Classification of ancient Etruscan ceramics using statistical multivariate analysis of data

About one hundred Etruscan ceramic shards dating from the VIII to the IV century BC and coming from the archaeological excavation at Pian di Civita in Tarquinia (central Italy) have been analyzed by inductively coupled plasma optical emission spectrometry and flame atomic emission spectrometry in order to settle their provenance and to acquire knowledge about the ceramic production technology. The examined shards belong to the class of the depurata pottery, a fine ware produced in Tarquinia over a long period, and are representative of different sub-classes. The samples have been analyzed for fifteen elements (Ca, Al, Mg, Fe, Ti, Cr, Cu, Ni, Zn, Mn, Zr, Sr, Na, K and Rb). The data acquired have been treated by multivariate analysis techniques such as principal component analysis and Kohonen artificial neural networks. Most of the analyzed shards have been locally produced as belonging to a unique large group. A continuity in usage of both choice of materials and technology has been recognized. PACS 02.50.Sk; 81.05.Mh; 82.80.-d     

Magnetocaloric properties of La<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript>K<Emphasis Type="Italic">x</Emphasis>MnO<Subscript>3</Subscript> manganites

A technology for obtaining single-phase ceramic samples of La_{1 − x} K _x MnO₃ manganites, as well as the dependence of their structure parameters on the potassium content, is described. The magnetocaloric effect in the samples has been measured by two direct methods, the classical method and the magnetic field modulation method, and has been calculated from the specific heat data. The values of the magnetocaloric effect obtained by these methods are significantly different. The observed discrepancies have been explained. Correlation between the doping level and the value of the effect has been found. It has been shown that the magnetic-field dependence of variation of the magnetic entropy near T _C in weak fields corresponds to theoretical calculations and that the value of the magnetocaloric effect in high magnetic fields can be predicted using this dependence.     

Polyenic pigments from the Brazilian octocoral Phyllogorgia dilatata Esper, 1806 characterized by Raman spectroscopy

Phyllogorgia dilatata is a Brazilian endemic gorgonian with a natural color ranging from white to pale yellow. An unusual violet pigmentation has been observed in colonies with tissue damage and skeleton anomalies. In order to investigate the chemical composition of these pigments, we have used in situ Raman spectroscopy to characterize the white/cream and violet tissues as well as sclerites, a skeletal component consisting of calcite, from both samples. Violet/purple pigmentation surrounding tissue necrosis is characterized as purpling, in response to fungus infection and allelopathic interactions. The spectroscopic analysis of the white‐cream tissues, designated as healthy, has revealed the presence of the carotenoid peridinin, typical of the endosymbiont that harbors this species; however, peridinin was not observed in the colorless sclerites analysis, presenting bands exclusively of calcite. In contrast, the violet coloration of damaged tissue has also been observed in the sclerites. Both showed Raman bands corresponding to unmethylated polyunsaturated aldehyde, besides calcite bands. This is the first report of purpling in a Brazilian octocoral, identified as a derivative of the biochromes named psittacofulvins, which have been reported as exclusive in parrots. Copyright © 2011 John Wiley & Sons, Ltd.     

Phase transformations in calcite from electrical impedance measurements

The phase transformation in calcite I-IV-V and calcite ? aragonite have been characterized by electrical impedance measurements at temperatures 600–1200°C and pressures 0.5–2.5?GPa in a piston cylinder apparatus. The bulk conductivity σ has been measured from Argand plots in the frequency range 10⁵–10^?2?Hz in an electric cell representing a coaxial cylindrical capacitor. The synthetic polycrystalline powder of CaCO₃ and natural crystals of calcite were used as starting materials. The transformation temperature T_c was identified from resistivity-temperature curves as a kink point of the activation energy. At pressure above 2?GPa in ordered phase calcite I, the activation energy E _σ is c. 1.05?eV, and in disordered phase calcite V E _σ is c. 0.75?eV. The pressure dependence of T_c for the rotational order–disorder transformation in calcite is positive for pressures <1?GPa and negative for pressures >1?GPa. The transformation boundary of calcite 1–IV is observed only during first heating in samples after a long annealing at low temperatures. The activation energy of calcite I???IV decreases gradually from 1.8 to 1.05?eV with the pressure increase from 0.5 to 2?GPa. The kinetics of calcite ? aragonite transformation has been monitored by measuring a time-variation of the electrical resistance of a calcite sample at 10³?Hz in the stability P-T field of aragonite. The variation of the impedance correlates with the degree of phase transformation, estimated from X-ray powder diffraction studies on quenched products of experiments. The kinetics of calcite ? aragonite transformation may be fitted to the Avrami kinetics with the exponent m???1–1.5.     

Features of interfaces in layered La<Subscript>2 − <Emphasis Type="Italic">x</Emphasis></Subscript>Sr<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>CoO<Subscript>4</Subscript> oxides: Products of solid-state synthesis

The interfaces in complex La_{2 − x} Sr _x CoO₄ oxides (0.1 < x < 1.5) obtained by the ceramic method were studied in detail. To determine the chemical composition of the interfaces and their effect on the properties of ceramics, the magnetic and electric properties were investigated and X-ray phase and micro X-ray analyses were performed. It was found that the mechanical stability of the samples is determined by the presence of lanthanum in the surface layer.     

The nature of marbled Terra Sigillata slips: a combined μXRF and μXRD investigation

In addition to the red terra sigillata production, the largest Gallic workshop (La Graufesenque) made a special type of terra sigillata, called “marbled” by the archaeologists. Produced exclusively at this site, this pottery is characterized by a surface finish made of a mixture of yellow and red slips. Because the two slips are intimately mixed, it is difficult to obtain the precise composition of one of the two constituents without contamination from the other. In order to obtain very precise correlation at the appropriate scale between the color aspect and the elemental and mineralogical phase distributions in the slip, combined electron microprobe, X-ray micro spectroscopies and micro diffraction on cross-sectional samples were performed. The aim of this study is to discover how potters were able to produce this unique type of terra sigillata and especially this particular slip of an intense yellow color. Results show that the yellow component of marbled sigillata was made from a titanium-rich clay preparation. The color is due to the formation of a pseudobrookite (TiFe₂O₅) phase in the yellow part of the slip, the main characteristics of that structure being considered nowadays as essential for the fabrication of stable yellow ceramic pigments. Its physical properties such as high refractive indices and a melting point higher than that of most silicates widely used as ceramic colorants are indeed determinant for this kind of application. Finally, the red parts have a similar composition (elementary and mineralogical) to the one of standard red slip.     

ESR studies on calcite encrustation on Fili neotectonic fault, Greece

Electron spin resonance (ESR) study was done on calcite encrustation on Fili neotectonic fault surface, Greece. Normally such calcite encrustations on fault surfaces are not observed. Significantly, the ESR study has detected the presence of nitrate NO₃²⁻ radical in this calcite encrustation, havingg _⊥=2.0063±0.0001 and hyperfine coupling constantA _⊥=3.44 mT, the second such detection of nitrate NO₃²⁻ radical following a sample from Scott Glacier, Antarctica. From isochronal thermal annealing measurement the NO₃²⁻ radical was found to be quite stable, only fully annealed at 475°C. This study also shows that the ESR, as a tool, can be suitably applied to date the age of formation of the calcite encrustation with SO₃⁻ as an ESR dating signal by additive γ-ray irradiation. A preliminary estimation indicates the age of formation of calcite precipitation at Fili fault, Greece to be about 5600 years.     

Photoluminescence linewidth broadening due to alloy/thickness fluctuation of CdxZn1 − xSe/ZnSe triple quantum wells

Photoluminescence (PL) linewidth broadening of Cd_xZn_{1 − x}Se/ZnSe triple quantum wells, grown on GaAs substrates by molecular beam epitaxy (MBE), has been investigated. Various quantum well (QW) samples have been prepared with different QW thickness and composition (Cd-composition). Measured and calculated PL linewidth are compared. Both composition and thickness fluctuations are considered for the calculation with the parameters such as the volume of exciton, nominal thickness and composition of QWs. Surface roughness measured by atomic force microscopy (AFM) is used to estimate the interface roughness. Results show that when Cd-composition increases additional linewidth broadening due to Zn/Cd interdiffusion is enhanced.     

Determination of the Breakage and Wetting Parameters of Calcite and Their Correlations

This paper presents the breakage and wetting parameters of calcite mineral obtained experimentally and establishes a correlation between these characteristic parameters. The breakage parameter obtained from the different feed sizes of grinding is the specific rate of breakage (S_i). The wettability parameter, obtained from surface chemistry‐based processes such as contact angle measurements or flotation methods, is the critical surface tension of wetting of a solid or mineral (γ_c). Calcite mineral, studied for the determination of the above parameters and their correlations, was ground in a laboratory‐size ceramic ball mill with dry, wet and chemically aided grindings and tested extensively to determine the γ_c values by using a contact angle goniometer and a newly designed micro‐column flotation cell. The highest S_i value obtained was 0.35 min^?1 for sodium dodecyl sulfate (SDDS)‐aided grinding, and the lowest S_i value was 0.26 min^?1 for dry grinding of the ?600+425 feed in the mill. The γ_c values for calcite were obtained as 34.0–34.9 mN/m for SDDS‐treated calcite surfaces, 29.9–31.4 mN/m for sodium oleate‐treated surfaces and >72 mN/m for both dry and wet ground products whose surfaces were not treated chemically. Some correlations were established between the S_i and γ_c parameters; as the S_i increases, γ_c decreases, indicating that relatively more hydrophobic surfaces are broken faster for the largest sizes, resulting in higher S_i values with more fines (lower γ of B_{i, j}) in the finer size distribution region (i.e. ?150 μm).     

The effect of heat treatment on the thermoluminescence of naturally-occurring calcites and their use as a gamma-ray dosimeter

The feasibility of using naturally-occurring calcite for gamma-ray dosimetry was investigated. Anneal treatment above 350°C increased the sensitivity of all radiation-induced TL peaks except the glow peaks above 300°C. On the other hand, annealing in air, at a temperature of 700°C caused a collapse in the TL sensitivity. The increase in TL efficiency was found to depend on the annealing temperature and time. Heating at 600°C for 5 h and quenching in ambient air are the optimum conditions for TL sensitivity enhancement in the calcite materials investigated. These results are explained using the energy scheme of the pre-dose model of Zimmerman (1971) and in terms of the impurity rearrangements in the crystal lattice induced by heating. It was found that the values of the kinetic parameters E, s and b for TL glow peaks remained unchanged for annealed samples. The TL dose–response curves for stable dosimetric peaks of annealed and unannealed calcite samples could be fitted to the same linear mathematical function. This implies that the annealing process probably does not change the nature of the trapping centers except the low temperature TL peaks at 125 and 160°C of flowstone. The TL dosimetric parameters of calcite samples annealed, including glow curves, fading characteristics, dose–responses, dose-rate responses and energy responses, have also been studied in detail. The response to gamma-rays of annealed calcite samples was found to be linear from 0.05 to 10⁴ Gy. The lower limit of observable doses for each calcite sample was about 0.05 Gy. This offers the possibility of applying the investigated materials for gamma-ray dosimetry within this useful range. These dosimeters can be used in various applications, such as, in industries related to chemical technology (polymerization), food processing and in determining the dose received by the patient during medical examination and treatment.     

Effect of a bias field on the dielectric properties of NaNbO3 solid solutions in the range of the giant temperature hysteresis of a phase transition

The effect of a bias field E on the value and temperature dependence of permittivity ɛ of ceramic samples of solid solutions 0.6NaNbO₃-0.4 NaTaO₃ (I), and 0.97[0.9NaNbO₃-0.1Na_0.5Bi_0.5TiO₃]-0.03LiNbO₃ (II) possessing an anomalously large temperature hysteresis of ɛ(T) dependence is studied. The character of the dependences of both the height and the temperature of the ɛ(T) maximum on the field show that composition (I) has antiferroelectric properties, while composition (II) has ferroelectric properties. It is found that up to 8 kV/cm, the strength of the bias field has actually no effect on the width of the ɛ(T) temperature hysteresis of the compositions under study.     

New Raman Spectroscopic Data of the Almahata Sitta Meteorite

The archaeological site of Pintia (Padilla de Duero/Peñafiel, Valladolid), considered one of the first cities on the Iberian Peninsula, has yielded very interesting archaeological records regarding the different functional areas that involve the oppidum. Pottery, metal, and bone/skeletal remains are very well preserved, being optimal for analysis and study of the ancient food contained, such as milk-based products, animal fats, beer, and wine. The combination of Raman Microscopy (RM) with other analytical techniques such as Light Microscopy (LM) and Environmental Scanning Electron Microscopy equipped with Energy Dispersive X-ray Spectroscopy (ESEM-EDX) becomes a powerful tool to obtain information on the possible content in the ceramic receptacles from historical-archaeological heritage. It can lead to an interpretation of their specific use or functionality. In this work, a unique sample preparation was used for all techniques, which lead to a very simple procedure and documentation. The degradation and aging of natural fibers and the presence of organic matter with low crystallinity and calcium oxalate–related residuals can be studied by these combined techniques. The archaeological residuals can be separated from modern contamination coming from agriculture processes, surrounding land minerals, or fresh vegetal matter.     

Diffuse phase transition of BaTi0.6Zr0.4O3 relaxor ferroelectric ceramics

BaTi_0.6Zr_0.4O₃ ceramic was prepared through solid state reaction route. X-ray diffraction showed that the composition has cubic perovskite structure with space group Pm-3m at room temperature. Temperature dependency dielectric study of the ceramic has been investigated. Bulk density was determined using Archimedes principle and found to be ～97% of X-ray density. The average grain size in the pallet is measured by an optical microscope and found to be 22.23?µm. The dielectric measurement revealed diffuse phase transition of second-order, where dielectric peak temperature (T _m) is dependent of frequency showing relaxor-type behaviour. A clear deviation from Curie–Weiss law is observed in the paraelectric region. The dielectric relaxation rate follows the Vogel–Fulcher relation with E _a?=?0.1020?eV, T _f?=?106?K, ν₀?=?8.5?×?10¹¹?Hz.     

Precious coral non‐destructive characterization by Raman and XRF spectroscopy

Precious corals are some of the most valuable living marine resources, growing and commercially exploited only in limited areas of the world, namely the Mediterranean Sea and the Northern Pacific Ocean. Their skeleton is formed by calcium carbonate crystallized in the form of calcite whereas their color is because of the presence of partially demethylated polyene pigments. Recently, Pacific corals have been included in the appendix II of CITES list, while Mediterranean corals are still excluded. Different Corallium species of Corallidae family (e.g. Corallium rubrum, Corallium elatius and Corallium secundum) collected from different locations of the Mediterranean Sea and the Pacific Ocean were analyzed by Raman spectroscopy for the characterization of the reddish pigment and by X‐ray fluorescence (XRF) for the determination of the chemical composition of their skeletons, in order to obtain molecular and elemental data with two relatively easy and non‐destructive techniques, which can be used quite steadily for authentication purposes. Raman analysis demonstrated the presence of specific vibrational bands useful to identify the colored pigments as a mixture involving methylated and demethylated polyenes such as carotenoids and parrodienes, characterized by the presence of ―CH₃ groups along the polyene chain. The ratio between the Raman signal and fluorescence background was found to vary as a function of the macroscopic color of the coral, but Raman analyses resulted inadequate for distinguishing between corals having similar color but different origins. On the other side, XRF data provided reliable information for an appropriate separation between Pacific and Mediterranean corals at the elemental level. The results of this study will be of great relevance for the authentication and identification of the origin of corals in trade market by means of completely non‐destructive techniques. Copyright © 2016 John Wiley & Sons, Ltd.     

Influence of grain boundaries on resistivity of manganites La1 − x K x MnO3

Results of investigation of resistivity and magnetoresistance of manganites La_{1 − x} K _x MnO₃ (x = 0.050–0.175) are presented. Behavior of resistivity ρ(T) in the paramagnetic and ferromagnetic phases has been described. To describe ρ(T) near the phase-transition temperature, notions of the percolation theory have been used. Two maxima have been found in the dependence ρ(T); their appearance has been attributed to the ceramic nature of the studied samples. The observed increase in magnetoresistance with a decrease in temperature is caused by intergranular spin-polarized tunneling of charge carriers.     

Investigation of the closed porosity of functional ceramic materials by spin-echo small-angle neutron scattering

The closed porous structure in ceramic materials is investigated by spin-echo small-angle neutron scattering. A series of ceramic samples of oxygen–ion conductors based on bismuth molybdate with the general formula Bi_12.8 X _0.2Mo₅O_{34 ± δ} (X = Mg, Ba, Ca, Sr) is obtained by powder sintering for 6?45 h at a temperature close to the melting point. The samples are characterized by scanning electron microscopy and X-ray fluorescence analysis. It is found that they had a stoichiometric chemical composition, are singlephase, and contain clean pores between crystal grains. The pore size is determined by spin-echo small-angle neutron scattering and ranges from 2.2 to 3.5 μm. It is demonstrated that longer sintering times correspond to larger pores (the increase in their average diameter is as large as 30%). It is found that the studied materials lack a fractal pore structure.     

Specific features in the synthesis, crystal structure and electrical conductivity of BICUTIVOX

The formation of solid solutions Bi₄V_2 − xCu_x/2Ti_x/2O_11 − x (0.025 ≤ x ≤ 0.5) known as BICUTIVOX, synthesized by three different methods (a conventional solid-state synthesis, solid-state synthesis enhanced by mechanical activation, and through liquid precursors), has been studied. Based on crystal structure investigations carried out at different temperatures, ranges of stability and temperatures of phase transitions for different polymorphous modifications have been defined. The morphology and the local chemical composition of the ceramic samples obtained have been studied. Thermal expansion coefficients have been measured. The electrical conductivity of ceramic samples has been investigated in a wide range of temperatures and partial oxygen pressures.     

Raman microscopy of prehistoric paintings in French megalithic monuments

Remains of pictorial decorations in a series of six representative megalithic monuments of Brittany (France) and two French stelae have been studied by micro‐Raman spectroscopy for the first time. Fungal colonies on the painted orthostats made it difficult to obtain in situ Raman spectra of the paint components. Nevertheless, paint micro‐specimens studied in the laboratory by micro‐Raman spectroscopy, X‐ray photoelectron spectroscopy and scanning electronic microscopy combined with energy dispersive X‐ray spectroscopy have made possible to characterise the materials present. The minerals α‐quartz, albite, microcline, muscovite, phlogopite, celadonite, beryl and anatase have been identified in the granitic rocks supporting the paintings, while dolomite and calcite are dominant in the calcareous rocky substrata. Haematite is the main component of the red pictographs, whereas amorphous carbon and manganese oxides/oxihydroxides have been used in the black ones. Calcite, gypsum and amorphous carbon have been detected as additional components of the paint in some cases. Contamination with modern tracing materials (polystyrene and ε‐copper‐phthalocyanine blue) has been detected in several cases. The presence of pigments as decorative elements in megalithic monuments of Western France and its possible relation with those of the Iberian Peninsula create interesting expectations for the knowledge of the European megalithic culture. Copyright © 2015 John Wiley & Sons, Ltd.     

Mytilus galloprovincialis as a bioindicator of environmental conditions: the case of the eastern coast of the Adriatic Sea

The marine mussel Mytilus galloprovincialis lives attached to the surface of hard substrata, where its exposure and relative immobility allow it to record changes in ambient seawater. It is also found along the eastern coast of the Adriatic Sea. Oxygen and carbon isotopes were analysed for calcite and aragonite in separate shell layers, while major, minor and trace elements in the bulk shell were analysed to evaluate environmental conditions such as the temperature of carbonate deposition, freshwater influence and locations of anthropogenic pollution. We found that, on average, aragonite is enriched by 1.1‰ in ¹³C and by 0.2‰ in ¹⁸O compared with calcite. The calculated temperatures for M. galloprovincialis shell growth from the investigated area range from 13.4 to 20.9 °C for calcite and from 16.6 to 23.1 °C for aragonite. According to the δ¹⁸O and δ¹³C values of shell layers, we can separate the investigated area into three locations: those with more influence of freshwater, those with less influence of freshwater and those with marine environments. The highest concentrations of manganese, barium, boron, arsenic, nickel and chromium were observed in shells from Omi?, Ba?vice and Zabla?e (Central Adriatic) and Sv. Ivan (South Adriatic), where chemical and heavy industries are located and where sewage is known to be discharged into coastal areas. The highest concentrations of zinc, lead and copper were measured in samples from Pula, Rijeka and Gru?, where there are also ports in addition to industry.