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Single and multilayer films of La0.67Sr0.33MnO3 and CoFe2O4 were deposited by spin-coating. The all-alkoxide precursors allowed inorganic gel films of extreme homogeneity to be formed and converted to phase pure complex oxides at low temperatures. La0.67Sr0.33MnO3 films were made with La- and Ca-methoxy-ethoxides and Mn19O12(moe)14(moeH)10 as precursors at 800 °C. The CoFe2O4 films were obtained at extremely low 275 °C, using a new CoFe2-methoxyethoxide precursor. The decomposition and microstructural development on heating was described by TG, TEM, XRD and IR spectroscopy. XRD showed no spurious phases and the unit-cell dimensions coincided quite well with literature values of the targeted phases. The structural, magnetic and electronic properties of these films established their phase purity and high quality with physical properties comparable to films deposited by physical deposition methods. The magnetic and magneto transport results are presented for single, bi- and tri- layer structures. The magnetically soft La0.67Sr0.33MnO3 layer was exchange coupled to the magnetically hard CoFe2O4 layer, giving rise to interesting switching behaviour in magnetism and magneto-transport properties. © 2021 The Authors. European Journal of Inorganic Chemistry published by Wiley-VCH GmbH

A carbothermal nitridation route to nanophase ZrN1-xCx powder using nitrogen gas and a highly homogeneous solution derived carbon-ZrO2 nanocomposite is described. Composites with 2-4 nm sized ZrO2 ...

Carbothermal reduction of Zr-sucrose gels powders into nano-phase ZrC, or ZrC-Zr(C,O) core-shell powders, via a composite of 2–4 nm sized ZrO2 and amorphous carbon, is described. Samples with 1.7–20 sucrose-carbon:Zr ratio gels heated to 1495 °C at 10 °Cmin−1, with 3 and 30 min hold time were studied in detail using; TG, XRD, SEM, TEM, STEM-EDX, and XPS with Ar+-ion etching. After 1495 °C, 3 min, the samples with 12-20C:Zr ratios yielded weakly agglomerated 30 to 40 nm sized ZrC particles, surrounded by a dense 5 nm thick shell of Zr(C,O). With 5C:Zr significant amounts of ZrO2 was present after heating at 1495 °C for 3 min, while after 30 min annealing, ZrC particles without residual amorphous carbon was obtained. Minor amounts of zirconia was found in most samples, which in similarity with the 5 nm Zr(C,O) shell, is believed to stem from post synthesis oxidation.

A low-cost template-free solution chemical route to highly porous nanocrystalline sponges of ZnO-EuO1.5 with 0-5 mol % Eu is presented. The process uses Zn- and Eu-acetate-nitrate and triethanolamine as precursors in methanol. After evaporation of the solvent and heating at 200 °C for 3 min, crystalline ZnO:Eu sponges with minor amounts of organic residues were obtained. Heating to 400 °C replaced the organics with carbonate, which in its turn was decomposed at temperatures below 600 °C, forming ZnO:Eu sponges. Samples heated to 200-1000 °C for 3 min were studied with XRD, SEM, TEM, TG, XPS, and IR spectroscopy. The ZnO:Eu crystallite sizes could be tuned from below 10 nm for sponges prepared at 200-500 °C, to over 100 nm range at 900 °C, without sintering of the overall microstructure. XRD showed the presence of hexagonal ZnO:Eu (or at 700-1000 °C, ZnO:Eu and cubic Eu2O3) as the only phases present. The ZnO:Eu had slightly larger unit cell dimensions than the literature value of ZnO for samples obtained at 200-600 °C, while the unit cells of samples obtained at higher temperatures were quite close to the value of undoped ZnO. XPS showed that Eu was mainly in its 3+ state and well-distributed within the sponges but segregated at the ZnO sponge surface upon heating at 700-1000 °C, in accordance with XRD studies showing Eu2O3 formation.

The detailed structure of ZnO doped with 5 at.% (metal) of the large aliovalent Eu3+-ions was investigated using EXAFS to describe the local Eu and Zn coordination. The microstructure, crystalline phases, contents and ZnO unit-cell parameters for the ZnO:5%Eu sponges synthesised at 200 to 900 oC were obtained by XRD, SEM, and TEM analysis. XRD showed peaks solely of h-ZnO for the 600 oC sample, while heating at 700 oC and higher caused phase separation into h-ZnO:Eu and c-Eu2O3. XRD showed a close to zero increase in ZnO unit cell-volume of ca. 0.4 vol%, compared to un-doped ZnO for the non-phase separated, clean oxide made at 600 oC. The Zn EXAFS data showed an almost intact local ZnO structure. The Eu EXAFS showed an unusually low coordination number (CN) of ca. 5 for the 200-600 oC samples, while the CN increased for higher temperatures, in concert with the formation of c-Eu2O3. 23 DFT-generated theoretical ZnO structures containing Eu-clusters built from 1 to 4 Eu3+-Zn2+-vacancy- Eu3+ pairs were compared with the experimental data. The lowest formation energies and ZnO unit-cell volume increase versus un-doped ZnO (0.6-0.7 vol%), were obtained when combining two or four Eu3+-Zn2+-vacancy- Eu3+ pairs into Eu4 and Eu8 clusters showing an average Eu CN of ca. 5. These theoretically determined lowest energy structures were all in good agreement with the experimental results obtained by EXAFS and XRD. Photoluminescence excitation and emission spectra performed on the ZnO:5at%Eu sponges obtained at various temperatures, showed strong quenching of the characteristic Eu3+ transitions for samples obtained at 600 and 800 °C, most likely due to changes in the ZnO defect states, which are crucial for Eu3+ excitation, and due to self-quenching upon Eu clustering and c- Eu2O3 phase separation. Thus, the optical data further supported Eu clustering found by EXAFS, DFT and XRD techniques, corroborating structure-property relationships in these materials. Overall, as far as we can find, the findings reported herein point to a doping structure very different from those previously proposed in the literature. It demonstrates that the semiconductor ZnO can host molecular-sized clusters of metal-oxides, very dissimilar to ZnO.

Nanocrystalline ZnO sponges doped with 5 mol% EuO1.5 are obtained by heating metal–salt complex based precursor pastes at 200–900 °C for 3 min. X-ray diffraction, transmission electron microscopy, and extended X-ray absorption fine structure (EXAFS) show that phase separation into ZnO:Eu and c-Eu2O3 takes place upon heating at 700 °C or higher. The unit cell of the clean oxide made at 600 °C shows only ≈0.4% volume increase versus undoped ZnO, and EXAFS shows a ZnO local structure that is little affected by the Eu-doping and an average Eu3+ ion coordination number of ≈5.2. Comparisons of 23 density functional theory-generated structures having differently sized Eu-oxide clusters embedded in ZnO identify three structures with four or eight Eu atoms as the most energetically favorable. These clusters exhibit the smallest volume increase compared to undoped ZnO and Eu coordination numbers of 5.2–5.5, all in excellent agreement with experimental data. ZnO defect states are crucial for efficient Eu3+ excitation, while c-Eu2O3 phase separation results in loss of the characteristic Eu3+ photoluminescence. The formation of molecule-like Eu-oxide clusters, entrapped in ZnO, proposed here, may help in understanding the nature of the unexpected high doping levels of lanthanide ions in ZnO that occur virtually without significant change in ZnO unit cell dimensions.

The optical features and photocatalytic activity of porous undoped and Eu3+-doped zinc oxide (ZnO) sponge-like structures, annealed at various temperatures, were assessed to establish the relations ...

Herein, a catalytic reductive fractionation of lignocellulose is presented using a heterogeneous cobalt catalyst and formic acid or formate as a hydrogen donor. The catalytic reductive fractionation of untreated birch wood yields monophenolic compounds in up to 34 wt % yield of total lignin, which corresponds to 76 % of the theoretical maximum yield. Model compound studies revealed that the main role of the cobalt catalyst is to stabilize the reactive intermediates formed during the organosolv pulping by transfer hydrogenation and hydrogenolysis reactions. Additionally, the cobalt catalyst is responsible for depolymerization reactions of lignin fragments through transfer hydrogenolysis reactions, which target the β-O-4' bond. The catalyst could be recycled three times with only negligible decrease in efficiency, showing the robustness of the system.

An efficient, template-free solution-chemical route to nanostructured ZnO sponges is presented: A mixture of Zn(NO3)2·6H2O, Zn(OAc)2·2H2O, and triethanolamine in methanol was evaporated to a highly viscous liquid and rapidly heated to >200 °C for 1–3 min to achieve highly porous, nanocrystalline sponges of ZnO. The viscous precursor concentrate obtained on evaporation in air was characterized by TG, DSC, and IR spectroscopy, and the product ZnO sponges by XRD, SEM, TEM, and IR spectroscopy. The fast reaction forming ZnO started at 140 °C and finished within a few seconds. Scherrer analysis of the XRD peak broadening showed average crystallite sizes of 8 to 11 nm for ZnO prepared by annealing at 200–450 °C (3 min), while grain growth to 134 nm was observed from 500 to 900 °C (3 min). The ZnO powders obtained at 200–900 °C had cell dimensions of a = 3.25 A and b = 5.21 A, matching the ZnO literature data well. SEM and TEM analyses showed highly porous, bread-like 3D nanostructures built by ca. 30–70 nm thic...

The sintering of a 14 ​wt% nickel nano-dot coated NbC powder was investigated using dilatometry in combination with XRD, ToF-ERDA, PIXE, SEM-EDS/EBSD/TKD, and TEM-HAADF/EDS/EELS for analysis of samples heated to 1375, 1405 and 1500 ​°C, with a 30 ​min annealing. The main sintering step at 1110–1375 ​°C, was succeeded by a slower step, centred at 1405 ​°C, before the final smaller densification step to 1500 ​°C. NbC grain-growth took place on heating at 1500 ​°C for 30 ​min; from ca. 0.5–5 ​μm (average 1 ​μm) at 1375 and 1405 ​°C to ca. 5–30 ​μm (average 10 ​μm) 1500 ​°C for 30 ​min. The NbC0.91-0.94 phase showed a micro-hardness of 1700–2300 HV0.05. The binder phase consisted of the unprecedented textured c-Nb0.15Ni0.85 and h-Nb0.2Ni0.8 phases. The Nb–Ni binder phase yielded micro-hardness values of 1150–1250 (1375–1405 ​°C) to 810 HV0.05 (1500 ​°C, 30 ​min), which greatly exceeds nickel and is higher than Fe3Al.

A fast, low cost solution route to nickel dot coated NbC powder using Ni(NO3)26H2O, Ni(OAc)24H2O and triethanolamine (TEA) as precursors in methanol solvent was developed. After mixing the precursor solution with 50–300 ​nm sized NbC powder and evaporation of the solvent, heating to 150 ​°C, or higher, yielded NbC powder evenly covered with well-dispersed nickel metal dots, 6–25 ​nm in size, depending on the nickel loading and temperature. Coatings yielding 4 to 14 ​wt% nickel loading were studied at temperatures from 200 to 700 ​°C, using TG-DTA, XRD, SEM, XPS with Ar+-ion etching, TEM/DF, and STEM/HAADF/EDS.