Photochromism of a BaMgSiO₄ Phase Prepared with a Nonstoichiometric Nominal Composition

Abstract

Barium magnesium silicate, BaMgSiO 4 , sintered together with H 3 BO 3 in a reducing atmosphere is known to show photochromism, with the generation of a pink color following UV irradiation. It is thought that this photochromism originates from oxygen vacancies in the silicate. In this work, we investigated the nominal Ba-deficient composition Ba 1-x MgSiO 4-x (0 < x < 0.05) in an attempt to effectively generate oxygen vacancies in the silicate. BaMgSiO 4 phases were obtained from a combination of BaCO 3 , MgO and SiO 2 , without the addition of H 3 BO 3 , by sintering in a reducing atmosphere. All samples were pink-colored after UV irradiation and this photochromism was confirmed to be an intrinsic property of BaMgSiO 4 . The color densities of our samples were inferior to that of a previously reported sample sintered with the addition of H 3 BO 3 , and the addition of H 3 BO 3 is believed to improve the photochromism color density. A tendency for the color density to decrease with increasing Ba-deficiency was found among our samples. The observed degradation of the photochromism is discussed based on nonstoichiometry in the BaMgSiO 4 phase.