Raman and 27Al NMR structure investigations of aluminate glasses: (1−x)Al2O3−x MO, with M=Ca, Sr, Ba and 0.5<x<0.75)

Structure-property relations in calcium aluminate glasses containing different divalent cations and SiO 2

“…The two bands around 540 and 780 cm −l are present in all of the samples. The 540 cm −l Raman band shifts to slightly lower frequencies with increasing size of the divalent cation, in agreement with a previous observation [24]. This shift to lower frequency results from a decrease in the Al-O force constant, suggesting that the different modifier cations are closely connected to the Al-O-Al linkages.…”

“…1a and b, respectively. The spectrum of the binary eutectic CaOAl 2 O 3 composition (CaAl) is in good agreement with those already published [22][23][24][25]. This Raman spectrum consists of a band around 540 cm −l and another band near 780 cm −1 with a marked tail to higher frequency.…”

“…This Raman spectrum consists of a band around 540 cm −l and another band near 780 cm −1 with a marked tail to higher frequency. The former band has been attributed to transverse motions of bridging oxygens within the Al-O-Al linkages [22][23][24][25], whereas the band at 780 cm −1 has been assigned to Al-O stretching vibrations of the tetrahedral aluminate groups [4]. Moreover, the CaAl glass exhibits a weak sharp peak at 1015 cm − 1 , which is presumably because this composition is not completely amorphous [18].…”

Structure of liquid tricalcium aluminate

“…Sample reproducibility was checked by unpolarized Raman spectra measured for the glass samples at room temperature by using a T64000 Jobin Yvon confocal micro-Raman spectrometer equipped with a CCD detector with the 514.532 nm line of a Coherent Ar + laser as the excitation source. The spectra are consistent with previous Raman measurements of Ca 3 Al 2 O 6 glass [11,22], exhibiting a strong band at 756 cm −1 , attributed to a symmetric vibration of Q 2 species, and a medium-intensity band at 560 cm −1 .…”

“…In a conventional furnace, glasses in the (CaO) x (Al 2 O 3 ) 1−x system can be formed in a narrow composition range close to the eutectic composition (x = 0.64) [10]. Levitation techniques enable the extension of the glass-forming region to 0.46 x 0.75 [11], where tricalcium aluminate (Ca 3 Al 2 O 6 ) represents the CaO-rich glass end-member at x = 0.75. The local aluminum coordination environment can be determined in this three-component system by using conventional neutron and x-ray diffraction combined with aerodynamic levitation methods [12,13].…”