Journal of Ceramic Processing Research. Vol. 18, No. 9, pp. 691~695 (2017) 691 J O U R N A L O F Ceramic Processing Research The role of Sb 2 O 3 on the physical and structural properties of PbO-SiO 2 glasses Negin Allahmoradi, Saeid Baghshahi * and Masoud Rajabi Department of Materials Science and Engineering, Facult of Engineering, Imam Khomeini International University, Qazvin, Iran Lead glasses are widely used in nuclear applications, particularly for shielding purposes. In this research, glasses with the general composition of 65PbO·(35-x)SiO 2 ·xSb 2 O 3 , where x = 0, 1, 2, 3, 4 and 5 were produced using the conventional method of melting and casting. The physical properties of the glasses were investigated using optical and electron microscopy, thermal analysis and FT-IR methods. The experiments showed that duo to phase segregation, the samples containing 4 and 5 molar of Sb 2 O 3 were not completely glassy. The results revealed that with the rise of Sb 2 O 3 content, the glass density increased from 6.33 to 6.95 g.cm -3 . Based on the thermal and FT-IR analyses, with increasing the amount of Sb 2 O 3 , antimony entered the glass structure with the formation of Si-O-Sb bondings. Consequently, in lower amounts, Sb 2 O 3 acted as fining agent, resulting in the reduction of the bubbles from about 1.8 to 0.7 vol.%, while when present in amounts exceeding 2 mole%, the bubble content slightly increased. Key words: Lead glass, Antimony addition, Glass structure, Fining agent, Physical properties. Introduction Lead glasses are widely used as gamma ray shields. These glasses usually have higher refractive indices than other glasses, which make them look smoother, shinier and more colorful. The PbO content of the ordinary lead glasses is usually about 24.4% wt., and in the shield glasses is usually up to 70 mole% [1]. Lead oxide plays the role of network modifier, when present in low amounts and network former when present in high amount [2]. In the binary system of PbO-SiO 2 , the glass can be easily formed with up to 70 mole% of PbO, and even up to 75 molar % in small samples. Based on the network theory, when the concentration of network modifier reaches 5%, all of the bridges would be broken and the glass formation is impossible. As an atomic point of view, Fajans et al. [3] have reported an acceptable reason for this phenomenon. Due to their potential application in nonlinear optical and broadband light amplifiers, Sb 2 O 3, heavymetal oxide glasses have recently gained great attention [4]. Heavy metal oxide glasses containing lead oxide or bismuth oxide show a high degree of radioactive resistance due to their high density and atomic number [5]. The glass making ability of Sb 2 O 3 has been predicted by Zakariasen. Available reports show the existence of Sb 5+ and Sb 3+ in phosphate glasses containing antimony [4]. According to the researches, the PbO-Sb 2 O 3 -As 2 O 3 glass system is highly resistant against crystallization [6]. Sb 2 O 3 is mostly added to the glass as a fining agent to remove the gas bubbles [4, 7]. In most glasses, 0.2 molar percentage of Sb 2 O 3 is used in conjunction with NaNO 3 or KNO 3 . The work conducted by Grund et al. [8] showed that the number of gas bubbles in silicate glass is reduced in the range of 1100-200 per 100 g glass by adding Sb 2 O 3 as a fining agent to the glass. Zhang et al. [9] also showed that the replacement of SiO 2 with 10 molar percent of Sb 2 O 3 in the structure of Bi 2 O 3 -B 2 O 3 -SiO 2 glass will increase T g . In other words, a lower amount of Sb 2 O 3 (< 5 mole%) would enhance the thermal stability of the glass. Changing the glass composition results in the formation of Si-O-Sb and Si- O-B bondings. It also leads to oxidation of Bi 3+ and its conversion to Bi 4+ and Bi 5+ . Silicate glasses are considered as the most conventional types of commercial glasses due their easy production process and great visible transmittance [10]. Due to its redox nature, Sb 2 O 3 is expected to reduce the number of bubbles and enhance the optical properties of these glasses. In this research, we will study the potential of Sb 2 O 3 as a fining agent in silicate glasses. In fact, this paper aims to investigate the effect of Sb 2 O 3 on the physical properties of lead silicate glasses. Experimental Procedures In order to prepare the samples, analytical grade PbO (CHEM-LAB), SiO 2 (Merck) and Sb 2 O 3 (Merck) were used. Samples with the general composition of 65PbO.(35-x)SiO 2 .xSb 2 O 3 in which x = 0, 1, 2, 3, 4, 5 were formulated (Table 1). The powders were milled *Corresponding author: Tel : +989122164225 Fax: +98-28-33780073 E-mail: baghshahi@eng.ikiu.ac.ir