Influence of metal components in Hopeite films on IR and laser Raman spectra

Abstract

Hopeite films on galvannealed steel were formed in various zinc phosphate solutions. The metal component composition of various Hopeite films was determined by atomic absorption. By measuring the infrared (IR) spectra and the laser Raman spectra for these films, the influence of metal component composition on these spectra could be investigated. In IR spectra, peaks corresponding toν ₃ andν ₄, the basic vibration mode of PO ³⁻₄ , were seen, but the peak patterns ofν ₄ were different for Hopeite containing manganese and that not containing it. In the Raman spectra, four clear peaks for various films were found in the region 1300 to 800 cm⁻¹ . Although these spectra are due to PO ³⁻₄ ,ν ₁ andν ₃ are found in this region. Essentially,ν ₃ degenerates triply, but in the crystalline state of Hopeite films, the symmetry of the regular PO ³⁻₄ tetrahedron will be distorted by the interaction. At that moment, the degenerations ofν ₃ are untied and split into three peaks. Thus it was thought that spectra with four peaks ofν ₁ were generated. However, the main peak corresponds toν ₁ and other three peaks correspond toν ₃. The values of the Raman band for various Hopeite films were compared. The band shifted to the lower wavenumber region according to the increase of manganese or nickel in these films. The structure of Hopeite films modified by the action of manganese or nickel has been analysed to be Zn_3−x Me _x (PO₄)₂ · 4H₂O (Me = Mn or Ni), but this structure is different from that of normal Hopeite films (Zn₃(PO₄)₂ · 4H₂O).