Thermométrie, thermomètre primaire et applications phosphores à base de vanadate de terre rare
- Autores: Nesrine Mohamed Bhiri
- Directores de la Tesis: Joan J. Carvajal (dir. tes.), Mohamed Dammak (codir. tes.), M. Cinta Pujol Baiges (codir. tes.)
- Lectura: En la Universitat Rovira i Virgili ( España ) en 2020
- Idioma: español
- Tribunal Calificador de la Tesis: Wahiba Boujelbene (presid.), Patricia Haro Gonzalez (secret.), Mohamed Koubaa (voc.)
- Programa de doctorado: Programa de Doctorado en Nanociencia, Materiales e Ingeniería Química por la Universidad Rovira i Virgili
- Materias:
- Enlaces
- Tesis en acceso abierto en: TDX
- Resumen
The work carried out in this thesis aims to overcome some issues that are imposed on current temperature detection and lighting devices. Then, in this thesis we paid an attention to the parameters that can affect the thermometric and the luminescence performances of the vanadate rare earth matrix. We have synthesized a several compounds of Y/GdVO4 MCs that can be mono-doped Er or Eu, co-doped Er-Yb and tri-doped Er-Eu-Yb MCs through a high temperature solid-state reaction method. Their structural and morphological characteristics have been studied in detail. They shows that all the vanadate matrix synthesized crystallize well in the tetragonal phase with the I41/amd space group. The ESEM analysis shows that all the samples are composed of a micron grains that are irregular agglomerated quasi-elliptic like crystals with smooth surfaces.
For the thermometric applications, the different performance of the luminescent thermometers Er:GdVO4 and Er-Yb:GdVO4 in terms of thermal sensitivities and temperature uncertainties when operated under conditions of Down and Up-conversion were studied and compared, in the non-saturation regime, using the self-referenced fluorescence intensity ratio technique. This work illustrate that with exciting in the NIR, a thermal effect can be generated and then can affected the thermometric performances of the detection systems. The sensor with the highest thermal relative sensitivity under Up-conversion process have been explored to be used as a primary thermometer. Then, a primary calibration of the 1 at.% Er3+, 20 at.% Yb3+: GdVO4 microcrystals as luminescent thermometer based on the known equation of state of Boltzmann distribution of the electronic population of the two Erbium emitting coupled levels has been given. Besides, the effect of the excitation power on the thermometric parameter, the relative thermal sensitivity and the temperature resolution has been also analyzed. It shows that it is better to work at so lower pump power in order to avoid as much as possible the extra-heating of the sample generated by the excitation and which can reduce the performance of the detection systems. We have demonstrated well how the population of the emitter levels can be affected by this excitation pump power since it causes a competition between the process of the thermalization and the non radiative processes. Later, we have studied the thermometric performances for the Er-Yb:YuGdwVO4 and we have compared them for two different excitation laser power situated in the non-saturation regime. It is well highlighted that the heating generated by the excitation laser can hardly affect the energy gap between the thermal coupled levels and then the thermometric performances. Finally, we have focussed on the determination of the ET process that can be responsible for the lighting of the Er-Eu-Yb:GdVO4 and we have determined the CIE chromaticity of all the synthesized samples with different concentrations of Eu ions. This study reveals, with exciting in the UV the samples can exhibit a red or a green light, while with exciting in the NIR the samples can exhibit a yellow light.
