Abstract
In ceramic industry, zircon sand is widely used in different applications because zirconia plays a role as common opacifying constituent. In particular, it is used as a basic component of glazes applied to ceramic tiles and sanitary ware as well as an opacifier in unglazed bulk porcelain stoneware. Natural zircon sands are the major source of zirconium minerals for industrial applications. In this paper, long, medium, and short range studies were conducted on zirconium minerals originated from Australia, South Africa, and United States of America using conventional and less conventional techniques (i.e., X-Ray Diffraction (XRD), Positron Annihilation Lifetime Spectroscopy (PALS), and Perturbed Angular Correlations (PAC)) in order to reveal the type and the extension of the regions that constitute the metamict state of zircon sands and the modifications therein produced as a consequence of the industrial milling process and the thermal treatment in the production line. Additionally, HPGe gamma-ray spectroscopy confirms the occurrence of significant levels of natural radioactivity responsible for metamictization in the investigated zircon samples. Results from XRD, PALS, and PAC analysis confirm that the metamict state of zircon is a dispersion of submicron disordered domains in a crystalline matrix of zircon.
Highlights
Zirconium is the 18th most abundant element on Earth
Long, medium, and short range studies were conducted on zirconium minerals originated from Australia, South Africa, and United States of America using conventional and less conventional techniques (i.e., X-Ray Diffraction (XRD), Positron Annihilation Lifetime Spectroscopy (PALS), and Perturbed Angular Correlations (PAC)) in order to reveal the type and the extension of the regions that constitute the metamict state of zircon sands and the modifications therein produced as a consequence of the industrial milling process and the thermal treatment in the production line
The samples studied in the present work are natural zircons from the United States, Australia, and South Africa in two different stages of their industrial elaboration: sands were named according to their origin as USA, AUS, and SUD, respectively, and sands micronized at a size of D50 = 4 μm were named as USA4, AUS4, and SUD4
Summary
Zirconium is the 18th most abundant element on Earth In nature it mainly occurs as the free oxide ZrO2 (baddeleyite), but more commonly as zircon (ZrSiO4). The common name for zircon in connection with its most typical ore, are mainly exploited in the refractory and ceramic industries. The former application originates from zircon excellent thermophysical properties such as the low coefficient of thermal expansion, low electrical and thermal conductivity, and good corrosion resistance [1]. The use of micronized zircon and zircon flour in ceramic products has been forecast to reach the 56% in 2012 of the total worldwide industrial consumption. Australia (the main producer), together with South Africa, United States, and India, accounts for over 80% of the global zircon production [3]
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