Non-Isothermal Kinetics of Coats-Red Fern in the Critical Points: Formation of Al2-xCrxO3 (x = 0.02) powders obtained by Sol-Gel Method

In this study, ruby (Cr3+ doped Al2O3) was synthesized through the citrate method employing citric acid in excess as a chelating and fuel agent. The primary focus of our study was on two critical phase heat points, TPH, and TPD. The system was considered opaque, and we aimed to comprehend the behavior of crystal structure formation. Thermal kinetics was examined using the Coates-Redfern method, and various mechanisms were selected based on heating coefficients. Twenty-eight models were explored, combining the kinetics approach with experimental thermal analyses, including Thermogravimetry (TGA) and Differential Scanning Calorimetry (DSC). Kinematic parameters thanks to model fitting methods, were confirmed with a high R-squared coefficient of between (0.95 - 0.99) . Despite slight differences and notable activation energy with reaction order, nucleation and subsequent random nucleation and diffusion mechanisms were revealed. Heat treatment showed consistency in Fourier transform infrared (FTIR) separation of the complex on aluminum and chromium oxides, indicating the presence of homo-bond decay upon treatment at 200-500-1000 °C. After the decomposition of the organic matter, the ceramic transforms into a green powder and subsequently transitions to a vividly crystalline pink color at a specific temperature of 1100 °C. All the surprising values found provide insight into the complexity of the crystallization process. It crystallizes in the hexagonal system in space group R-3c, according to analytical data from X-ray diffraction (XRD), however semi-investigation revealed that its morphological state is arbitrarily formed and ranges from 0.5 to 78 µm. Additionally, an elemental analysis study (EDS) verified the presence of Cr and O in the sample series