sintered body should be attributed to an anisotropic lattice parameter change.

Investigation of structural, optical, dielectric and magnetic studies of Mn substituted BiFeO3 multiferroics

Abstract A series of Mn doped BiFeO 3 with composition BiMn x Fe 1−x O 3 (x = 0.0, 0.025, 0.05, 0.075, 0.1) was synthesized via a citrate precursor method. Structural, morphological, optical, electrical and magnetic properties were investigated by using various measurement techniques. XRD patterns confirmed that the materials possess distorted rhombohedral structure with space group R 3 c . Average crystallite size was found to be in the range 18–36 nm. A decrease in the value of lattice parameters has been observed due to contraction of unit cell volume with Mn doping. Higher tensile strain for the prepared nanoparticles was observed in Hall-Williamson Plot. Field Emission Scanning Microscopy (FESEM) showed the spherical, uniform, dense nanoparticles in the range 80–200 nm. Reduction in grain size was observed which may be due to suppression of grain growth with Mn doping. FTIR studies reported two strong peaks at 552 cm −1 and 449 cm -1 which confirmed the pervoskite structure. Dielectric properties were studied by measuring the dielectric constant and loss in the frequency range 1 kHz to 1 MHz. Magnetic hysteresis loop showed the retentivity (M r ) increasing from 0.0514 emu/g of BFO to 0.0931 emu/g of 10% Mn doping. Coercivity was found to increase upto 0.0582 T for 5% Mn doping and then reduced to 0.0344 T for 7.5% Mn doping. Saturation magnetization was observed to increase from 0.6791 emu/g for BFO to 0.8025 emu/g for 7.5% and then reduced to 0.6725 emu/g for 10% Mn doping in BFO. Improvement in dielectric and magnetic properties makes this material as a promising candidate for multifunctional device applications.

Extreme Flexibility in a Zeolitic Imidazolate Framework: Porous to Dense Phase Transition in Desolvated ZIF-4.

Desolvated zeolitic imidazolate framework ZIF-4(Zn) undergoes a discontinuous porous to dense phase transition on cooling through 140 K, with a 23 % contraction in unit cell volume. The structure of the non-porous, low temperature phase was determined from synchrotron X-ray powder diffraction data and its density was found to be slightly less than that of the densest ZIF phase, ZIF-zni. The mechanism of the phase transition involves a cooperative rotation of imidazolate linkers resulting in isotropic framework contraction and pore space minimization. DFT calculations established the energy of the new structure relative to those of the room temperature phase and ZIF-zni, while DSC measurements indicate the entropic stabilization of the porous room temperature phase at temperatures above 140 K.

Extreme Flexibility in a Zeolitic Imidazolate Framework: Porous to Dense Phase Transition in Desolvated ZIF‐4

AbstractDesolvated zeolitic imidazolate framework ZIF‐4(Zn) undergoes a discontinuous porous to dense phase transition on cooling through 140 K, with a 23 % contraction in unit cell volume. The structure of the non‐porous, low temperature phase was determined from synchrotron X‐ray powder diffraction data and its density was found to be slightly less than that of the densest ZIF phase, ZIF‐zni. The mechanism of the phase transition involves a cooperative rotation of imidazolate linkers resulting in isotropic framework contraction and pore space minimization. DFT calculations established the energy of the new structure relative to those of the room temperature phase and ZIF‐zni, while DSC measurements indicate the entropic stabilization of the porous room temperature phase at temperatures above 140 K.

Interplay of chemical expansion, Yb valence, and low temperature thermoelectricity in the YbCu2Si2−xGex solid solution

YbCu2Si2 is a promising low temperature thermoelectric material because of the large broad peak in the Seebeck coefficient near 100 K combined with a low electrical resistivity. This behavior is thought to arise from fluctuating, or intermediate, valence effects due to partial occupation of Yb 4f energy states near the Fermi level. Previous studies of the magnetic properties under pressure have demonstrated that the average Yb valence is sensitive to the contraction of unit cell volume. By forming a solid solution of YbCu2Si2 with YbCu2Ge2, an isostructural compound with a larger unit cell volume, here we examine the subtle effects of lattice expansion on the transport properties and average Yb valence. We observe a shift in the peak of the Seebeck coefficient towards higher temperatures, as well as an enhanced power factor in the solid solutions. At the same time, a reduction in thermal conductivity due to alloy scattering enhances the thermoelectric figure of merit. Chemical pressure effects may thus be utilized to control and optimize the thermoelectric properties of these alloys in the cryogenic temperature range.

Effect of annealing temperatures on the structure and leakage mechanisms of BiFeO3 thin films prepared by the sol–gel method

In this paper, we report the fabrication of polycrystalline BiFeO3 (BFO) thin films on Pt(111)/Ti/SiO2/Si(100) substrates by the sol–gel method. The effect of annealing temperature (T a ) on the structural, optical, morphological, ferroelectric and leakage properties of the films were analyzed by X-ray diffraction (XRD), Raman spectroscopy, Atomic force microscope (AFM) and ferroelectric measurements. XRD patterns and micro-Raman spectra demonstrated that all films had a single perovskite-type rhombohedral structure. A distortion in crystal lattice constants and a contraction in unit cell volume were observed with the increase of annealing temperatures. AFM images showed that dense and uniform grains were obtained. This reveals that the film is well crystallized. The data of ferroelectric test indicated that the double remanent polarization (2P r ) value of the thin film at T a = 600 °C was 22 μC/cm2 and the leakage current density was 9.0 × 10−8 A/cm2 at an applied electric field of 1.0 × 105 V/cm. The leakage mechanisms of thin films have been studied in order to identify the cause of high leakage currents such as Ohmic conduction, the space-charge-limited current, the Schottky emission, the Fowler–Nordheim tunneling and the Poole–Frenkel emission. In low electric field region (<1.0 × 105 V/cm), the conduction behavior was found to be dominated by Ohmic conduction for the thin film annealed at 500 °C. The Ohmic conduction and space-charge-limited current dominated the leakage behavior for the thin films at T a = 550 and 600 °C. Fowler–Nordheim tunneling was responsible for the leakage behavior of the thin films at T a = 550, 600 °C in high electric field region (>1.0 × 105 V/cm). The results demonstrated that the microstructure, surface morphology and ferroelectric properties of BFO thin films have a strong dependence on annealing temperatures.

Synthesis of PdO‐ZnO mixed oxide precursors for PdZn intermetallic catalysts

PdZn mixed oxides are precursors for the formation of intermetallic PdZn phases, which show improved catalytic performance for methanol steam reforming. In this work we have prepared mixed oxides (PdxZn1‐xO) that span a range of compositions around the tetragonal PdZn 1:1 L10 phase (x = 0.25, 0.5 and 0.75). We find that Pd+2 can be isomorphously substituted into hexagonal ZnO and likewise Zn+2 can also be substituted within tetragonal PdO. Our results show that the mixed oxide has a composition Pd0.75Zn0.25O within the tetragonal PdO lattice with a slight contraction in unit cell volume. The results are relevant for understanding the enhanced sensing properties of ZnO and the nature of the oxide precursors for the synthesis of intermetallic PdZn nanoparticles for heterogeneous catalysis.