Structures of LuFeO3(ZnO)m (m =1, 4, 5 and 6)

Novel SnO2(ZnO:Sn)m superlattice nanoparticles for ultra-low ppb-level H2S detection

Novel zero-dimensional SnO2(ZnO:Sn)m superlattice nanoparticles were synthesized by a simple method of annealing ZnO nanoparticles precoated with the sol-gel Sn-Zn-O precursor. The annealing temperature and duration are systematically evaluated, and...

Recent progress of the single crystal growth of homologous (InGaO3)m(ZnO)n

Crystal structure of the homologues series of (InGaZnO3)m(ZnO)n.

Single crystal growth of bulk InGaZnO4 and analysis of its intrinsic transport properties

Large, high-quality InGaZnO₄ single crystals grown by high-pressure optical floating zone method and its electrical and optical properties.

Photocatalytic H2 evolution from water-methanol system by anisotropic InFeO3(ZnO)(m) oxides without cocatalyst in visible light

InFeO3(ZnO)m series of oxides are found to give unprecedented H2 evolution from water-methanol mixtures without using any cocatalysts. This family of compounds has an anisotropically layered structure in which Zn/FeOn polyhedra are sandwiched between InO6 octahedral layers. Local structure characterization by X-ray absorption spectroscopy reveals that Zn coordination changes from pentacoordinated to tetrahedral geometry across the series, whereas Fe geometry remains trigonal bipyramidal in all the compounds. This peculiar structure is conducive for a spatial separation of photogenerated charges reducing recombination losses. Band gap energies calculated from absorption spectra indicate potential visible light activity, and this may be due to the orbital mixing of Fe 3d and O 2p as revealed by pre-edge features of X-ray absorption spectra. Band positions are also advantageously placed for a visible light H2 generation and is indeed found to be the case in methanol-assisted water splitting with standardized hydrogen evolution of ∼19.5 mmol g(-1) h(-1) for all the catalysts.

Investigations into variations in local cationic environment in layered oxide series InGaO3(ZnO)m (m = 1-4)

Layered oxides of the series InGaO3(ZnO)m (m = 1-4) are interesting due to their structural anisotropy. Here, we report a comprehensive study of their structural details, focusing on the local cationic environment in bulk powder samples by MASNMR and EXAFS, which is hitherto not attempted. It is found that the Ga geometry varies gradually from pure pentacoordinated to a mixture of penta and tetracoordinated with increasing amounts of tetracoordination as we move across the series, contrary to previous reports suggesting exclusively trigonal bipyramidal coordination in all the compounds. A similar observation is also made in the case of Zn and structural evolution involving the dissolution of Ga in a ZnO4 tetrahedral network in a sandwich layer can be discerned, as the insulating ZnO layer size increases.

Structure of (Ga2O3)2(ZnO)13 and a unified description of the homologous series (Ga2O3)2(ZnO)(2n + 1)

The structure of (Ga(2)O(3))(2)(ZnO)(13) has been determined by a single-crystal X-ray diffraction technique. In the monoclinic structure of the space group C2/m with cell parameters a = 19.66 (4), b = 3.2487 (5), c = 27.31 (2) Å, and β = 105.9 (1)°, a unit cell is constructed by combining the halves of the unit cell of Ga(2)O(3)(ZnO)(6) and Ga(2)O(3)(ZnO)(7) in the homologous series Ga(2)O(3)(ZnO)(m). The homologous series (Ga(2)O(3))(2)(ZnO)(2n + 1) is derived and a unified description for structures in the series is presented using the (3+1)-dimensional superspace formalism. The phases are treated as compositely modulated structures consisting of two subsystems. One is constructed by metal ions and another is by O ions. In the (3 + 1)-dimensional model, displacive modulations of ions are described by the asymmetric zigzag function with large amplitudes, which was replaced by a combination of the sawtooth function in refinements. Similarities and differences between the two homologous series (Ga(2)O(3))(2)(ZnO)(2n + 1) and Ga(2)O(3)(ZnO)(m) are clarified in (3 + 1)-dimensional superspace. The validity of the (3 + 1)-dimensional model is confirmed by the refinements of (Ga(2)O(3))(2)(ZnO)(13), while a few complex phenomena in the real structure are taken into account by modifying the model.

Multi-component transparent conducting oxides: progress in materials modelling

Transparent conducting oxides (TCOs) play an essential role in modern optoelectronic devices through their combination of electrical conductivity and optical transparency. We review recent progress in our understanding of multi-component TCOs formed from solid solutions of ZnO, In(2)O(3), Ga(2)O(3) and Al(2)O(3), with a particular emphasis on the contributions of materials modelling, primarily based on density functional theory. In particular, we highlight three major results from our work: (i) the fundamental principles governing the crystal structures of multi-component oxide structures including (In(2)O(3))(ZnO)(n) and (In(2)O(3))(m)(Ga(2)O(3))(l)(ZnO)(n); (ii) the relationship between elemental composition and optical and electrical behaviour, including valence band alignments; (iii) the high performance of amorphous oxide semiconductors. On the basis of these advances, the challenge of the rational design of novel electroceramic materials is discussed.

High-resolution electron microscopy of a modulated structure in InMO3(ZnO) m (M = In, Fe, Ga, and Al; m = integer): effect of solid solution formation

The structure of InMO3(ZnO) m (M = In, Fe, Ga, and Al; m = integer) is built from InO2 1− (In–O) and MZn m ,O m+1 1m (M/Zn–O) layers stacked alternately. A modulated structure of these compounds results from the ordering of M ions in the M/Zn–O layers. The modulated structures of InMO3(ZnO)13 (M = In0.5A0.5; A = Fe, Ga, and Al), a solid solution of InInO3(ZnO)13 and InMO3(ZnO)13 (M =Fe, Ga, and Al), have been studied by high-resolution electron microscopy. The main and satellite spots of the electron diffraction patterns are indexed as ha* + kb* + lc* + mq by using the four dimensional superspace group approach. Based on the crystal system of the basic structure and the modulation wave vector q, the electron diffraction patterns are classified according to three categories with typical parameters: (1) monoclinic unit cell of a = 0.57 nm, b = 0.33 nm, c = 4.0 nm, β = 93° and q = b*/18.1; (2) monoclinic unit cell of a = 0.57 nm, b = 0.33 nm, c = 4.0 nm, β = 93°, and q = b*/22.5 + c*/2; (3) triclinic unit cell of a = 0.57 nm, b = 0.33 nm, c = 4.0 nm, α = 95°, β = 95°, γ = 30°, and q = a*/12.1 + b*/18.1 + c*/32.3. Among these, the first is the same as that of their constituent compounds In2O3(ZnO)13 and InMO3(ZnO)13 (M = Fe, and Ga), while the second and the third are different. In high-resolution image, the modulated structure appears as zig-zag contrast within the M/Zn–O layers. The periodicity of this zig-zag contrast along the M/Zn–O layer in InMO3(ZnO)13 (M = In0.5A0.5; A = Fe, Ga, and Al) is between those of InInO3(ZnO)13 and InMO3(ZnO)13 (M = Fe, Ga, and Al).

Superspace description of the homologous series Ga2O3(ZnO)m

A unified description for the structures of the homologous series Ga2O3(ZnO)m, gallium zinc oxide, is presented using the superspace formalism. The structures were treated as a compositely modulated structure consisting of two subsystems. One is constructed with metal ions and the other with O ions. The ideal model is given, in which the displacive modulations of ions are well described by the zigzag function with large amplitudes. Alternative settings are also proposed which are analogous to the so-called modular structures. The validity of the model has been confirmed by refinements for phases withm= 6 andm= 9 in the homologous series. A few complex phenomena in real structures are taken into account by modifying the ideal model.

Rules of structure formation for the homologous InMO3(ZnO)n compounds

The formation mechanisms that lead to the layered M-modulated InMO3(ZnO){n} structures (M=In, Ga, and Al; n=integer) are revealed and confirmed by first-principles calculations based on density functional theory. We show that all ground state structures of InMO3(ZnO){n} satisfy the octahedron rule for the InO2 layers; they contain an inversion domain boundary located at the M and Zn fivefold trigonal bipyramid sites and maximize the hexagonality in the (MZn{n})O{n+1} layers. They also obey the electronic octet rule. This understanding provides a solid basis for studying and understanding the physical properties of this group of homologous materials.

Relation between In ion ordering and crystal structure variation in homologous compounds InMO3(ZnO)m (M = Al and In; m = integer)

The relation between the ordering of In ions and the structure variation of homologous compounds InInO3(ZnO)13 and InAlO3(ZnO)m (m = 4, 5, and 13) have been studied by high-resolution transmission electron microscopy. It is revealed that InMO3(ZnO)m is a layered structure, consisting of InO2(1-) (In-O) and MZn(m)Om+1(1+) (M/Zn-O) layers stacked alternatively. Structure variations from the basic one, caused by the ordering of In ions in the M/Zn-O layers, are observed both in In2O3(ZnO)m and InAlO3(ZnO)m. In In2O3(ZnO)m, a modulated structure appearing as zig-zag shaped contrast in the high-resolution image was found and is considered to be caused by the ordering of In ions along the zig-zag contrast area. In InAlO3(ZnO)m, no modulated structure was found. Instead, planar defect structures appearing in Al/Zn-O layers were observed. It is shown that this defect structure is caused by the excess introduction of In ions into the Al/Zn-O layers and the ordering of these In ions. By comparing the results of InInO3(ZnO)m and InAlO3(ZnO)m, it is shown that the reasons for the In ion ordering is the discrepancy between the larger In ion size and the smaller oxygen void for M/Zn ions in M/Zn-O layers.