(De)lithiation of spinel ferrites Fe3O4, MgFe2O4, and ZnFe2O4: a combined spectroscopic, diffraction and theory study
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99 GENERAL AND MISCELLANEOUS↗
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Structural and electrochemical investigation of crystallite size controlled zinc ferrite (ZnFe2O4)
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99 GENERAL AND MISCELLANEOUS↗
Materials Data on ZnFe by Materials Project
ZnFe is Tetraauricupride structured and crystallizes in the tetragonal P4/mmm space group. The structure is three-dimensional. Fe is bonded to four equivalent Fe and eight equivalent Zn atoms to form FeZn8Fe4 cuboctahedra that share corners with twelve equivalent FeZn8Fe4 cuboctahedra, edges with eight equivalent FeZn8Fe4 cuboctahedra, edges with sixteen equivalent ZnZn4Fe8 cuboctahedra, faces with eight equivalent ZnZn4Fe8 cuboctahedra, and faces with ten equivalent FeZn8Fe4 cuboctahedra. All Fe–Fe bond lengths are 2.57 Å. All Fe–Zn bond lengths are 2.66 Å. Zn is bonded to eight equivalent Fe and four equivalent Zn atoms to form ZnZn4Fe8 cuboctahedra that share corners with twelve equivalent ZnZn4Fe8 cuboctahedra, edges with eight equivalent ZnZn4Fe8 cuboctahedra, edges with sixteen equivalent FeZn8Fe4 cuboctahedra, faces with eight equivalent FeZn8Fe4 cuboctahedra, and faces with ten equivalent ZnZn4Fe8 cuboctahedra. All Zn–Zn bond lengths are 2.57 Å.
36 MATERIALS SCIENCE↗
Direct Visualization of Magnetic Correlations in Frustrated Spinel ZnFe 2 O 4
Magnetic materials with the spinel structure (A 2+ B 3+ 2 O 4 ) form the core of numerous magnetic devices, and ZnFe 2 O 4 constitutes a peculiar example where the nature of the magnetism is still unresolved. Susceptibility measurements revealed a cusp around T c = 13 K resembling an antiferromagnetic transition, despite the positive Curie–Weiss temperature determined to be Θ CW = 102.8(1) K. Bifurcation of field-cooled and zero-field-cooled data below T c in conjunction with a frequency dependence of the peak position and a non-zero imaginary component below T c shows it is in fact associated with a spin-glass transition. Highly structured magnetic diffuse neutron scattering from single crystals develops between 50 K and 25 K revealing the presence of magnetic disorder which is correlated in nature. Here, the 3D-mΔPDF method is used to visualize the local magnetic ordering preferences, and ferromagnetic nearest-neighbor and antiferromagnetic third nearest-neighbor correlations are shown to be dominant. Their temperature dependence is extraordinary with some flipping in sign and a strongly varying correlation length. The correlations can be explained by orbital interaction mechanisms for the magnetic pathways and a preferred spin cluster. This study demonstrates the power of the 3D-mΔPDF method in visualizing complex quantum phenomena thereby providing a way to obtain an atomic-scale understanding of magnetic frustration.
36 MATERIALS SCIENCE↗
Materials Data on ZnFe(SiO3)2 by Materials Project
Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations
36 MATERIALS SCIENCE↗
Materials Data on ZnFe(Mo3S4)4 by Materials Project
FeZn(Mo3S4)4 crystallizes in the trigonal R-3 space group. The structure is three-dimensional. there are two inequivalent Mo+2.33+ sites. In the first Mo+2.33+ site, Mo+2.33+ is bonded to five S2- atoms to form a mixture of corner and edge-sharing MoS5 square pyramids. There are a spread of Mo–S bond distances ranging from 2.43–2.52 Å. In the second Mo+2.33+ site, Mo+2.33+ is bonded to five S2- atoms to form a mixture of corner and edge-sharing MoS5 square pyramids. There are a spread of Mo–S bond distances ranging from 2.44–2.50 Å. Fe2+ is bonded in a distorted linear geometry to eight S2- atoms. There are two shorter (2.26 Å) and six longer (3.18 Å) Fe–S bond lengths. Zn2+ is bonded in a distorted linear geometry to eight S2- atoms. There are two shorter (2.28 Å) and six longer (3.20 Å) Zn–S bond lengths. There are four inequivalent S2- sites. In the first S2- site, S2- is bonded in a 1-coordinate geometry to three equivalent Mo+2.33+ and one Zn2+ atom. In the second S2- site, S2- is bonded in a 1-coordinate geometry to three equivalent Mo+2.33+ and one Fe2+ atom. In the third S2- site, S2- is bonded in a 5-coordinate geometry to four Mo+2.33+ and one Fe2+ atom. In the fourth S2- site, S2- is bonded in a 5-coordinate geometry to four Mo+2.33+ and one Zn2+ atom.
36 MATERIALS SCIENCE↗
Materials Data on ZnFe(GeO3)2 by Materials Project
Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations
36 MATERIALS SCIENCE↗
Materials Data on ZnFe(SiO3)2 by Materials Project
Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations
36 MATERIALS SCIENCE↗
Materials Data on ZnFe(SO8)2 by Materials Project
FeZn(SO7)2O2 crystallizes in the monoclinic P2_1/c space group. The structure is one-dimensional and consists of four hydrogen peroxide molecules and two FeZn(SO7)2 ribbons oriented in the (1, 0, 0) direction. In each FeZn(SO7)2 ribbon, there are two inequivalent Fe sites. In the first Fe site, Fe is bonded to six O atoms to form FeO6 octahedra that share corners with two equivalent FeO6 octahedra and corners with two equivalent SO4 tetrahedra. The corner-sharing octahedral tilt angles are 38°. There are a spread of Fe–O bond distances ranging from 1.96–2.18 Å. In the second Fe site, Fe is bonded to six O atoms to form FeO6 octahedra that share corners with two equivalent FeO6 octahedra and corners with two equivalent SO4 tetrahedra. The corner-sharing octahedral tilt angles are 38°. There are a spread of Fe–O bond distances ranging from 1.82–2.19 Å. Zn is bonded in a 4-coordinate geometry to five O atoms. There are a spread of Zn–O bond distances ranging from 1.84–2.57 Å. There are two inequivalent S sites. In the first S site, S is bonded to four O atoms to form SO4 tetrahedra that share corners with two FeO6 octahedra. The corner-sharing octahedra tilt angles range from 45–53°. There is two shorter (1.48 Å) and two longer (1.50 Å) S–O bond length. In the second S site, S is bonded in a trigonal planar geometry to three O atoms. There are a spread of S–O bond distances ranging from 1.42–1.46 Å. There are fourteen inequivalent O sites. In the first O site, O is bonded in a single-bond geometry to one S atom. In the second O site, O is bonded in a single-bond geometry to one Fe atom. In the third O site, O is bonded in a distorted bent 150 degrees geometry to one Fe and one S atom. In the fourth O site, O is bonded in a single-bond geometry to one Zn atom. In the fifth O site, O is bonded in a distorted single-bond geometry to one O atom. The O–O bond length is 1.24 Å. In the sixth O site, O is bonded in a single-bond geometry to one S atom. In the seventh O site, O is bonded in a single-bond geometry to one Zn atom. In the eighth O site, O is bonded in a single-bond geometry to one Zn atom. In the ninth O site, O is bonded in a distorted bent 150 degrees geometry to one Fe and one S atom. In the tenth O site, O is bonded in a bent 150 degrees geometry to two Fe atoms. In the eleventh O site, O is bonded in a bent 120 degrees geometry to one Zn and one S atom. In the twelfth O site, O is bonded in a bent 120 degrees geometry to one Zn and one O atom. In the thirteenth O site, O is bonded in a bent 120 degrees geometry to one Fe and one S atom. In the fourteenth O site, O is bonded in a single-bond geometry to one S atom.
36 MATERIALS SCIENCE↗
Materials Data on ZnFe(SiO3)2 by Materials Project
Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations
36 MATERIALS SCIENCE↗
Materials Data on ZnFe(SO8)2 by Materials Project
FeZn(SO7)2O2 crystallizes in the monoclinic P2_1/c space group. The structure is one-dimensional and consists of four oxygen molecules and two FeZn(SO7)2 ribbons oriented in the (1, 0, 0) direction. In each FeZn(SO7)2 ribbon, there are two inequivalent Fe sites. In the first Fe site, Fe is bonded to six O atoms to form FeO6 octahedra that share corners with two equivalent FeO6 octahedra and corners with four SO4 tetrahedra. The corner-sharing octahedral tilt angles are 41°. There are a spread of Fe–O bond distances ranging from 2.01–2.07 Å. In the second Fe site, Fe is bonded to six O atoms to form FeO6 octahedra that share corners with two equivalent FeO6 octahedra and corners with two equivalent SO4 tetrahedra. The corner-sharing octahedral tilt angles are 41°. There are a spread of Fe–O bond distances ranging from 1.80–1.99 Å. Zn is bonded in a trigonal planar geometry to three O atoms. There are a spread of Zn–O bond distances ranging from 1.86–2.02 Å. There are two inequivalent S sites. In the first S site, S is bonded to four O atoms to form SO4 tetrahedra that share corners with two FeO6 octahedra. The corner-sharing octahedra tilt angles range from 47–57°. There are a spread of S–O bond distances ranging from 1.44–1.53 Å. In the second S site, S is bonded to four O atoms to form SO4 tetrahedra that share a cornercorner with one FeO6 octahedra. The corner-sharing octahedral tilt angles are 35°. There are a spread of S–O bond distances ranging from 1.47–1.51 Å. There are fourteen inequivalent O sites. In the first O site, O is bonded in a single-bond geometry to one S atom. In the second O site, O is bonded in a single-bond geometry to one Fe atom. In the third O site, O is bonded in a bent 150 degrees geometry to one Fe and one S atom. In the fourth O site, O is bonded in a distorted bent 120 degrees geometry to one Zn and one O atom. The O–O bond length is 1.37 Å. In the fifth O site, O is bonded in a single-bond geometry to one S atom. In the sixth O site, O is bonded in a single-bond geometry to one O atom. The O–O bond length is 1.25 Å. In the seventh O site, O is bonded in a single-bond geometry to one S atom. In the eighth O site, O is bonded in a distorted bent 120 degrees geometry to one Fe and one S atom. In the ninth O site, O is bonded in a bent 150 degrees geometry to two Fe atoms. In the tenth O site, O is bonded in a bent 150 degrees geometry to one Zn and one S atom. In the eleventh O site, O is bonded in a single-bond geometry to one Zn atom. In the twelfth O site, O is bonded in a bent 120 degrees geometry to one Fe and one S atom. In the thirteenth O site, O is bonded in a bent 120 degrees geometry to two O atoms. In the fourteenth O site, O is bonded in a single-bond geometry to one S atom.
36 MATERIALS SCIENCE↗
Controlling inversion disorder in a stoichiometric spinel magnet
In the study of frustrated quantum magnets, it is essential to be able to control the nature and degree of site disorder during the growth process, as many measurement techniques are incapable of distinguishing between site disorder and frustration-induced spin disorder. Pyrochlore-structured spinel oxides can serve as model systems of geometrically frustrated three-dimensional quantum magnets; however, the nature of the magnetism in one well-studied spinel, ZnFe 2 O 4 , remains unclear. Here, we demonstrate simultaneous control of both stoichiometry and inversion disorder in the growth of ZnFe 2 O 4 single crystals, directly yielding a revised understanding of both the collective spin behavior and lattice symmetry. Crystals grown in the stoichiometric limit with minimal site inversion disorder contravene all the previously suggested exotic spin phases in ZnFe 2 O 4 . Furthermore, the structure is confirmed on the F$\bar{4}$3m space group with broken inversion symmetry that induces antiferroelectricity. The effective tuning of magnetic behavior by site disorder in the presence of robust antiferroelectricity makes ZnFe 2 O 4 of special interest to multiferroic devices.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Three-dimensional checkerboard spin structure on a breathing pyrochlore lattice
The standard approach to realize a spin-liquid state is through magnetically frustrated states, relying on ingredients such as the lattice geometry, dimensionality, and magnetic interaction type of the spins. While Heisenberg spins on a pyrochlore lattice with only antiferromagnetic nearest-neighbor interactions are theoretically proven disordered, spins in real systems generally include longer-range interactions. The spatial correlations at longer distances typically stabilize a long-range order rather than enhancing a spin-liquid state. Both states can, however, be destroyed by short-range static correlations introduced by chemical disorder. Here, using disorder-free specimens with a clear long-range antiferromagnetic order, we refine the spin structure of the Heisenberg spinel ZnFe 2 O 4 through neutron magnetic diffraction. The unique wave vector (1, 0, $\frac{1}{2}$) leads to a spin structure that can be viewed as alternatively stacked ferromagnetic and antiferromagnetic tetrahedra in a three-dimensional checkerboard form. Stable coexistence of these opposing types of clusters is enabled by the bipartite breathing pyrochlore crystal structure, leading to a second-order phase transition at 10 K. The diffraction intensity of ZnFe 2 O 4 is an exact complement to the inelastic scattering intensity of several chromate spinel systems which are regarded as model classical spin liquids. Our results challenge this attribution, and suggest instead of the six-spin ring mode, spin excitations in chromate spinels are closely related to the (1, 0, $\frac{1}{2}$) type of spin order and the four-spin ferromagnetic cluster locally at one tetrahedron.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Zn speciation and fate in soils and sediments along the ground transportation route of Zn ore to a smelter
We discuss assessment of Zn toxicity/mobility based on its speciation and transformations in soils as critical for maintaining human and ecosystem health. Zn-concentrate (56% Zn as ZnS, sphalerite) has been imported through a seaport and transported to a Zn-smelter for several decades, and smelting processes resulted in aerial deposition of Zn and sulfuric acids in two geochemically distinct territories around the smelter (mountain-slope and riverside). XAFS analysis showed that the mountain-slope soils contained franklinite (ZnFe 2 O 4 ) and amorphous (e.g., sorbed) species of Zn(II), whereas the riverside sediments contained predominantly hydrozincite [Zn 5 (OH) 6 (CO 3 ) 2 ], sphalerite, and franklinite. The mountain-slope soils had low pH and moderate levels of total Zn (~1,514 ppm), whereas the riverside sediments had neutral pH and higher total Zn (12,363 ppm). The absence of sphalerite and the predominance of franklinite in the mountain-slope soils are attributed to the susceptibility of sphalerite and the resistance of franklinite to dissolution at acidic pH. These results are compared to previous Zn analyses along the transportation routes, which showed that Zn-concentrate spilled along the roadside in dust and soils underwent transformation to various O-coordinated Zn species. Overall, Zn-concentrate dispersed in soils and sediments during transportation and smelting transforms into Zn phases of diverse stability and bioavailability during long-term weathering.
36 MATERIALS SCIENCE↗
Chapter 8: Time-Resolved Photoluminescence Characterization of Polycrystalline Thin-Film Solar Cells
This chapter describes some photoluminescence (PL) approaches to characterize thin film solar cells with emphasis on time-resolved methods. Spectral PL analysis is complementary and was recently reviewed. Since TRPL is not very commonly used in PV characterization, we consider interface and bulk recombination in the test structures and in devices, briefly describe charge-carrier transport and recombination microscopy, and finally, summarize and compare some CdTe, CdSeTe, CIGS, kesterite, and perovskite EO characteristics.
bulk recombination↗