Investigation of optical, paramagnetic and luminescence properties on natural Brazilian silicate crystals due to point defects

Abstract

Natural mineral crystals contains invariably, several impurities. At first look, therefore there can be difficulties to investigate their physical properties. The results found in some studies, however, show that for a given property of interest usually one, two or three species of foreign atoms are important, the remaining impurities are not, although, could be for other properties of the crystal. There is still other factor such as depending on the origin of mineral there can be variation in the concentration of impurity that is of interest. Nevertheless, with techniques available for determination of concentration of impurities, it is not difficult to investigate the dependence of a given property on the impurity content. The first reason for the present project is exactly the above fact. Optical absorption, luminescence and paramagnetic resonance(both electron and nuclear) properties of natural silicate crystals, whose investigation is the objective of the present project, usually depend only on two or three impurities, making the project to be carried out without difficulty. The second reason, perhaps the most important one, is that Brazilian soil is very rich in variety of silicate crystals, several of them commercially and, in many instances, industrially importants.They have, on the other hand, many interesting physical properties to be investigated. [...] The third reason is what will be seen in this Project, namely, as quartz suddenly became a mineral of exceptionally importance in industry as a consequence of series of investigation of its physical properties, it is expected here to detect through systematic and cumulative laboratory studies of available natural silicate crystals some properties that lead us to an important practical application. The present Project intends to investigate systematically physical properties of available natural Brazilian silicate crystals, starting with optical absorption, luminescence and magnetic resonance properties. (AU)