Room-temperature photoluminescence ofBaTiO3: Joint experimental and theoretical study

Abstract

Strong photoluminescent emission has been measured at room temperature for noncrystalline BaTiO 3 ͑BT͒ perovskite powders. A joint experimental and theoretical study has been carried out to rationalize this phenomenon. From the experimental side, BT powder samples have been synthesized following a soft chemical processing, their crystal structure has been confirmed by x-ray data and the corresponding photoluminescence ͑PL͒ properties have been measured. Only the structurally disordered samples present PL at room temperature. From the theoretical side, first-principles quantum-mechanical techniques, based on density-functional theory at the B3LYP level, have been employed to study the electronic structure of crystalline ͑BT-c͒ and asymmetric ͑BT-a͒ models. Theoretical and experimental results are found to be consistent and their confrontation leads to an interpretation of the PL apparition at room temperature in the structurally disordered powders.

Structural conditions that leads to photoluminescence emission in SrTiO3: An experimental and theoretical approach

“…This explanation of vector displacement takes into account previous work on the perovskite structure. 23,24 Recently, Lazaro et al 51 reported results of a pre-edge feature of Ti and Ca K-edge XANES in a disordered CaTiO 3 perovskitelike structure. Their findings indicated two types of environments for the calcium, namely, 11-fold and 12-fold calcium coordinations.…”

“…[22][23][24] This emission was attributed to localized levels above the valence band ͑VB͒ and below the conduction band ͑CB͒. Moreover, a charge transfer occurred from the ͓TiO 6 ͔ cluster to the ͓TiO 5 ͔ cluster in the disordered system.…”

“…Moreover, a charge transfer occurred from the ͓TiO 6 ͔ cluster to the ͓TiO 5 ͔ cluster in the disordered system. [23][24][25][26] After further advances in studies of the electronic transitions that display PL emission, Kan et al 27 concluded that oxygen deficiency in Ar + -irradiated ST is the only cause for blue-light PL emission at room temperature. However, several reports in the literature explain the favorable conditions for PL emission in materials presenting a degree of order-disorder.…”

Highly intense violet-blue light emission at room temperature in structurally disordered SrZrO3 powders

“…15 First principle calculations revealed that this disordered structure leads to local polarization and a charge gradient in the structure. 9 We believe that the same mechanism takes place in structurally disordered SZ powders.…”

“…7 As can be seen, there is no general consensus in the literature to explain why and how radiative decay takes place in perovskitelike structures with a certain degree of disorder. Our group demonstrated that a series of structurally disordered titanates ͑ATiO 3 , where A = Ca, Sr, and Ba͒ displays intense photoluminescence at room temperature when excited by a 488 nm laser excitation line, [8][9][10] and that more intense PL emission is obtained with a certain structural order-disorder in the material.…”