Effect of cellulose derivatives on the morphology, agglomeration, and phase transformation of spinel nanoparticles prepared via modified sol-gel method and comparison of optical transmission of spark plasma sintered ceramic

The Pechini method is one of the alkoxide sol-gel methods in which citric acid (CA) and ethylene glycol (EG) pair are used for gel preparation. The major downside of this method is an agglomeration of the produced nanoparticles. In this research, by substituting ethylene glycol chelating agent with cellulose derivatives (such as carboxy methyl cellulose (CMC) and hydroxy propyl methyl cellulose (HPMC), the reduction of the extent of spinel nanoparticle agglomeration is examined. To this aim, a different ratio of CMC and HPMC to metal ions (Mg2+ and Al3+) was used. The results indicated that the sample synthesized with 1 g CMC had the minimum agglomeration and particle size (50 nm). Next, this sample was consolidated through the spark plasma sintering method at 1500 °C for 15 min. The microstructure, grain size and optical transmittance of the SPSed body were compared with the sample prepared with the conventional Pechni method. The results showed that the maximum visible light and infrared transmission of the bulk prepared from the modified Pechini method was greater than that of the sample prepared via the conventional Pechini method. The optimal visible light transmission was 85%, and in the IR region at a wavelength of 5 µm was 75%. This is related to the higher apparent density of this ceramic (99.98% vs 98.82%) and the lower porosity of this sample.