Banca de DEFESA: RAPHAEL ANACLETO MARTINS PIRES DE OLIVEIRA

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : RAPHAEL ANACLETO MARTINS PIRES DE OLIVEIRA
Date: 02/12/2025
TIME: 14:00
LOCAL: Remota - https://conferenciaweb.rnp.br/conference/rooms/defesa-doutorado-ppgnano-raphael-anacleto/invite?institution_slug=ufabc&show-suggestion=false
TITLE:

Effects of La Content on Ceria-Lanthana Thin Films prepared by Pulsed Laser Deposition

PAGES: 168
BIG AREA: Engenharias
AREA: Engenharia de Materiais e Metalúrgica
SUBÁREA: Materiais Não-Metálicos
SPECIALTY: Cerâmicos
SUMMARY:

Lanthanum-doped ceria (LDC) thin films were grown by pulsed-laser deposition on Si(100), amorphous quartz, and SrTiO₃ (100) aim to tune oxygen-vacancy chemistry and transport. Structure and surfaces were examined by XRD, AFM/SEM, UV-Raman, and XPS; electrochemical properties were measured using EIS in controlled atmospheres. UV-Raman observed the fluorite F₂g red-shift and broadening, along with the vacancy-activated D₁/D₂ envelope, which are typical markers of non-stoichiometry in ceria, while XPS quantified Ce³⁺/Ce⁴⁺ ratios and O 1s speciation [1], [2]. On Si(100) (10⁻¹ mbar), films showed strong (200) texture at x≈0.10–0.20 with increasing defect signatures; higher x caused defect clustering and surface roughening. On quartz (10⁻² mbar), La and lower pO₂ levels increased reducibility and mixed conduction in H₂, consistent with vacancy formation and small-polaron formation [3], [4]. Epitaxial LDC10 on SrTiO₃ (100) (10⁻³ mbar) displayed a softened, broadened F₂g band and an O 1s spectrum dominated by lattice oxygen with minimal hydroxylation, indicating a chemically clean, vacancy-stabilised surface. In air, it showed a single semicircle with Eₐ ≈ 0.29 eV and a conductivity of ~10⁻² S cm⁻¹ at 600 °C; in H₂, the conductivity increased by 1–2 orders of magnitude, with Eₐ ≈ 0.5–0.6 eV, reflecting mixed ionic–electronic conduction in reduced ceria. Electronic conduction is well described by small-polaron hopping between Ce³⁺/Ce⁴⁺ centres, while oxygen-vacancy migration determines the ionic activation barrier [5], [6]. Optimal performance is achieved near 10 mol% La, where vacancy creation is high but clustering remains limited; higher doping levels impair transport due to dopant–vacancy association and short-range ordering [7]. These findings connect growth conditions, defect chemistry, and charge transport, guiding substrate and atmosphere choices for low-temperature SOFC and mixed-conducting oxide devices.

COMMITTEE MEMBERS:
Presidente - Interno ao Programa - 1552290 - ANDRE SANTAROSA FERLAUTO
Membro Titular - Examinador(a) Interno ao Programa - 1545738 - MARCIA TSUYAMA ESCOTE
Membro Titular - Examinador(a) Externo à Instituição - VICTOR BURATTO TINTI - DTU
Membro Titular - Examinador(a) Externo à Instituição - EVERTON BONTURIM - UPM
Membro Titular - Examinador(a) Externo à Instituição - FÁBIO CORAL FONSECA - IPEN
Membro Suplente - Examinador(a) Interno ao Programa - 1545089 - DANIEL ZANETTI DE FLORIO
Membro Suplente - Examinador(a) Externo ao Programa - 3472684 - DIEGO EDISON LOPEZ SILVA
Membro Suplente - Examinador(a) Externo à Instituição - ANDRE LUIS DA SILVA