Three types of photo-luminescence in natural zircon.

Abstract

Three types of luminescence spectra of natural zircon can be clearly distinguished: (1) type I that consists of line spectra is due to the transition within 4f electrons of REE such as Dy3+, Eu3+ Sm3+ and Tm3+, (2) type II with broad bands is originated from radiation centers due to alphadecay of U and Th, whose band intensities are closely related to the geologic age of the formation of zircon, and (3) type III is mainly formed by the activators of U and P in the zircon, where P acts as a sensitizer. The activators of Mn, Ni and V with the transition of 3d-3d electrons, and the activators of Ca, Zn, Ba, Sc and P with electron-hole centers also may contribute to the formation of the type III luminescence. Natural zircons have usually the type II luminescence with varying proportions of the type I or the type III luminescences. Natural zircon gives complex absorption spectra related to the type II luminescence. To characterize natural zircons, the latter luminescence spectra can be sensitively and easily detectable rather than the absorption spectra Also, the type II spectra show remarkable extinctionrestoration phenomena by the heat-treatment, and show the displacement of those band positions as the crystallographic direction changes (pleochroism of the luminescence). Color and luminescence of natural zircon are mainly caused by these luminescent centers identical to color centers.