The coordination of Ni11 in glasses and glass-ceramics of the system MgOAl2O3SiO2

Evolution of the Ni2+ Environment During the Formation of a MgO–Al2O3–SiO2 Glass‐Ceramic: A Combined XRD and Diffuse Reflectance Spectroscopy Approach

“…The optical spectra of the glass up to a heat treatment of 950°C reflect a structural environment for Ni 2+ similar to that observed in other silicate and aluminosilicate glasses, i.e., a majority of [5] Ni 2+ , in TBP, and the presence of a minority of [4] Ni 2+ . There is no evidence of [6] Ni 2+ as previously suggested in similar compositions . A previous investigation on Ni‐MAS glasses has detected the presence of [6] Ni 2+ , but the initial glasses contain a significant proportion of NiAl 2 O 4 crystals, which are not detected by XRD in the present glasses.…”

“…The coefficient of thermal expansion and T g decreases with increasing NiO content . This is attributed to the formation of large size inhomogeneous regions in the glasses with increasing NiO contents, which was confirmed by small angle X‐ray scattering (SAXS) for Ni‐MAS glass nucleated by TiO 2 .…”

“…In glasses, Ni 2+ can adopt various coordination numbers with a wide range of associated colorations: fourfold ( [4] Ni 2+ ), fivefold ( [5] Ni 2+ ), and sixfold ( [6] Ni 2+ ) coordinations, giving, respectively, colorations from blue to brown and yellow‐green . A previous study of Ni 2+ environment in the MAS glass system concluded that Ni 2+ occupies essentially octahedral positions with minor amounts of tetrahedral sites . However, this study did not consider [5] Ni 2+ .…”

“…6,8 In recent years, studies have focused on improving the infrared emissing ability and understanding the crystallization sequence in Ni-MAS glass-ceramics. [5][6][7][9][10][11][12][13][14][15] Moncorge et al found that the fluorescence of Ni 2+ -doped crystals can be significantly improved by increasing the proportion of Ni 2+ in octahedral sites. 16 Since the fluorescence of Ni 2+ depends mainly on its local environment, it is therefore a crucial parameter.…”

Stoichiometric (Ni,Mg)‐Cordierite Glass–Ceramics

“…Beall and Pierson 8 observe a nickel aluminosilicate spinelloid crystallizing from NiO·MgO·Al 2 O 3 ·SiO 2 glasses. Although silica may be incorporated in the spinel phase crystallizing from Ni‐cordierite glasses, the spinel is not compositionally NiAl 2 O 4 as assumed in previous studies 6,7,32 …”