Produção Nacional
Revisado por pares
Irradiation and heating effects in amethyst crystals from brazil
1991; Taylor & Francis; Volume: 117; Issue: 4 Linguagem: Inglês
10.1080/10420159108220755
ISSN1042-0150
AutoresClemencio Teodoro Dotto, Sadao Isotani,
Tópico(s)Cultural Heritage Materials Analysis
ResumoAbstract In this work we report optical absorption spectroscopy study of thermal and irradiation effects on samples of amethyst from Minas Gerais and Rio Grande do Sul, Brazil. Three bands were studied: 10500 cm−1 (k), 18300 cm−1 (θ) and 28000 cm−1 (ζ). Thermal and irradiation effects shows that the θ and ζ bands belongs to a same center and the k band to another center. The isothermal decay and irradiation growth of these band reveal a complex kinetics. The optical absorption bands of amethyst from Minas Gerais do not recover the prmitive absorbance after being bleached at 470°C and irradiated. This sample heated at 470°C in highly reducing atmosphere gets a yellow-brown color. The amethyst from Rio Grande do Sul treated at 400°C gets, also, a yellow-brown color. We suggest this color is probalbly due to the formation of Fe2O3 submicroscopc segregate crystals due to the diffusion of Fe ions and oxygen vacancies. Key Words: amethystirradiationthermal treatmentoptical absorption
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