Magnesium aluminate spinel (MgAl2O4¬) is an excellent optical ceramic with high transparency (87 percent), which has received considerable attention in the last decade. Still, despite more than a century of discovering this ceramic compound, in order to achieve the desired industrial transparency, extensive research on it's underway. Many methods have been used to synthesis of magnesium aluminate spinel in studies. Also, many additives have been used to reduce the formation temperature and improve the magnesium aluminate spinel sintering behavior, among which the addition of lithium fluoride had the greatest effect on transparency. In this study, in order to improve the distribution of lithium fluoride as an additive, LiF nanoparticles were first synthesized by two methods such as co-precipitation and sol-gel route in different conditions including Li+ ion concentration in solution and calcination temperature. According to the results, the sol-gel method provided better results and was selected to continue the research. In this method, LiF nanoparticles with an average particle size of about 146 nm were obtained using a concentration of 1M and a calcination temperature of 400 °C. Further, magnesium aluminate spinel nanoparticles were synthesized by sol-gel method. According to the results of the TG-DSC thermal analysis, calcination temperature was chosen between 600 to 1000 °C and the powders were calcined. Using XRD results and scanning electron microscopy images, the average size of crystallites and the mean particle size were about 6.9 and 50 nm respectively, with a specific area of 53 m2/gr. Using optimal conditions, LiF nanoparticles were synthesized and calcined simultaneously in the spinel gel and then sintered with SPS at 1400 °C and pressure of 80 MPa. Additionally, the spinel powder without additive was sintered to compare the results. On the other hand, LiF nanoparticles were synthesized again on the same basis on a mixture of aluminum oxide nanoparticles and magnesium oxide powders and then sintered to similar conditions, and the transparent bulk spinel with a relative density of 99% was obtained. Also, in order to compare the microstructural and optical results of the components, the alumina and magnesia non-additive mixed powder, and once again with 1 Wt% LiF admixture in a common method was SPSed to investigate the effect of homogeneity of the additive. XRD results showed that a transparent sample of single-phase magnesium aluminate spinel is possible using a mixture of non-calcined oxide powders, with and without an additive. The infrared transmittance for a bulk spinel, that sintered without the addition of a spinel powder, and a mixture of alumina and magnesia powder, 39 and 58 percent were measured respectively, and these values increased by 58 and 65 percent, respectively, by modifying the microstructure and reducing porosity because of adding 1Wt% of LiF to the powders prior to the sintering. Whiles, samples sintered from powders which are LiF additive in situ synthesized onto them, were 65% and 78%, respectively, due to increased transparency regarding the homogeneity of the microstructure of the samples, the reduction of porosity and removal carbon. Thus, the microstructure results of optical components showed that by adding 1Wt% LiF to on-site oxide powders before sintering, transparency in Infrared area increased by 13% compared to the usual LiF mixing method. Keywords: MgAl2O4, LiF, Sol-Gel method, Spark plasma sintering, Microstructure, Optical properties