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Highly sodium deficient Na 0.6 NbO 3 (NN) ceramics were prepared and characterized. Their mean structure could be described by a mixture of the predominant P polymorph (S.G. Pbma) and the Q phase (S.G. P 2 1 ma), at room temperature, as deduced from Rietveld refinements of Powder X-ray diffraction and Raman scattering data. Besides, microstructural and compositional heterogeneity was evidenced from HRTEM and XPS analyses. Dielectric measurements on this highly vacancies-containing NN material indicated a hysteretic transition taking place at ~12 and −18 °C on the heating and cooling regimes, respectively. This means a considerable shift to lower temperatures of the transition temperatures concerning the P/Q transformations previously described for the NaNbO 3 material. At an intermediate frequency of 10 kHz, maximum permittivity and tangent loss values of ε' = 1250 and tgδ = 2 were obtained on heating, whereas lower values of ε' = 65 and tgδ = 0.04 were displayed on cooling regime. These anomalies were interpreted in terms of ferrolectric-antiferroelectric-paralectric phase-transitions implying a PTCR behavior within certain temperature range. This response, observed in this complex material for the first time, has interesting implications for the possible application of NN ceramics in sensing and dielectric materials fields. [ABSTRACT FROM AUTHOR]

Abstract: Pre-storage at 20°C before cold storage was used to improve volatile compound emissions of ‘Big Top’ nectarine and ‘Early Rich’ peach fruit without negatively affecting quality measures and sensory attributes. Commercially harvested fruit were subjected to pre-storage at 20°C for 0, 10, 24, or 36h and then stored at −0.5°C for 10, 20, or 40 d. After cold storage, the fruit were kept at 20°C for up to three days. ‘Big Top’ nectarines given 10h pre-storage followed by 10 and 20 d cold storage were perceived as more flavourful, juicy, and sweet, had higher soluble solid contents, and contained more butyl propanoate, 2-methybutyl-2-methylpropanoate, and 2-methyl-1-butanol than control fruit. ‘Early Rich’ peaches given 36h pre-storage followed by 20 d cold storage were perceived as sweeter and had more propyl acetate, pentyl acetate, and 2-methyl-1-butanol than control fruit. [Copyright &y& Elsevier]

Abstract: ‘Big Top’ and ‘Venus’ nectarines and ‘Early Rich’ and ‘Sweet Dream’ peaches were picked at commercial maturity and stored for 20 and 40d at −0.5°C and 92% RH under either air or one of the three different controlled atmosphere regimes (2kPa O2/5kPa CO2, 3kPa O2/10kPa CO2 and 6kPa O2/17kPa CO2). Physicochemical parameters and volatile compounds emission were instrumentally measured after cold storage plus 0 or 3d at 20°C. Eight sensory attributes were assessed after cold storage plus 3d at 20°C by a panel of 9 trained judges, in order to determine the relationship between sensory and instrumental parameters and the influence of storage period and cold storage atmosphere composition on this relationship. A principal component analysis (PCA) was undertaken to characterize the samples according to their sensory attributes. PCA results reflected the main characteristics of the cultivars: ‘Big Top’ was the nectarine cultivar with the highest values for sweetness, juiciness and flavor; ‘Sweet Dream’ was the sweetest peach and was characterized by high values for crispness and firmness, while ‘Venus’ and ‘Early Rich’ were characterized by their sourness. To assess the influence of storage period and CA composition on sensory properties, a PLS model of the flavor of the different samples was constructed using standard quality attributes and volatile concentrations as the X-variables. The model with 2 factors accounted for more than 80% of flavor variance. PLS results indicated that the main influence on flavor perception was storage period. Atmosphere composition also had an influence on flavor perception: flavor perception decreased from samples stored in a 2/5 O2/CO2 atmosphere composition to those of 3/10 and 6/17. These results can be qualitatively extended to juiciness and sweetness since all these sensory properties were strongly correlated. [Copyright &y& Elsevier]

Abstract: Perovskite-type cobaltites LaCo1−x Mg x O3 (0< x ≤0.20) were synthesised by the liquid mix technique and structurally characterised by X-ray diffraction and neutron powder diffraction. This system can be regarded as LaCoO3-derived by means of partial substitution of trivalent cobalt ions by Mg2+. This doping is accompanied by the stabilization of the correspondent amount of Co4+ cations as it has been established from ICP, thermogravimetric and neutron diffraction results. The title materials behave as semiconductors up to 800K. Above this temperature they show a transition to the metallic state. Magnetic susceptibility and magnetization measurements show weak ferromagnetic interactions at 5K which has been interpreted taking into account disordered spin configurations for the cobalt cations. [Copyright &y& Elsevier]

Abstract: This paper presents a complete methodology for the characterization of silver alloys used in modern coin production. Mexican coins with a nominal silver concentration from 10% to 99.99% were used in this study. Calibrated Glow Discharge Optical Emission Spectrometers were used to determine the chemical composition of the alloys as a function of the depth, while inductively coupled plasma was used to determine the total element composition in bulk. Scanning Electron Microscope was used to study the phase distributions in the different silver coins. According to Glow Discharge Optical Emission Spectrometers and inductively coupled plasma, the silver content found in the studied samples was consistently greater than that of the nominal silver content reported by the Mexican mint. This may lead to a review of the new methods of analysis used nowadays in contemporary coin minting. This result is very important because silver is increasing in value as metal and, considering the volume of production of silver coins, this may increase further as a consequence of a growing popular confidence in silver currency. In the case of silver studies, an advantage of the absence of silver detector in the Glow Discharge Optical Emission Spectrometers system is that it allows for the recalibration to have a better range of detection of other metals present in the alloys. A calibration curve using the copper content obtained by inductively coupled plasma (bulk) and Glow Discharge Optical Emission Spectrometers (depth profile) was performed. The relevance of control in modern silver coin minting was clarified, especially in minimizing the discrepancy between the nominal and the core fineness. The physical and chemical properties of the alloys studied are defined, revealing important variations in silver and copper contents. A new methodology and metrology for the control of coinage are suggested. [Copyright &y& Elsevier]

‘Pink Lady®’ apples were harvested at commercial maturity, treated with three different agrochemical products, and stored at 1°C under either air or controlled atmosphere conditions (2kPa O2 +2kPa CO2 and 1kPa O2 +1kPa CO2) for 13 and 27 weeks, followed by 4 weeks storage in air at 1°C. Diphenylamine, folpet and imazalil contents in both the skin and flesh were simultaneously determined after cold storage plus simulated marketing periods of 1 and 7d at 20°C. After 27 weeks plus 7d, diphenylamine and folpet levels in apple skin were lower for fruit stored in low O2 (2kPa) or air than for those kept under ultra-low O2 (1kPa). An additional storage period of 4 weeks in air reduced diphenylamine and folpet contents in whole apples stored for 13 weeks in the low O2 controlled atmosphere. For imazalil, the same result was obtained in apple skins stored for 27 weeks under an ultra-low O2 controlled atmosphere. Differences in diphenylamine and folpet contents were found for skin and flesh samples throughout the simulated marketing period, but there were observable differences in imazalil contents only for flesh samples. [Copyright &y& Elsevier]

Abstract: Freeze-fracture replicas of stallion spermatozoa, collected from the proximal caput, corpus and cauda epididymides regions, were analyzed by electron microscopy to explore the distribution and density of intramembrane particles (IMP). Conspicuous differences in density and arrangement of the IMP were observed in the different topographical domains of mature and immature spermatozoa. A reduction of IMP, especially remarkable in the post-acrosomal domain, was observed in mature epididymal spermatozoa when compared with samples collected from ductuli efferentes. Some structural species-specific differences were also observed. The significance of these changes has not been determined, but remodeling of membrane components during developmental processes constitutes a fine control mechanism to ensure that key molecules are in the correct membrane position and during an appropriate timeframe to mediate fertilization. [Copyright &y& Elsevier]

Abstract: Standard quality parameters, consumer acceptance, and volatile compound emission of ‘Pink Lady®’ apples (Malus × domestica Borkh.) were measured at harvest and after 14 and 25 weeks of cold storage in three different atmospheres. After storage, fruit were left to ripen for 1 and 7 days at 20°C before instrumental and sensory measurements were performed. Data were subjected to principal component analysis (PCA) and partial least square regression (PLSR). PLSR results indicated that the parameters positively influencing acceptability were soluble solid content, titratable acidity, background colour, and emission of hexyl 2-methylbutanoate, hexyl hexanoate, hexyl propanoate, butyl 2-methylbutanoate, 2-methylbutyl acetate and butyl propanoate. Results of sensory analyses revealed the treatments considered in this work could be split into two levels of acceptability. [Copyright &y& Elsevier]

Abstract: SrLaMnTiO6 orthorhombic perovskite has been synthesized by the liquid-mix technique. Structural characterization from X-ray and neutron diffraction shows a random distribution of Mn and Ti atoms. This material shows ferromagnetic ordering with a which can be interpreted in terms of a FM mode along y-axis. A M–I transition and a negative MR response of 90% have been detected at 210 K. AC and DC (ZFC and FC) magnetization measurements show an anomaly at low temperatures which has been attributed to effects of pinning of the FM domain walls rather than SG behaviour. Besides this, linear relation between coercitive field and is interpreted considering the existence of magnetic clusters of the same size embedded in a paramagnetic matrix. Finally the magnetocaloric properties of the title material have been studied and a discrete value of at RT has been found. [Copyright &y& Elsevier]

A series of spinel type derivatives has been obtained from doping the parent compound, Li4/3Ti5/3O4, with Cr3+ giving rise to the phases of general formula Li(1+x)/2TixCr(5−3x)/2O4 (1.07&les;x&les;1.6). X-ray and neutron diffraction refinements confirm that all these phases crystallise in the Fd3m space group, in which Cr3+ ions occupy octahedral sites whereas Ti4+ and Li+ are distributed in both octahedral and tetrahedral sites. Conductivity measurements on polycrystalline samples show that higher substituted samples behave as ionic conductors whereas for the lower limits of substitution the materials are predominantly electronic conductors. Magnetic susceptibility results indicate that the upper doped phases do not show magnetic cooperative interactions but these are significant for the less substituted materials, in which the effective magnetic moment is higher. [Copyright &y& Elsevier]

The electrochemical behaviour in lithium cells of the spinel oxides Li1+yCr1−xAlxTiO4 is reported. This behaviour is based on the structural features and the electrical conductivity of these phases. The mobile Li+ cations are located on tetrahedral 8a sites and the remaining cations (Cr, Al, Ti) on the octahedral 16d ones, and the host materials successfully undergo reversible Li intercalation at 1.5 V, which is attributed to the pair Ti4+/Ti3+. The inclusion of Al3+ in the spinel structure enhances the electrochemical stability of these materials upon cycling although the specific capacity is lowered. [Copyright &y& Elsevier]

[Display omitted] The BiFeO 3 –NaNbO 3 electroceramics, synthesized by the ceramic method, are studied aiming to obtain materials with a well-defined thermistor response coexisting with a relevant magnetic response. XRD data and Raman analysis reveal a structural transition as a function of composition. Compositional features explored from ICP, XPS and EDS measurements, suggest compositional heterogeneity leading to a cluster-type scenario implying NNO-rich and BFO-rich regions in the samples. Impedance spectroscopy data reveal the development of a PTCR thermistor response for x ≥ 0.5 near room temperature. The x = 0.9 ceramic shows resistivity changes of about six orders of magnitude in the first thermal cycle and maximum permittivity values of ∼ 105, much higher than those previously reported for BFO-doped ceramics. Magnetization data are interpreted in terms of the stabilization of superparamagnetic clusters. The response displayed by the x = 0.9 ceramic makes it a promising multifunctional material for device applications. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • A composite material with fly ash, alkali, sol-gel solution and heat treated was prepared. • A cellular cement-like light material was obtained. • Sol-gel solution had waterglass plus silica nanoparticles to be geopolymerized with fly ash. • Cenospheres were dissolved with an alkali and the resulting material used as pozzolan material. • This light-concrete type material did not included cement. Abstract The rise of sustainability marks a trend towards the formulation of alternative materials that allow the production of eco-friendly cementitious mixtures, thus preserving natural resources. Therefore, this work proposes the elaboration of composite materials based on fly ash with cementitious characteristics when using an alkaline sol-gel solution in a process with thermal treatment. The sol-gel solution was distinctive to be composed of sodium silicate in water or waterglass and a component of silica nanoparticles. The dissolution reaction that sodium hydroxide or some other, effects on the thermally treated fly ash generates a composite material characterized by a great porosity at the same time of cohesion in its structure that gives it rigidity. The materials obtained were characterized by X-Ray Diffraction (XRD), Confocal Laser Scanning Microscopy (LSCM), Scanning Electron Microscopy (SEM), Differential Scanning Calorimetry (DSC) and mechanical compression resistance tests. The results of the tests of resistance and the elaborated analyzes reflect that it is possible to form a light material with the properties similar to those of the ordinary Portland cement. [ABSTRACT FROM AUTHOR]

The electroceramics of the x NaNbO 3 - (1-x) BiFeO 3 (x = 0.15, 0.25, 0.50, 0.75, 0.85, 1) system (NBNFO) have been prepared at moderate temperatures (600 °C). Microstructural analysis from high resolution electron microscopy reveals the existence of small crystals (10–150 nm), which agglomerate leading to micro-sized crystals. All the NBNFO compounds show perovskite-type structure and a transition from rhombohedral (S.G. R 3 c ) to orthorhombic (S. G. P 2 1 ma ) mean macroscopic symmetry takes place for x = 0.50, as analyzed by refinement of XRD data. Nevertheless, at the microstructural scale, the system can be described by a compositional-segregation picture in which structural heterogeneity is present. The materials show a positive temperature coefficient of resistivity (PTCR)-thermistor behavior above room temperature for x ≥ 0.50, up to maxima temperature values of 410, 393, 405 and 463 K for x values of 0.50, 0.75, 0.85 and 1, respectively. Above these temperatures, in the NTCR temperatures-region, conduction and polarization phenomena are analyzed from impedance and modulus formalisms in terms of two mechanisms implying different charge carriers: polaron hopping and/or diffusion of cation and oxygen vacancies. The activation energy values, E a , corresponding to these processes are of about 0.50 and 1 eV, respectively. Finally, in the dielectric response displayed by the NBNFO ceramics, the development of a FE contribution as x increases is detected, which can be interpreted considering microstructural features. [ABSTRACT FROM AUTHOR]

Two new phases in the (SrTiO 3 )-(BiMnO 3 ) perovskite type system were studied. These SrBiMn 2−x Ti x O 6 ( x =0.5 and 0.75) ceramics were prepared by the liquid-mix method as polycrystalline powders. They were characterized by neutron diffraction (ND), electrical and magnetic measurements and these results were analysed in connection with the x =0.25 phase, previously described by us. Their crystal structures were fitted in the tetragonal I 4/ mcm space group, with additional superstructure reflections suggesting local ordering. Electron microscopy results revealed these ordering effects are actually present concerning both perovskite sublattices. The electrical response pointed to a mechanism consisting in variable range hopping of polarons. A relaxor ferroelectric behaviour dependent on the pellets thickness was found with T m in the 140–240 K range. The magnetic structures imply an incommensurable modulation of the magnetic moments along the c or a directions, depending on the substitution degree x . A cluster picture in terms of chemically different nanoregions responsible of the macroscopic response is discussed. [ABSTRACT FROM AUTHOR]

Microcrystalline powders of the Sr 2− x Bi x Ti 2− x Fe x O 6± δ ( x =0.25; 0.50; 0.60; 0.75; 1; 1.25) perovskites have been prepared by the liquid-mix technique and the SrBiTi 2− x Fe x O 6 ( x =0.85) sample was obtained by the ceramic method. Rietveld refinements from X-ray powder diffraction data showed a structural transition as a function of x : cubic symmetry (S.G. Pm 3 m ) is observed for x ≤1 whereas the x =1.25 sample presents rhombohedral symmetry (S.G. R 3_ c ). Refined occupations and EDX analyses indicate that the obtained cationic compositions are close to the nominal ones for the Sr 2− x Bi x Ti 2− x Fe x O 6± δ samples but a small cationic deficiency was detected in the sample obtained by the ceramic method. Particle sizes of about 200 nm were obtained for the samples obtained by the liquid mix technique whereas they were clearly micrometric for the x =0.85 sample, obtained by the ceramic method. HRTEM analysis showed that these greater in size crystals present high degree of microstructural disorder. The dielectric response seems to be related to a relaxor-type ferroelectric behavior. Capacitance, conductivity and tangent loss values indicate the prevalence of intergrain conductive contribution in the electrical response. The results are comparatively analyzed in relation to microstructural features and the synthesis method employed. [ABSTRACT FROM AUTHOR]

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: Emission of aroma volatile compounds and some related enzyme activities (LOX, PDC, ADH, and AAT) were assessed in ‘Fuji’ apples (Malus × domestica Borkh.) during shelf life at 20°C following cold storage under air or under three different CA conditions (3kPa O2:2kPa CO2; 1kPa O2:1kPa CO2; or 1kPa O2:2kPa CO2). Data were used for principal component analysis (PCA) and partial least-square regression (PLSR) analysis of results. LOX activity was partly inhibited by hypoxic conditions, and thus could have contributed to differentiation between air- and CA-stored fruit. Accordingly, emission of straight-chain esters was also higher in air- than in CA-stored fruit. In contrast, PDC activity was responsible for part of the differences between low (3kPa) and ultra-low (1kPa) O2 storage conditions, probably by providing substrates for AAT action. AAT activity afforded no satisfactory differentiation between samples, and therefore it is suggested that substrate availability is a more decisive factor than enzyme activity for volatile production after storage. The PCA and PLSR models developed in this work were not useful for discrimination between the two studied ultra-low O2 conditions. [Copyright &y& Elsevier]