Characterization of molybdenum and tungsten phosphates compounds prepared using ammonium phosphate salt as flux

Abstract

Fusion of powdered molybdenum and tungsten oxide using ammonium phosphate salt as flux (ratio: 1:25 respectively) yielded soluble products which were unstable. The yellow (Mo) and purple-blue (W) solutions in deionized water, methanol and acetone decolorized within 3–5 hours. Infrared analysis of molybdenum and tungsten products revealed characteristic broad bands bearing two minor peaks in the region of 1040–1130 cm^-1 which reflects the simultaneous existence of PO₂ and PO₃ groups. SEM-EDX quantitative analysis results showed percentage weight of the identified elements in the increasing order of Mo or W < P < O with molybdenum product having 7.1%wt (Mo), 37.2%wt (P) and 53.5%wt (O) whilst tungsten product had 10.3%wt (W), 24.7%wt (P) and 46.5%wt (O). The EDX results indicated the presence of polyphosphate products whilst the SEM images showed microscopic crystalline product of molybdenum and a hygroscopic product of tungsten. XRD patterns of both molybdenum and tungsten products corresponded to the standard (JCPDS) pattern of molybdenum oxide phosphate MoO₂(PO₃)₂ and tungsten oxide phosphate (WO₂(PO₃)₂), respectively.

KEY WORDS: Molybdenum, Tungsten, Ammonium phosphate flux, Polyphosphates

Bull. Chem. Soc. Ethiop. 2019, 33(1), 103-112

DOI: https://dx.doi.org/10.4314/bcse.v33i1.10