Crystallization behavior of glasses from the system CdO-B2O3 with varying CdO contents (30–90 mol%)

Abstract

A novel study on the crystallization behavior of extended cadmium borate glasses with varying CdO contents (30–90 mol%), has been carried out. Collective structural FTIR spectral measurements were made for the parent cadmium borate glasses and their glass-ceramic derivatives to identify the structural building groups within the prepared glasses and their crystalline derivatives. X-ray diffraction together with scanning electronic microscopic analysis of the prepared glass-ceramic were done to find out the formed crystalline phases upon thermal heat treatment with two-step regime and identifying the morphological features of the formed crystalline phases. FTIR spectral data reveal the appearance of both the vibrational bands due to triangular and tetrahedral borate groups irrespective of the high CdO content but with varying intensities. The tetrahedral borate (BO4) groups are identified to possess their vibrational modes within the wavenumber 800-1200 cm-1 while the triangular borate (BO3) groups are vibrating within the range 1200–1600 cm-1. The glass-ceramics reveal similar FTIR spectra but with distinct sharpness and the generation of a further IR band at 1060 cm-1 due to formed distinct crystalline tetrahedral structures (such as triborate, pentaborate, diborate). X-ray diffraction patterns indicate the formation of main crystalline phases of cadmium borates with increasing the ratio of CdO to B2O3 by increasing the CdO content (CdO·2B2O3 → CdO·B2O3 → 3CdO·2B2O3→ 2CdO·1B2O3). The ease of crystallization of the studied binary CdO-B2O3 glassy system is assumed to be related to the presence of phase separation in this divalent borate glassy system as other related divalent borate glasses and hence thermal heat-treatment of the parent glasses leads to voluminous crystallization.