The surface chemistry of amorphous zinc polyphosphates of different compositions (ranging from zinc metaphosphate to zinc orthophosphate) has been investigated by means of X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary-ion mass spectroscopy (ToF-SIMS). The identification of the chain length of zinc polyphosphates by XPS could be achieved on the basis of the integrated intensity ratio of the bridging (P-O-P) and non-bridging (P=O and P-O-M) oxygen peaks used for fitting the oxygen 1s signal, the shift of the P 2p3/2 signal towards lower binding energies, and of the modified Auger parameter towards higher values as the zinc content increases. The discrimination of the polyphosphate chain lengths could be also achieved by ToF-SIMS, by comparing the intensities of selected characteristic phosphate fragments. Both techniques appear to be suitable for the investigation of polyphosphate glasses in applications such as tribology, where there is a need to identify the chain length present in the outermost monolayer of the film. Fourier-transform infrared (FT-IR) spectroscopy was used in order to characterize the bulk compounds. The FT-IR studies showed that long-chain structures linked through P-O-P bonds predominate in the metaphosphate composition, while upon increasing the Zn content, the chains become shorter, ultimately being replaced by PO4 monomers in the orthophosphate composition.
Chain-Length-Identification Strategy in Zinc Polyphosphate Glasses by Means of XPS and ToF-SIMS
ROSSI, ANTONELLA;
2012-01-01
Abstract
The surface chemistry of amorphous zinc polyphosphates of different compositions (ranging from zinc metaphosphate to zinc orthophosphate) has been investigated by means of X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary-ion mass spectroscopy (ToF-SIMS). The identification of the chain length of zinc polyphosphates by XPS could be achieved on the basis of the integrated intensity ratio of the bridging (P-O-P) and non-bridging (P=O and P-O-M) oxygen peaks used for fitting the oxygen 1s signal, the shift of the P 2p3/2 signal towards lower binding energies, and of the modified Auger parameter towards higher values as the zinc content increases. The discrimination of the polyphosphate chain lengths could be also achieved by ToF-SIMS, by comparing the intensities of selected characteristic phosphate fragments. Both techniques appear to be suitable for the investigation of polyphosphate glasses in applications such as tribology, where there is a need to identify the chain length present in the outermost monolayer of the film. Fourier-transform infrared (FT-IR) spectroscopy was used in order to characterize the bulk compounds. The FT-IR studies showed that long-chain structures linked through P-O-P bonds predominate in the metaphosphate composition, while upon increasing the Zn content, the chains become shorter, ultimately being replaced by PO4 monomers in the orthophosphate composition.
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