Solid-state analytical chemistry : surface and bulk characterization by complementary analytical methods

Abstract

In the organic laboratory, chemists often use a standard set of analytical techniques such as NMR and IR spectroscopy to get a pretty good idea about the identity of the compounds at hand. In solid-state chemistry, on the other hand, usually no single method is able to provide a clear picture of the exact identity of the sample to be analyzed; thus, a large pool of complementary analytical methods is needed. This thesis discusses the selection and application of such complementary methods on three examples of solid-state materials: perovskite type metal fluorides (the REEL Project), tri-metal oxide analysis, and the analysis of metal nitride fluorides. The major goals of the NSF funded REEL Project are to introduce laboratory based research into first and second year chemistry courses, to generate new knowledge in the chemical sciences,and to increase the retention and graduation rates in science fields in the state of Ohio. In an attempt to replace heavy toxic metals such as Cd, Hg, and Pb in inorganic red and yellow pigments by more environmentally benign alternatives, students enrolled in General Chemistry II laboratory classes at YSU synthesized new materials of the type KMF3 that have two different transition metals at the M site. A series of mixed metal fluoride samples of the type KCoxCu1-xF3, where x= 0 to 1.0, were prepared and characterized using X-ray diffraction (XRD) by the students. These samples were subsequently further analyzed via scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM/EDS) and XRD to quantitatively determine the percent compositions and structures of the samples. The KCoxCu(1-x)F3 powder sample analyses showed that the expected compounds were obtained and with the appropriate percent composition. Also, the results represent the first known preparation of KCoxCu(1-x)F3 phases and demonstrated that sample color can be tuned by varying Co vs. Cu content. In the second example, and expected ternary tri-metal oxide sample, BaT1Ni2Ox, was studied using SEM/EDS, X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), Fourier-transform infrared spectroscopy (FT-IR) and XRD to identify the composition of the compound material and to determine whether these conformed with the reported X-ray diffraction data provided by the submitting research group. The bulk analysis of the compound shows the presence of multiple compounds, NiO, BaO, BaCO3, and T12O3. Therefore, ti was demonstrated that the expected compound, BaT1Ni2Ox was not obtained. The third example deals with the analysis of mixed anion materials such as inorganic nitride-fluorides. In these species, the anion composition of a model oxide compound is changed by the substitution of one N3- and one F- for two O2-ions while the cation composition is left unchanged. Thus, the purpose of this project is to investigate the Ti-N-O-F system to study the possibility of turning color as a function of nitrogen content, and also quantify the composition versus color of the compound. Additionally, the attempted synthesis of other metal nitride-oxide-fluorides such as Ca2Mn2N2O2F was undertaken. Dr. Wagner's Research group has synthesized these expected nitride fluoride compounds, and submitted them for characterization. SEM/EDS, Laser Raman spectroscopy, XPS, and XRD were selected as methods to determine the composition of the compounds. Analysis of the expected Ti-N-O-F series (brown, green, green/yellow, yellow) showed various compounds were present such as TiO2, CaO, and TiOF2, with nitrogen presented in all of the compounds. Thus, it is believed that the amount of nitrogen is the cause for the color change in the compounds. Furthermore, elemental analysis of the expected Ca2Mn2N2O2F using EDS and Raman proved to be calcium ferrite.