Caracterização de fragmentos cerâmicos de Terra Preta de índio.

Abstract

The combination of spectroscopy and Fourier transform infrared (FT-IR), XRD and Mössbauer spectroscopy has considerable potential in studying the chemical and physical transformation that occur in ceramic bodies during firing. Ceramic fragment samples from archaeological sites in the Amazon region were collected and submitted to analysis by Mössbauer spectroscopy, X-ray diffraction, infrared spectroscopy and Ramam Fourier transform. The analysis results of X-ray diffraction indicated the presence in extracts magnetic, hematite, iron oxides and quartz, and also detected the presence of a mixture formed by isomorphous titanium oxides. The magnetic spectra of the extracts at room temperature were fitted to two sextets and a doublet. The doublets indicate the presence of hematite or maghemite in superparamagnetic state or the presence of Fe3+ in silicate structure. Mössbauer parameters obtained for Clean Water, Costa Conceicao, Oriximiná Parintins and revealed the existence of maghemite (inner sextet) and hematite (outer sextet). A sextet of procedure for the fragments collected in Iranduba present values of field distribution typical of magnetite. In all spectra the parameters of the doublets are characteristic of paramagnetic Fe3+.The curves of probability distribution of the magnetic field of the ceramic samples are characterized by different profiles, the distribution of hyperfine field shows up between 490 and 512 T in the Mössbauer spectra. The maximum probability hyperfine field distribution existing in the spectra is present in the region of 512 Tesla associated with isomer shift and quadrupole. The distribution of hyperfine field varied considerably in the range 330-520 T. Depending on the piece of archaeological pottery are seen various maximum likelihood.