Sintering-driven effects on the band gap of (Pb,La)(Ti,Ni)O-3 photovoltaic ceramics

Author(s)

Vargas, Natalia F. C. ^[1] ; Alkathy, Mahmoud S. ^[2] ; Eiras, Jose A. ^[2] ; Mastelaro, Valmor Roberto ^[3] ; Lente, Manuel H. ^[1]

Affiliation

^[1] Univ Fed Sao Paulo, Inst Ciencia & Tecnol, BR-12231280 Sao Jose Dos Campos, SP - Brazil

^[2] Univ Fed Sao Carlos, Dept Fis, Sao Carlos - Brazil

^[3] Univ Sao Paulo, Inst Fis Sao Carlos, Sao Carlos - Brazil

• Document type: Journal article
• Source: Journal of the American Ceramic Society; v. 104, n. 6 JAN 2021.
• Web of Science Citations: 0

Abstract

In this work, the influence of the sintering temperature on the physical properties of (Pb0.8La0.2)(Ti0.9Ni0.1)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 degrees C to 1250 degrees C. It is demonstrated that the simple substitution of Ti4+ by Ni2+ 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 (VO2-) amount. It is believed that the impact of the creation of these thermally induced VO2- is manifold. The presence of VO2- and Ni2+ ions generate the Ni2+-VO2- 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 Ni2+-VO2- defects also changed the local symmetry of Ni2+ ions from octahedral to a square pyramid, thus lifting the degeneracy of the Ni2+ 3d orbitals. With the increase in the sintering temperature, lower-energy absorbing intraband states were also formed due to an excess of VO2-, 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. (AU)

• FAPESP's process: 19/03110-8 - Synthesis and photovoltaic characterization of thin films based on ferroelectric and multiferroic perovskite for solar cells application
• Grantee: Mahmoud Saleh Mohammed Alkathy
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• FAPESP's process: 17/13769-1 - Multiferroic and ferroelectric materials for energy converters: synthesis, properties, phenomenology and applications
• Grantee: José Antonio Eiras
• Support Opportunities: Research Projects - Thematic Grants