Study of optical constants and dielectric properties of nanocrystalline α-cordierite ceramic

Abstract

The nanocrystalline 2 Mg.2Al 2 O 3 .5SiO 2 as amorphous-type α-cordierite was prepared by the modified sol-gel (or Pechini) technique. After calcination at 800ºC, the pressed powder as disk pellets was sintered at 1150ºC, 1250ºC, and 1350ºC. The structural information of α-cordierite was obtained by X-ray diffraction (XRD), scanning electron microscopy (SEM), micro-Raman scattering spectra, and Fourier transform infrared (FTIR) spectra. The XRD and Raman spectra showed that the nanocrystalline α-cordierite phases from pellets of glass-ceramic powders appeared when the temperature increased. The SEM results confirmed the rounded shape of the nanocrystalline α-cordierite. Using Kramers-Kronig (KK) method, the FTIR spectroscopy was evaluated. The increasing synthesized temperature increased the size of nanocrystalline. Furthermore, by increasing the synthesized temperatures the optical constants of nanocrystalline, both real and imaginary parts of the refractive index and dielectric function decreased. Consequently, the transversal optical (TO) and longitudinal optical (LO) phonon frequencies shifted to red frequencies by increasing reaction temperature.

Synthesis and Characterization of MIL–101 (Cr) Adsorbent Coating on Microchannel Walls for Water Adsorption Heat Pumps

“…84−1222). 41 In the MIL-101 (Cr) case, the diffraction patterns primarily show characteristic peaks of two phases between 5 and 10°, typical for MIL-101 (Cr), and other characteristic diffraction peaks between 17 and 35°, which are typical for the presence of terephthalic acid. 45 While comparing diffraction peaks of the coated samples, almost all the composite peaks coincide entirely with that mentioned for cordierite.…”

“… In the case of cordierite, from the same figure, diffraction peaks can be observed at 10.8, 18.3, 19.2, 21.9, 26.6, 28.7, 29.6, and 34.1° referred to 10 hkl miller planes of cordierite corresponded to (100), (110), (002), (102), (112), (202), (211), and (212), respectively, which are assigned to α-cordierite (JCPDS card no. 84–1222) . In the MIL-101 (Cr) case, the diffraction patterns primarily show characteristic peaks of two phases between 5 and 10°, typical for MIL-101 (Cr), and other characteristic diffraction peaks between 17 and 35°, which are typical for the presence of terephthalic acid .…”

“…The band that appeared with a moderate intensity peak at 746 cm –1 signifies mono-substituted benzene, while a similar peak at 583 cm –1 depicts the presence of stretching vibration due to Cr–O . In the case of cordierite, significant peaks are observed, which constitute peaks at 1179 cm –1 corresponding to tetrahedral bonds of AlO 4 . , Moreover, peaks at 1080–1088 cm –1 depict the existence of Si–O bands, whereas the band at about 750 cm –1 corresponds to absorption bands of MgAl 2 O 4 . − The bands at about 525 cm –1 are ascribed to MgO 6 octahedral bands …”

“…38 In the case of cordierite, significant peaks are observed, which constitute peaks at 1179 cm −1 corresponding to tetrahedral bonds of AlO 4 . 39,40 Moreover, peaks at 1080− 1088 cm −1 depict the existence of Si−O bands, 41 whereas the band at about 750 cm −1 corresponds to absorption bands of MgAl 2 O 4 . 42−44 The bands at about 525 cm −1 are ascribed to MgO 6 octahedral bands.…”

Structural and Optical Coefficients Investigation of γ-Al2O3 Nanoparticles using Kramers-Kronig Relations and Z–scan Technique

“…Furthermore, when the sign of the real dielectric function changes from positive to negative, intermediate point of these two domains is TO frequency mode. In a similar situation, the intermediate point of the negative to positive data of real dielectric function is LO frequency mode [51]. In some literature, the TO and LO modes are the maximum position of ε 2 and ImðÀ 1 = ε Þ plots, respectively [39].…”