Effect of niobium pentoxide (Nb2O5) on the microstructure and properties of the diopside glass-ceramics produced from Bayan Obo mine tailing

Influence of Niobium Pentoxide and Sintering Temperature on Mechanical and Electrical Properties of Glass-ceramics Obtained from Recycled Automotive Windshields

“…This event is likely associated with the glass transition temperature, Tg. Zhao et al 26 reported the Tg was close to 635 °C for glass-ceramics produced with vitreous materials of similar composition with Nb 2 O 5 addition. Nonetheless, they also did not observe a significant influence of Nb 2 O 5 on Tg.…”

“…Samples of 3.0 g were compacted in a circular metal die, with a diameter of 24.0 mm, applying a uniaxial pressure of 25.8 MPa for one minute (P10 ST, 98 kN hydraulic press, Bovenau, Brazil). The shaped specimens were dried in an oven (400/3ND, New Ethics, Brazil) at 110 °C for 1.0 h. Subsequently, the samples were sintered in a muffle furnace (N1100, Fornitec, Brazil) with a heating rate of 5.0 °C/min at the final temperatures of 700 or 800 °C for 1.0 h. Based on works in which glassceramics were produced from raw materials similar to the windshield glass 5,15,19,23,26 , the adopted sintering temperatures were 700 and 800 °C. These temperatures were probably higher than glass transition temperature (Tg) and close to the crystallization temperature (Tc).…”

“…Niobium pentoxide has attracted interest because it affects relevant properties of glasses and glass-ceramics; in these materials, niobium oxide can change density, dielectric constant 26 , crystallinity 27,28 , chemical stability 13 , and biocompatibility 13 . It is used as a nucleating agent 27,29 to promote crystallization that influences the optical and dielectric properties of glass-ceramics 30 .…”

“…Thus, it has been used in the products such as batteries, solar cells, supercapacitors, prostheses, and even as dental material 31,32,33 . Nevertheless, as Zhao et al 26 reported, the effects of this nucleating agent on the microstructure and properties of glass-ceramics are not yet clearly understood. In their work 26 , the addition of niobium pentoxide increased the dielectric constant of glass-ceramics.…”

“…Nevertheless, as Zhao et al 26 reported, the effects of this nucleating agent on the microstructure and properties of glass-ceramics are not yet clearly understood. In their work 26 , the addition of niobium pentoxide increased the dielectric constant of glass-ceramics. This effect was related to the formation of the calcium pyroniobate phase, which has a dielectric constant higher than diopside that was the predominant phase in glass-ceramics produced without niobium oxide as nucleating agent.…”