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Highlights: [•] Title ferrites were prepared by hydrothermal techniques (sub and supercritical). [•] In supercritical (SCW) conditions highly monodispersive samples were obtained. [•] All samples are semiconductors; n-type or p-type response depends on the composition. [•] Superparamagnetic and relaxor ferroelectric response coexist in SCW samples. [Copyright &y& Elsevier]

Highlights: [•] The Li x Mn3− x − y Fe y O4 spinels show a versatile electronic behavior. [•] Optimal compositional ranges for different application fields are proposed. [•] Frustrated ferromagnetic response is compositionally driven. [•] High ε′ values are obtained when B sites are occupied by both Mn and Fe cations. [•] High lithium contents are linked to the electrochemical behavior. [ABSTRACT FROM AUTHOR]

Abstract: We have fabricated SrLaMnTiO6 thin films by PLD on different substrates (SrTiO3, LaAlO3 and Si). Their texture, width, homogeneity and morphology have been evaluated from XRD, SEM and complex impedance spectroscopy. The thickness ranged between 500 and 8800nm depending on the synthesis conditions. The epitaxial growing could be interpreted in terms of two contributions of microstructural origin: a matrix part and some surface formations (hemi-spheres), with different texture and size distributions. The films were nanostructured and contained vertically aligned nanopores (VANPs) with a pore average size of 30–60nm, which are very interesting for eventual SOFC anode applications. Magnetization results indicate an improved response respect to nano-sized powder samples. [ABSTRACT FROM AUTHOR]

Abstract: New spinel-type phases of general formula LiMMnO4 (M=Cr, Ti), derived from LiMn2O4 by substitution of Mn3+ by Cr3+ or Mn4+ by Ti4+, have been obtained and characterised. Neutron diffraction refinements confirm that both phases crystallise in the space group, giving the cation distributions [Li]8a [CrMn]16d O4 and [Li0.66Ti0.34]8a [Li0.34MnTi0.66]16d O4. Electrical conductivity has been examined by various techniques showing that these materials behave as semiconductors. The electrochemical behaviour indicates different oxidation–reduction steps in both cases concomitant with the insertion/deinsertion of lithium in non-reversible processes. X-ray diffraction patterns show that the above process is topotactic in LiCrMnO4. Magnetic data and neutron diffraction measurements show that no long-range magnetic ordering is present, suggesting a spin-glass transition for M=Cr at low temperature, while for M=Ti the presence of non-magnetic ions in the octahedral sublattice provokes an inherent magnetic frustration. [Copyright &y& Elsevier]

Production of volatile aroma compounds, and quality parameters, were monitored in relation to the activity of lipoxygenase, pyruvate decarboxylase, alcohol dehydrogenase and alcohol o-acyltransferase during maturation of ‘Fuji’ apples. Acetate esters increased during maturation and were quantitatively the most significant compounds contributing to ‘Fuji’ aroma. Increase in acetate ester production was associated with the availability of the necessary alcohol precursors. Principal component analysis revealed a clear separation according to sampling date, which accounted for up to 67% of total variance, and allowed ‘Fuji’ apples used in this study to be classified into three ripeness stages. Overall the results suggest that precursor availability for the related enzymes is a more significant factor than enzyme activity for the development of aroma during on-tree maturation of ‘Fuji’ apples. [Copyright &y& Elsevier]

Abstract: Manganites are materials that show remarkable phenomena related to charge orbital ordering (CO/OO) and it is extremely important to understand the fundamental nature of this behaviour. This paper reports on the structural, electronic and magnetic behaviour of the new SrBiMn1.75Ti0.25O6 manganite and the dependence of these properties with temperature. A detailed structural analysis has been carried out by electron, X-ray, neutron diffraction between 4 and 700K. The electron diffraction patterns obtained at room temperature (RT) evidence that the average structure ( and c ∼2a p ) presents a modulation that doubles the a and c lattice parameters. A very high charge ordering (CO) transition temperature of 510K, similar to that found for the non-doped material, SrBiMn2O6, is observed. Above this temperature the symmetry changes from orthorhombic to tetragonal. The conductivity and susceptibility data show a strong interdependence with the structural transition. The activation energy decreases from 0.24eV to 0.12eV below and above 510K, respectively. On the other hand, the high value of the magnetic moment (μ eff =9.34 μ B), observed between 300 and 500K, is interpreted in terms of the existence of Mn4 magnetic clusters. Finally, extra maxima appearing in neutron diffraction patterns at lower temperatures are interpreted considering the stabilization of AFM interactions, consistent with an A-type magnetic ordering. The results are discussed in the framework of charge ordering/orbital ordering and cluster models. [Copyright &y& Elsevier]

Abstract: Microcrystalline powders of Sr1−x □ x LaMnTiO6−δ (0≤ x ≤0.15) perovskites have been synthesized by the sol–gel method. Structural characterization from neutron diffraction data shows tetragonal symmetry for all samples in the whole temperature range explored (5–700K) and HRTEM analysis confirms it at the micro scale. Structural refinements suggest that Sr/La and Mn/Ti cations are placed at random in A and B sublattices, respectively, being the vacancies exclusively located on the former sites. Doping with vacancies in the A sites does not provoke any extra structural ordering or distortion but modifies the electronic scenario at the B-sites, leading to an enhancement of Griffiths phase as the amount of vacancies, x, increases. Semiconductor behaviour has been observed, without any transition to metallic state, with typical activation energies of 0.15eV. The intrinsic magnetic frustrated behaviour is described in terms of a cluster-glass model. [Copyright &y& Elsevier]

Abstract: We report on the room temperature strong (∼80%) electroresistance (ER) in the double perovskite with mixed Mn valence: Sr2−x Gd x MnTiO6, 0≤ x ≤1. Both, continuous and pulsed current–voltage curves are almost identical which indicates that the observed electroresistance is not associated with heating. This is also supported by simultaneous temperature measurements. ER is negligible (absent) in the x =0 compound and increases with the increase of Gd content ‘x’. The amplitude of ER has a maximum for x =0.75, suggesting that ER is determined by both the double exchange and the Mn3+ concentration. At the same time, magnetic interactions change from the antiferromagnetic (x =0) to ferromagnetic ones as x →1, thus linking the ER with ferromagnetism. [Copyright &y& Elsevier]

Standard quality parameters, consumer acceptability, emission of volatile compounds and ethylene production of ‘Mondial Gala®’ apples (Malus × domestica Borkh.) were determined in relation to storage atmosphere, storage period and shelf-life period. Fruit were harvested at the commercial date and stored in AIR (21kPa O2:0.03kPa CO2) or under three different controlled atmospheres (CAs): LO (2kPa O2:2kPa CO2), ULO1 (1kPa O2:1kPa CO2), or ULO2 (1kPa O2:2kPa CO2). Fruit samples were analysed after 12 and 26 weeks of storage plus 1 or 7d at 20°C. Apples stored in CA maintained better standard quality parameters than AIR-stored fruit. The volatile compounds that contributed most to the characteristic aroma of ‘Mondial Gala®’ apples after storage were butyl, hexyl and 2-methylbutyl acetate, hexyl propanoate, ethyl butanoate, ethyl hexanoate, ethyl, butyl and hexyl 2-methylbutanoate. Data obtained from fruit analysis were subjected to principal component analysis (PCA). The apples most accepted by consumers showed the highest emission of ethyl 2-methylbutanoate, ethyl hexanoate, tert-butyl propanoate and ethyl acetate, in addition to the highest titratable acidity and firmness values. [Copyright &y& Elsevier]

The production of aroma volatile compounds and standard quality attributes, in addition to lipoxygenase (LOX), hydroperoxide lyase (HPL), pyruvate decarboxylase (PDC), alcohol dehydrogenase (ADH) and alcohol o-acyltransferase (AAT) activities, were assessed during maturation of ‘Pink Lady®’ apples. Low production of aroma volatiles was observed in early harvested fruit, which gradually increased as ripeness approached. Hexyl acetate, hexyl 2-methylbutanoate, hexyl hexanoate, hexyl butanoate, 2-methylbutyl acetate and butyl acetate were prominent within the blend of volatiles produced by fruit throughout maturation. Multivariate analysis showed these compounds had the highest influence on differentiation of maturity stages, indicating that aroma volatile emission is an important factor for definition of fruit ripeness, which suggests production of these esters might be useful as an index of maturity. No large variations in AAT activity were found throughout the experimental period despite increasing ester emission, suggesting the enhancement of ester production by ‘Pink Lady®’ apples at ripening arises mainly from greater availability of substrates. Increased LOX activity was observed at later stages of fruit development, and the possible role of this enzyme activity on enhanced capacity for aroma volatile biosynthesis in more mature fruit is discussed. [Copyright &y& Elsevier]

‘Fuji’ apples were harvested at two different dates, over two consecutive years (1999 and 2000), and stored under different atmosphere conditions: AIR (21 kPa O2+0.03 kPa CO2), SCA (3 kPa O2+2 kPa CO2) or ULO (1 kPa O2+2 kPa CO2). After 3, 5 or 7 months of storage plus 1 or 10 days of ripening at 20 °C, aroma volatile emission and quality parameters were measured. Generally, the highest total aroma emission was obtained after 5-months storage and 1 day of ripening at 20 °C regardless of atmosphere conditions, for early-harvested fruit. After 7-months storage, the ULO atmosphere depressed total aroma volatile emission. The compounds contributing mostly to the characteristic aroma of ‘Fuji’ apples were ethyl 2-methylbutanoate, 2-methylbutyl acetate and hexyl acetate, and their concentrations were higher the first day after removal from storage at 5, 3 and 7 months, respectively. Storage conditions and season had a significant effect on aroma volatile compounds. [Copyright &y& Elsevier]