## 1 Introduction  
Ilmenite with a composition of FeO.TiO\({}_{2}\) is one of the major sources of titanium metal and titanium dioxide, which is used as a pigment in paints, cosmetics, plastics, rubber, and textiles [1, 2, 3]. To produce titanium dioxide, the ilmenite feed is first upgraded to a titanium oxide product [4, 5]. From the upgraded product, TiO\({}_{2}\) is commercially produced either by the sulfate or chloride route [6, 7]. The sulfate route, though it can use lower grade ores, is generally expensive and less environmentally friendly, whereas the chloride route is limited to high-grade feedstocks as the impurities can affect the stability of the fluidized bed [8]. The up-gradation of ilmenite is performed by carbothermic reduction to remove iron oxide. It can be conducted either by solid-state reduction at around 1200 \({}^{\circ}\)C, where synthetic rutile is produced or in a fully liquid state above 1600 \({}^{\circ}\)C where a high titania slag is produced with pig iron as a by-product [9, 10, 11]. In the smelting of ilmenite, the iron oxide in ilmenite is reduced by a suitable carbonaceous reductant to metallic iron, resulting in a high titania slag containing 75-95% TiO\({}_{2}\), of which slags with titania content above 85% are used for the chloride route and others for the sulfate route [12]. The reductant used is a carbonaceous material, such as anthracite, petroleum coke, metallurgical coke, etc. [13]. The smelting process of ilmenite is an unusual case where slag is the primary product, and the by-product is a valuable raw material to get pig iron and other metallic components [14, 15]. The titania slag forms a single phase with a stoichiometry of M\({}_{3}\)O\({}_{5}\)[16] and is a molten mixture of Ti\({}_{3}\)O\({}_{5}\), FeTi\({}_{2}\)O\({}_{5}\), MnTi\({}_{2}\)O\({}_{5}\), Al\({}_{2}\)TiO\({}_{5}\), MgTi\({}_{2}\)O\({}_{5}\), V\({}_{2}\)TiO\({}_{5}\), and Cr\({}_{2}\)TiO\({}_{5}\). M\({}_{3}\)O\({}_{5}\) is a solid solution, which is called pseudobrookite, and is present in major quantities in the slag with a small amount of rutile and ilmerite [17; 18; 19]. Pseudobrookite is only formed when the reduction of ilmenite happens at a temperature f more than 1200 \({}^{\circ}\)C, below which rutile and ilmenite are the dominant phases [20; 21]. The trivalent cations in the slag are easily oxidized if the slag comes into contact with oxygen or any oxidizer and the oxidation reaction is highly exothermic [22; 23]. As the slag is very easily oxidized, an inert gas (such as Ar) is used when the slag is produced in the laboratory to prevent oxidation. The impurities in ilmenite, such as CaO, MgO, Al\({}_{2}\)O\({}_{3}\), SiO\({}_{2}\), and MnO\({}_{2}\), are carried into the slag and can affect the slag if present in large quantities [24]. However, most of the ilmenite ores have a concentration of the impurities in quantities that do not affect the slag formation or its properties significantly. [PERSON] and [PERSON] [25] produced synthetic slag for preparing ternary diagrams using TiO\({}_{2}\), Ti\({}_{2}\)O\({}_{3}\), Fe, and Fe\({}_{2}\)O\({}_{3}\) but without any other impurities. No further data were found in the literature where the liquid slag phase boundary was measured using saturation experiments. [PERSON] and [PERSON] [25] investigated the slag model to assess the slag condition based on the ternary diagram. In the present work, several impurities will be used to replicate the industrial slag system. Such slag samples can be utilized to prepare calibration curves using various spectroscopic techniques, thus improving the accuracy of the system. In this paper, the phase study of synthetic ilmenite slags that were prepared in an induction furnace under a controlled argon atmosphere is reported. A phase study is carried out to determine the phases that are formed and to verify their similarity with the industrial slag. M\({}_{3}\)O\({}_{5}\) slag composition is a characteristic for ilmenite slags, and the effect of the quantity of various components on the phases formed are studied.