Blue afterglow of undoped CaAl₂O₄ nanocrystals

School of Mathematics and Physics, Changzhou University - Jiangsu 213164, China

^(a) dongshanisland@126.com

Received: 1 March 2019
Accepted: 10 July 2019

Abstract

This paper reports on the intense blue afterglow from undoped CaAl₂O₄ nanocrystals in an attempt to achieve a clear understanding of the afterglow mechanism of Eu²⁺-doped CaAl₂O₄. Undoped CaAl₂O₄ nanocrystals were obtained via solution combustion technique. Intense blue afterglow, which is quite similar to that of Eu²⁺-doped CaAl₂O₄, is observed with naked eyes for undoped CaAl₂O₄ regardless of no Eu²⁺ species in the phosphors. Based on density functional calculations, the electronic structures of oxygen-deficient CaAl₂O₄ are given, and the mechanism of the blue afterglow from undoped CaAl₂O₄ is discussed in terms of the oxygen vacancy introduced midgaps. The recorded blue afterglow from undoped CaAl₂O₄ nanocrystals leads to significant progress in our fundamental understanding of the afterglow mechanisms of Eu²⁺-doped CaAl₂O₄.