Structural FTIR spectra and thermal properties of CdO-B_2O_3 glasses doped with LiF, CaF_2 or TiO_2, together with X-ray diffraction and SEM investigations of their glass-ceramic derivatives

摘要

Binary cadmium borate (CdO 40-B2O3 60mol%) glass together with samples with the same basic composition and doped with 2% of either LiF, CaF2 or TiO2 were prepared by melting-annealing technique. Samples of these prepared glasses were thermally heat-treated to convert them to their corresponding glass-ceramic derivatives. FTIR spectral measurements were carried out to identify the constitutional network building units. IR results indicate the identification of both triangular BO3 and tetrahedral BO4 groups in their characteristics vibrational different wavenumbers. These IR vibrational spectra were assigned to their origin and they confirm that CdO like any alkali or alkaline earth oxide shares in the modification of some BO3-BO4 groups to their specific limit. The dopants show minor variations on the IR spectra due to their low percent. X-ray diffraction patterns identify the crystalline phases which were separated during thermal heat-treatment and the dopants were efficient in acting as nucleating agents and sharing in the crystalline phases formed. The base glass-ceramic is composed of cadmium metaborate only while the dopants change this phase to cadmium pyroborate beside a lithium borate or calcium borate phases while with TiO2 forms brookite crystalline phase beside cadmium pyroborate. Thermal expansion measurements for the studied glasses reveal similar progressive increase in thermal expansion coefficient, but the dilatometric softening temperatures exhibit distinct decrease with the dopants supporting the assumption that the dopants are situated in modifying positions. SEM technique was performed to ensure the morphological structures which exist along with addition of different dopants.