Optical Properties of Various Strontium Bismuthates: Luminescence and UV‐induced Photocoloration

Abstract

The low-temperature photoluminescence (T < 300 K) and UVinduced formation of color centers of recently synthesized Sr 2 Bi 2 O 5 , Sr 3 Bi 2 O 6 and Sr 6 Bi 2 O 11 bismuthates are examined. The estimated Mott-Seitz activation energies, ranging from 88 to 167 meV, correspond to various emission bands. Comparison of the response of all three bismuthates when exposed to UVillumination indicates that photoluminescence and formation of color centers are two processes that compete with photocatalytic activity. The most photoactive Sr 6 Bi 2 O 11 bismuthate exhibits neither luminescence nor the ability toward photocoloration. By contrast, Sr 2 Bi 2 O 5 , which exhibits no photocatalytic activity, displays an intense photoluminescence; UV irradiation causes significant changes of its color. The bismuthate Sr 3 Bi 2 O 6 occupies an intermediate position as it exhibits some photocatalytic activity, as well as the ability to photoluminesce and to undergo photocoloration. Simple models are described to systematize the experimental results, which place these bismuthates into a new class of photoactive materials.

Influence of the Type and Concentration of the Dopant on the Photocatalytic Activity of Strontium Bismuthate Sr₂Bi₂O₅

“…To obtain both pure and doped samples of strontium bismuthate Sr2Bi2O5, solid-phase synthesis was used, which had shown its efficiency earlier [26,27]. Strontium nitrate tetrahydrate (Sr(NO3)2*4H2O) and oxides of bismuth (Bi2O3), cerium, yttrium and lanthanum were used as precursors.…”

“…The aim of this work is to establish the degree of influence of the type and concentration of the dopant on the optical and photocatalytic properties of alkaline earth metal bismuthate using the example of strontium bismuthate Sr2Bi2O5. The choice of this strontium bismuthate is due to the fact that the photocatalytic and optical properties of this strontium bismuthate have been studied in detail by a number of scientific groups [16,[20][21][22]26,27]; it is easy to obtain and has a high tolerance to defects, which makes it possible to introduce dopants into it without significant deformations of the crystal lattice and maintaining its phase homogeneity [26].…”