Avaliação das características termoelétricas e termorresistivas da matriz semicondutora de óxido de zinco dopado com manganês em diferentes concentrações

Abstract

In the current context, scientific and technological development is fundamental to the needs of a modern society, such as information capacity, data speed, energy autonomy, miniaturization of components and equipment, lower production costs, and more efficient systems. In this vision and reality, the world of semiconductor materials plays a fundamental, even essential, role. Therefore, the study of these materials will always have a scientific and technological appeal that attracts the attention of those who conduct research. When dealing with sensing systems and the production of electrical energy, it is something that sparks interest in the results that will be generated. Therefore, in this work we used the zinc oxide (ZnO) semiconductor matrix, which has a wide band gap of ≈ 3,37 eV, so that through the doping process we could evaluate the effect on the thermoresistive and thermoelectric response of this matrix doped with the transition metal manganese (Mn), at concentrations of x = 0,1; 0,2; 0,3; 0,4 and 0,5 mol of Mn+2, in the Zn+2 substitution process, in the Zn1-xMnxO system, using the combustion reaction synthesis route for the production of the systems. The produced systems were calcined, beneficiated, pressed, and sintered at a temperature of 1100 °C at a rate of 10 °C/min. After preparation, their microstructure was analyzed using X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) with EDS, band gap analysis using Ultraviolet Spectroscopy (UV-Vis), and thermoresistive and thermoelectric responses. The results showed the formation of a second phase, with a dense material whose average particle size increased with increasing Mn+2 concentration. Considering a theoretical value of 3,37 eV for pure ZnO, the band gap width was affected by the addition of the dopant, with the highest value obtained being 2,91 eV for x = 0,3 mol of Mn+2 and the lowest value found being 2,72 eV for x = 0,5 mol, but preserving the semiconductor characteristic even with doping. In the thermoresistive results, a thermistor with a negative thermal coefficient (NTC) was produced, where the minimum β found was at x = 0,1 mol of Mn+2 with 4334K for the 75°C to 100°C test, and the best for x = 0,2 mol Mn+2 resulting in 6396K in the 50°C – 100°C test. Therefore, the results obtained proved satisfactory for this initial study, where we were able to produce high-quality NTC thermistors, reinforced by the ln(ρ) x 1000/T(K) graph, which also demonstrated specific temperature ranges within those analyzed, in which β exceeded commercial values. In the thermoelectric results, we obtained values between -835.53 μV/°C and -57.62 μV/°C and -72.02 μV/°C to - 1.02 μV/°C for pure ZnO doped with 0.5 mol of Mn at temperatures of 50°C and 100°C, respectively.