Banca de QUALIFICAÇÃO: KARLA KARINY FERREIRA BARBOSA

Uma banca de QUALIFICAÇÃO de DOUTORADO foi cadastrada pelo programa.
STUDENT : KARLA KARINY FERREIRA BARBOSA
DATE: 05/12/2022
TIME: 10:00
LOCAL: Auditório 8º andar, bloco B
TITLE:

"Green-chemistry" synthesis of the lead-free Cs 2 AgSbCl 6 double perovskite by the mechanochemical method

PAGES: 50
BIG AREA: Ciências Exatas e da Terra
AREA: Física
SUBÁREA: Física da Matéria Condensada
SPECIALTY: Estrutura de Líquidos e Sólidos; Cristalografia
SUMMARY:

Despite the rapid development and enormous success of organic-inorganic hybrid halide perovskites (ABX₃), such as CH₃NH₃PbI₃ as absorbers for perovskite-based solar cells (PSCs), the commercial applications of photovoltaic techniques still face several challenges, like decomposition when exposed to light and moisture, and lead toxicity. On the other hand, the double perovskites (A₂B’B”X₆) are derived from the AB”X₃ when half of the octahedrally coordinated B’-cations are partially replaced by the suitable B”-cations. They are attracting attention due to a new design strategy to replace Pb²⁺ ions with the coupling of a monovalent M⁺ ion and a trivalent M³⁺ ion, leading to a new family of quaternary double perovskites. In this context, we aim to synthesize and characterize Cs₂Ag_1−xSbCl 6 (x = 0, 1, 2, 4 %wt) powdered samples designed for solar cell applications and magnetic properties. The samples were synthesized in a mixer mill MM 400 using an Eppendorf ○ R as a vessel with 5 mm balls and 15−, 45−, and 60−minute mixer time. The crystalline phase and morphological features were investigated by X-ray powder diffraction (XRPD). The evolution of the sample structure as a function of the mixer time was obtained by X-ray powder diffraction at room temperature. Below 20 minutes of mixing time, the samples contain a mixture of a cubic AgCl-phase, the 2D-perovskite Cs₃Sb₂Cl₉, and the double perovskite Cs₂AgSbCl₆. As the mixer time increases, the concentration of AgCl and the Cs₃Sb₂Cl₉ decreases until the complete formation of the primary phase. The double perovskite Cs₂AgSbCl₆ phase crystallized in a cubic crystal system with space group  (No. 225), presenting two non-equivalent crystallographic sites for the Ag and Sb atoms. The Mn-doped samples crystallized with the same cubic structure, and Rietveld refinement reveals the occupation of the Mn²⁺ at the Ag sites. These results showed that this synthesis method proved efficient in obtaining polycrystalline-Cs₂Ag_1−xMn_xCl₆ (x = 0, 1, 2, 4 %wt) samples. Continuing this work, the structural and magnetic properties will be investigated by temperature-dependent magnetization measurements.

BANKING MEMBERS:
Presidente - Interno ao Programa - 2605463 - JOSE ANTONIO SOUZA
Membro Titular - Examinador(a) Interno ao Programa - 1544408 - GUSTAVO MARTINI DALPIAN
Membro Titular - Examinador(a) Externo ao Programa - 1671688 - ANDRE SARTO POLO
Membro Suplente - Examinador(a) Interno ao Programa - 1760527 - FLAVIO LEANDRO DE SOUZA
Membro Suplente - Examinador(a) Interno ao Programa - 2249395 - THIAGO BRANQUINHO DE QUEIROZ
Membro Suplente - Examinador(a) Externo ao Programa - 2218228 - LUANA SUCUPIRA PEDROZA
Membro Suplente - Examinador(a) Externo ao Programa - 1545738 - MARCIA TSUYAMA ESCOTE
Membro Suplente - Examinador(a) Externo ao Programa - 1544394 - PAULA HOMEM DE MELLO