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Investigation of the Nd 2− ε Ba 3+ ε (Fe,Co) 5 O 15− δ system, combining X-ray diffraction and electron microscopy, has allowed a tetragonal quintuple ordered perovskite “ a p × a p × 5a p ” phasoid inter-grown within a single cubic perovskite matrix to be evidenced for ε =0. This nanoscale chemically twinned perovskite is compared with other members, Ln=Sm, Eu, Pr. The unusual long range ordering of the layers develops strains due to size mismatch between Ba 2+ and Ln 3+ cations. Importantly, two factors allow the strains to be decreased: (i) special intergrowths of double (LnBaFe 2 O 6− δ ) and triple (LnBa 2 Fe 3 O 9− δ ) perovskite ribbons/layers oriented at 90°, (ii) nanoscale chemical twinning. The spin locking effect of the nano-domain boundaries upon the magnetic properties of these perovskites is discussed. [ABSTRACT FROM AUTHOR]

Handedness is an essential attribute of chiral nanocrystals, having a major influence on their properties. During chemical growth, the handedness of nanocrystals is usually tuned by selecting the corresponding enantiomer of chiral molecules involved in asymmetric growth, often known as chiral inducers. We report that, even using the same chiral inducer enantiomer, the handedness of chiral gold nanocrystals can be reversed by using Au nanorod seeds with either single crystalline or pentatwinned structure. This effect holds for chiral growth induced both by amino acids and by chiral micelles. Although it was challenging to discern the morphological handedness for L‐cystine‐directed particles, even using electron tomography, both cases showed circular dichroism bands of opposite sign, with nearly mirrored chiroptical signatures for chiral micelle‐directed growth, along with quasi‐helical wrinkles of inverted handedness. These results expand the chiral growth toolbox with an effect that might be exploited to yield a host of interesting morphologies with tunable optical properties. [ABSTRACT FROM AUTHOR]

Handedness is an essential attribute of chiral nanocrystals, having a major influence on their properties. During chemical growth, the handedness of nanocrystals is usually tuned by selecting the corresponding enantiomer of chiral molecules involved in asymmetric growth, often known as chiral inducers. We report that, even using the same chiral inducer enantiomer, the handedness of chiral gold nanocrystals can be reversed by using Au nanorod seeds with either single crystalline or pentatwinned structure. This effect holds for chiral growth induced both by amino acids and by chiral micelles. Although it was challenging to discern the morphological handedness for L‐cystine‐directed particles, even using electron tomography, both cases showed circular dichroism bands of opposite sign, with nearly mirrored chiroptical signatures for chiral micelle‐directed growth, along with quasi‐helical wrinkles of inverted handedness. These results expand the chiral growth toolbox with an effect that might be exploited to yield a host of interesting morphologies with tunable optical properties. [ABSTRACT FROM AUTHOR]

Phase equilibria in the 1/2Y2O3–SrO–1/2Fe2O3 system were systematically studied at 1373 K in air. The homogeneity ranges and crystal structure of the solid solutions Sr1−xYxFeO3−δ with 0.875 ≤ x ≤ 1 (sp. gr. Pnma) and 0.05 ≤ x ≤ 0.25 (sp. gr. Pm3 m) and Sr3−zYzFe2O7−δ with 0 ≤ z ≤ 0.25 (sp. gr. I4/mmm) were determined by X‐ray diffraction analysis of quenched samples. The structural parameters of the single‐phase oxides were refined by the Rietveld profile method. The isothermal‐isobaric phase diagram for the 1/2Y2O3–SrO–1/2Fe2O3 system at 1373 K in air is presented. The changes of oxygen content in the solid solutions Sr1−xYxFeO3−δ (0.05 ≤ x ≤ 0.25) and Sr3−zYzFe2O7−δ with 0 ≤ z ≤ 0.25 vs temperature in air were determined by the thermogravimetric analysis. Oxygen content was also calculated from the iodometric titration results. The gradual substitution of strontium by yttrium in Sr1−xYxFeO3−δ (0.05 ≤ x ≤ 0.25) leads to a decrease in the oxygen content and the mean oxidation state of iron. The average thermal expansion coefficients for Sr1−xYxFeO3−δ (0.875 ≤ x ≤ 1 and 0.05 ≤ x ≤ 0.25) and Sr3−zYzFe2O7−δ (0 ≤ z ≤ 0.25) were calculated within the temperature range 298‐1373 K in air. The phase diagram of the 1/2Y2O3 ‐ SrO ‐ 1/2Fe2O3 system (T=1373 K, Po2=0.21 atm). [ABSTRACT FROM AUTHOR]