Banca de DEFESA: ANDERSON DE AZEVEDO GOMES SANTIAGO

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : ANDERSON DE AZEVEDO GOMES SANTIAGO
DATE: 20/05/2022
TIME: 09:00
LOCAL: Plataforma google meet
TITLE:

Study of the photoluminescent properties of Mg1-xSrxMoO4 and Zn1-yCayWO4 heterostructures obtained by the ultrasonic spray pyrolysis method

KEY WORDS:

Molybdate; Tungstate, Ultrasonic spray pyrolysis; Photoluminescence.

PAGES: 109
BIG AREA: Engenharias
AREA: Engenharia de Materiais e Metalúrgica
SUBÁREA: Materiais Não-Metálicos
SPECIALTY: Cerâmicos
SUMMARY:

Molybdates and tungstates are inorganic materials with immense potential in application as white light-emitting diodes (wLEDs), which are an alternative to traditional lighting sources. In this study, the synthesis and characterization of the composite MgMoO₄:SrMoO₄ (with molar ratios of 1:0; 0.75:0.25; 0.5:0.5; 0.25:0.75 and 0:1) and ZnWO₄:CaWO₄ (with molar ratios of 1:0; 0.8:0.2; 0.6:0.4; 0.4:0.6; 0.2:0.8 and 0:1), prepared by the ultrasonic spray pyrolysis method and their photoluminescent properties were investigated. Using X-ray diffraction, for the composite MgMoO₄:SrMoO₄, the monoclinic β-MgMoO₄ phase was observed at a molar ratio of 1:0 and the tetragonal scheelite phase of SrMoO₄ at a molar ratio of 0:1. However, for the composite ZnWO₄:CaWO₄, the monoclinic phase ZnWO₄ was obtained at a molar ratio of 1:0 and the scheelite-type tetragonal phase of CaWO₄ when the molar ratio was 0:1. The formation of a particulate material composed of both phases was observed for the intermediate molar ratios. Scanning electron microscopy images showed that MgMoO₄:SrMoO₄ and ZnWO₄:CaWO₄ particles show a spherical morphology formed by primary nanoparticles. Raman scattering spectroscopy allowed the precise identification of Raman modes for different compositions and their assignment to SrMoO₄ or β-MgMoO₄ modes. Bandgap energies were found in a range between 4.2 eV and 4.4 eV for the MgMoO₄:SrMoO₄ composites and between 3.8 eV and 4.0 eV for ZnWO₄:CaWO₄, influenced by the order/disorder structural degree of the materials. The photoluminescence emission spectra of the particles showed neutral- and cool-white emission with high quality white light (CRI>80%). The MgMoO₄:SrMoO₄ samples synthesized with a molar ratio of 1:0, 0.25:0.75 and 0.5:0.5 formed materials with potential for application in LED lamps (6,500 K) and pure white light sources (5,500 K) while the samples of ZnWO₄:CaWO₄ can be considered as promising white light sources, mainly for the sample with molar ratio 0.2:0.8, for application in LED lamps (6,500 K).

BANKING MEMBERS:
Presidente - 1883170 - MAURICIO ROBERTO BOMIO DELMONTE
Interna - 1802888 - FABIANA VILLELA DA MOTTA
Externo ao Programa - 2941160 - JOSE HERIBERTO OLIVEIRA DO NASCIMENTO
Externa à Instituição - SAYONARA ANDRADE ELIZIÁRIO - UFPB
Externo à Instituição - NEFTALÍ LENIN VILLARREAL CARREÑO - UFPel