Influence of Metal Components Composition in Zinc Phosphate Films on Infrared and Laser Raman Spectra and Their Anti-Alkaline Property

Abstract

By measuring the infrared spectra and laser Raman spectra for various hopeite films and phosphophyllite films, the influence of metal component composition in these films on those spectra can be investigated. In infrared spectra, peaks corresponding to (ν₁ + ₃) andν₄, the fundamental vibrational modes of PO₄^3-, were seen, but the peak patterns ofν₄, were d ifferent for hopeite films containing manganese component from that not containing it (Figs.2, 3, 5 and 6). Raman s pectra for these films were shown in Figs.7-11. Four clear peaks due to PO₄^3-were found in the region of 800-1300 cm^-1. Tetrahedral orthophosphate (PO₄^3-) has four fundamental vibrational modes ofν₁, ν₂, ν₃, and_ν, (Fig.4) ;_ν1, andvν₃are observed in 800-1300 cm^-1. Essentially, ν₃ degenerates triply. But in the crystalline state of zinc phosphate films, the tetrahedral structure of PO₄^3- will be deformed, and the degeneracy of ν₃ is untied and the band is split to three peaks. Accordingly, it was considered that the spectra with four peaks containing ν₁ were generated. Here, main peak corresponds to ν₁ and other th ree peaks correspond toν₃. This consideration was supported by the Raman data for 85%-H₃PO₄solution (Fig.12). The peak fr equencies of Raman bands for various zinc phosphate films were compared (Table 2). For both hopeite films and phosphophyllite films, the Raman peaks shifted to lower wavenumbers with the increase of nickel or manganese component (Fig.13). In particular, the Raman peaks of hopeite C and D was similar to that of phosphophyllite E. The composition of modified hopeite films by the doping of nickel or manganese comp onent has been analyzed as Zn_3-x Me_x(PO₄)₂-4 H₂0 (Me: Ni and/or Mn). This composition is different from neat hopeite films of Zn₃(PO₄)₂4 H₂0 and is modified to the composition as phosphophyllite films. Thus, it was possible to correlate the modification level of zinc phosphate films, for instance, the crystal morphologies of these films or chemical stability like anti-alkaline property with the observation of PO₄^3- peak shift in Raman spectra.