Partial characterization of Vitis vinifera grapes var. Ancellotta

Abstract Freezing point depression and some physical characteristics of Vitis vinifera grapes var. Ancellotta were investigated after two different post-harvest treatments of samples (slow air-freezing at −18°C and storage at 2°C in N 2 atmosphere). The measured acinus mean weight and diameter, relative weight composition of a cluster and total soluble solids content differed slightly from those of fresh grapes. The observed freezing point depression values for treated grapes and grape juice were smaller than the respective calculated data. The differences were characterized by alteration in soluble solids composition due to the treatments, which decreased solute-solvent interactions

Weak ferromagnetism and spin reorientation in antiferroelectric BiCrO3

BiCrO3 is an antiferroelectric perovskite known to exhibit an unconventional spin reorientation transition between antiferromagnetic structures, accompanied by a large jump in weak ferromagnetism. Using a combination of neutron powder diffraction, magnetometry, and symmetry analysis, we confirm the dominant G-type antiferromagnetic order below TN = 111 K and identify the magnetic phase transition with a spontaneous rotation of Cr3+ moments from the b axis to a particular direction in the ac plane. We demonstrate the role of antiferroelectric displacements produced by the Bi3+ lone-pair electrons and octahedral rotations in establishing spin canting via the antisymmetric Dzyaloshinskii-Moriya interaction. This mechanism results in weak ferromagnetism above and below the spin-reorientation and explains the dramatic increase in net magnetization on cooling

Thermally activated magnetization reversal in bulk BiFe0.5Mn0.5O3

We report on the synthesis and characterization of BiFe0.5Mn0.5O3, a potential type-I multiferroic compound displaying temperature induced magnetization reversal. Bulk samples were obtained by means of solid state reaction carried out under the application of hydrostatic pressure at 6 GPa and 1100{\deg}C. The crystal structure is an highly distorted perovskite with no cation order on the B site, where, besides a complex scheme of tilt and rotations of the TM-O6 octahedra, large off-centering of the bismuth ions is detected. Below T1 = 420 K the compound undergoes a first weak ferromagnetic transition related to the ordering of iron rich clusters. At lower temperatures (just below RT) two distinct thermally activated mechanisms are superimposed, inducing at first an enhancement of the magnetization at T2 = 288 K, then a spontaneous reversal process centered at T3 = 250 K, finally giving rise to a negative response. The application of fields higher than 1500 Oe suppresses the process, yielding a ferromagnetic like behaviour. The complementary use of SQuID magnetometry and M\"ossbauer spectroscopy allowed the interpretation of the overall magnetic behaviour in terms of an uncompensated weak competitive coupling between non-equivalent clusters of interactions characterized by different critical temperatures and resultant magnetizations. PACS numbers: 75.85.+t, 75.60.Jk, 76.80.+y, 75.30.Et, 75.30.KzComment: 30 pages, 13 figure

Low temperature specific heat of densified vitreous B2O3

Low temperature specific heat of densified vitreous B2O

Progress on Low-Temperature Pulsed Electron Deposition of CuInGaSe2 Solar Cells

The quest for single-stage deposition of CuInGaSe2 (CIGS) is an open race to replace very effective but capital intensive thin film solar cell manufacturing processes like multiple-stage coevaporation or sputtering combined with high pressure selenisation treatments. In this paper the most recent achievements of Low Temperature Pulsed Electron Deposition (LTPED), a novel single stage deposition process by which CIGS can be deposited at 250 °C, are presented and discussed. We show that selenium loss during the film deposition is not a problem with LTPED as good crystalline films are formed very close to the melting temperature of selenium. The mechanism of formation of good ohmic contacts between CIGS and Mo in the absence of any MoSe2 transition layers is also illustrated, followed by a brief summary of the measured characteristics of test solar cells grown by LTPED. The 17% efficiency target achieved by lab-scale CIGS devices without bandgap modulation, antireflection coating or K-doping is considered to be a crucial milestone along the path to the industrial scale-up of LTPED. The paper ends with a brief review of the open scientific and technological issues related to the scale-up and the possible future applications of the new technology

High pressure and multiferroics materials: a happy marriage

The community of material scientists is strongly committed to the research area of multiferroic materials, both for the understanding of the complex mechanisms supporting the multiferroism and for the fabrication of new compounds, potentially suitable for technological applications. The use of high pressure is a powerful tool in synthesizing new multiferroic, in particular magneto-electric phases, where the pressure stabilization of otherwise unstable perovskite-based structural distortions may lead to promising novel metastable compounds. The in situ investigation of the high-pressure behavior of multiferroic materials has provided insight into the complex interplay between magnetic and electronic properties and the coupling to structural instabilities

Method for producing thin-film multilayer solar cells

Description: A method for manufacturing high-quality thin film solar cells entirely by the Pulsed Electron Deposition (PED) is presented. The solar cell is a multi-layer architecture composed with an absorber layer with a chalcopyrite structure and the general composition Cu (In, Ga, Al) (Se, S)2 or CIGASS, deposited on a metallic substrate, that is the lower electrical contact or "back contact", by one or more buffer layer(s) and a layer acting as an electrical contact or the higher "top contact". The novelty of this process are: 1) The absence of layers containing cadmium (Cd) in the solar cell; 2) The deposition of the absorber layer, of the buffer layer(s) and of the top ohmic contact can be made sequentially using the same high-energy electron pulsed system, alternating only the target where the beam focuses and the energy of the electron beam. Main applications: The method described in the patent can be useful in the photovoltaic field, in particular for the fabrication of "2nd generation solar cells" or thin film solar cells. Main Advantages: The novelties introduced in this patent are: 1) Ability to deposit every layer using the same pulsed electron source. 2) Capability to deposit the absorber layer (CIGASS) using a single stage. 3) Ability to grow cadmium-free buffer layers, resulting in a totally eco-compatible solar cell.Descrizione: E\u27 presentato un metodo per produrre celle solari a film sottile di alta qualit? strutturale ottenute interamente mediante tecnica di deposizione da elettroni pulsati (PED). La cella solare a multistrato ? composta da uno strato assorbitore di fase calcopirite con composizione generica Cu(In,Ga,Al)(Se,S)2 o CIGASS, depositato su un substrato metallizzato che costituisce il contatto elettrico inferiore o "back contact", da uno o pi? buffer layer(s) e da uno strato che funge da contatto elettrico superiore o "top contact". Le novit? di questo processo sono: 1) Non ? previsto l\u27utilizzo di strati contenenti cadmio (Cd); 2) Le deposizioni dello strato assorbitore, del/dei buffer layer(s) e del contatto ohmico superiore possono avvenire sequenzialmente utilizzando lo stesso sistema a elettroni pulsati ad alta energia, alternando esclusivamente il target su cui va a incidere il fascio tra uno stadio di deposizione e il successivo e modificando l\u27energia del fascio elettronico. Usi Principali: Il metodo del trovato pu? essere utilizzato nel campo fotovoltaico per ottenere le cosiddette "celle di 2a generazione o a film sottile". Vantaggi Principali: Gli elementi di innovazione introdotti dal trovato sono i seguenti: 1) Possibilit? di depositare ogni strato mediante la stessa sorgente di elettroni pulsati. 2) Possibilit? di depositare lo strato assorbitore (CIGASS) mediante un unico stadio. 3) Possibilit? di depositare buffer layer senza cadmio, ottenendo una cella solare totalmente eco-compatibil

High pressure induced insulator-to-semimetal transition through intersite charge in NaMn7O12

The pressure-dependent behaviour of NaMn7O12(up to 40 GPa) is studied and discussed by means of single-crystal X-ray diffraction and resistance measurements carried out on powdered samples. A transition from thermally activated transport mechanism to semimetal takes place above 18 GPa, accompanied by a change in the compressibility of the system. On the other hand, the crystallographic determinations rule out a symmetry change to be at the origin of the transition, despite all the structural parameters pointing to a symmetrizing effect of pressure. Bond valence sum calculations indicate a charge transfer from the octahedrally coordinated manganese ions to the square planar ones, likely favouring the delocalization of the carriers