Henry J. Spratt

Infrared and near-infrared spectroscopic study of synthetic hydrotalcites with variable divalent/trivalent cationic ratios

Near-infrared (NIR), X-ray diffraction (XRD) and infrared (IR) spectroscopy have been applied to hydrotalcites of the formula Mg(6) (Fe,Al)(2)(OH)(16)(CO(3)).4H(2)O formed by intercalation with the carbonate anion as a function of divalent/trivalent cationic ratio. Such hydrotalcites were found to show variation in the d-spacing attributed to the size of the cation. In the IR (1750-4000cm(-1)), the position of all bands except those at approximately 3060cm(-1) shift to higher wavenumbers as the cation ratio increases. Conversely, at wavenumbers below 1000cm(-1), the bands shift to lower wavenumbers as the cation ratio increases. A water bending mode at higher wavenumbers was also observed which indicates that the water is strongly hydrogen bonded. In the NIR spectrum between 8000 and 12,000cm(-1), there is a broad feature which is attributed to electronic bands of the ferrous ion and low intensity sharp bands due to overtones of the OH stretching vibrations. It is also apparent from this region that Fe(2+) substitutes for Mg(2+). The intensity of bands at 7750 and 5200cm(-1) increases as the cation ratio increases in the NIR spectrum. Hydrotalcites with a magnesium amount 3 and 4 times greater than that of aluminium and iron combined, in the lower wavenumber region of the NIR spectrum, have very similar spectral profiles. This work has shown that hydrotalcites with different divalent/trivalent ratios can be synthesised and characterised by infrared spectroscopy.

Effects of metal ion concentration on electrodeposited CuZnSn film and its application in kesterite Cu2ZnSnS4 solar cells

In this study, effects of concentrations of Cu(II), Zn(II) and Sn(II) ions in the electrolytic bath solution on the properties of electrochemically deposited CuZnSn (CZT) films were investigated. Study of the composition of a CZT film has shown that the metallic content (relative atomic ratio) in the film increased linearly with increase in the metal ion concentration. It is the first time that the relationship of the compositions of the alloy phases in the co-electrodeposited CZT film with the concentration of metal ions has been revealed. The results have confirmed that the formation and content of Cu6Sn5 and Cu5Zn8 alloy phases in the film were directly controlled by the concentration of Cu(II). SEM measurements have shown that Sn(II) has significant impact on film morphology, which became more porous as a result of the larger nucleation size of tin. The changes in the surface properties of the films was also confirmed by chronoamperometry characteristic (i–t) deposition curves. By optimization of metal ion concentrations in the electrolyte solution, a copper-poor and zinc-rich kesterite Cu2ZnSnS4 (CZTS) film was synthesized by the sulfurization of the deposited CZT film. The solar cell with the CZTS film showed an energy conversion efficiency of 2.15% under the illumination intensity of 100 mW cm 2.