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Sintering‐driven effects on the band gap of (Pb,La)(Ti,Ni)O 3 photovoltaic ceramics
Author(s) -
Vargas Natália F. C.,
Alkathy Mahmoud S.,
Eiras José A.,
Mastelaro Valmor Roberto,
Lente Manuel H.
Publication year - 2021
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/jace.17682
Subject(s) - sintering , materials science , band gap , absorption edge , absorption band , ceramic , ion , analytical chemistry (journal) , mineralogy , metallurgy , optics , optoelectronics , chemistry , organic chemistry , chromatography , physics
In this work, the influence of the sintering temperature on the physical properties of (Pb 0.8 La 0.2 )(Ti 0.9 Ni 0.1 )O 3 (PLT‐Ni) ceramics is reported. The experimental data revealed that the energy band gap of PLT‐Ni ceramics could be tailored from approximately 2.7 to 2.0 eV by changing the sintering temperature from 1100°C to 1250°C. It is demonstrated that the simple substitution of Ti 4+ by Ni 2+ cations is effective to decrease the intrinsic band gap while increasing the tetragonality factor and the spontaneous polarization. However, the additional red‐shift observed in the absorption edge of the PLT‐Ni with increasing the sintering temperature was associated with a continuous increase in the oxygen vacancies ( V O 2 ‐ ) amount. It is believed that the impact of the creation of these thermally induced V O 2 ‐is manifold. The presence of V O 2 ‐and Ni 2+ ions generate the Ni 2+ ‐ V O 2 ‐defect‐pairs that promoted both a decrease in the intrinsic band gap and an additional increase of the tetragonality factor, consequently, increasing the spontaneous polarization. The creation of Ni 2+ ‐ V O 2 ‐defects also changed the local symmetry of Ni 2+ ions from octahedral to a square pyramid, thus lifting the degeneracy of the Ni 2+ 3 d orbitals. With the increase in the sintering temperature, lower‐energy absorbing intraband states were also formed due to an excess of V O 2 ‐ , being responsible for an add‐on shoulder in the absorption edge, extending the light absorption curve to longer wavelengths and leading to an additional absorption in “all investigated” spectrum as well.