Paramagnetic electron centers in BaTiO3 nanoparticle powders. Issue 22 (1st June 2021)

• Record Type: Journal Article
• Authors: Neige, Ellie; Diwald, Oliver
• Is Part Of: Physical chemistry chemical physics. Volume 23:Issue 22(2021)
• Page Start: 12881
• Page End: 12888
• Publication Date: 2021-06-01
• Subjects: Chemistry, Physical and theoretical -- Periodicals; 541.3
• DOI: 10.1039/d1cp01128f
• Languages: English
• ISSNs: 1463-9076

Abstract

Abstract : Paramagnetic point defects in BaTiO3 nanoparticles. Abstract : Knowledge about the emergence and depletion of point defects in BaTiO3 (BTO) nano-structures during materials processing is key to our understanding of their later activity as components in functional dielectric devices or as photocatalysts. In this electron paramagnetic resonance (EPR) study we investigated BaTiO3 nanoparticle powders produced by flame spray pyrolysis (FSP) with powders of TiO2 anatase nanocrystals of comparable size as reference system. Paramagnetic Ti 3+ ions located at regular lattice sites and with well-defined EPR signatures were measured in vacuum annealed BaTiO3 nanoparticles, which convert upon further annealing in the temperature range between 873 K and 1173 K from monocrystalline grains with an average size of d = 12 nm, BTO (873 K), to polycrystalline particles with d = 70 nm, BTO (1173 K). Whereas the starting material hosts predominantly polaron-type Ti 3+ ions being surrounded by compressed O 2− ion octahedra, barium–oxygen divacancy complexes, , become susceptible to electron trapping in polycrystalline and tetragonal BTO (1173 K) particles after pre-annealing at temperatures T > 873 K. The insights obtained provide a base for the detection of local distortion effects, for the identification of charge trapping sites and for the elucidation of their impact on spontaneous polarization in BaTiO3 nanoparticles as photocatalysts or dielectric components.