Structural characterization and colour of Ni3−xCuxP2O8 (0 ≤ x ≤ 3) materials

The structural characterization of Ni3−xCuxP2O8 (0.0 ≤ x ≤ 3.0) compositions was performed and the colour parameters of these materials measured. Solid solutions with Ni3P2O8, Ni2CuP2O8 and Cu3P2O8 structures were obtained and the compositional range in which they are formed was established. Structural distortion was detected in these solid solutions when x increases from the variation in the unit cell parameters and that of the interatomic distances. Solid solutions with Ni3P2O8 structure are stable at 1200 °C and may be used as ceramic pigments. Changes in the colour of these materials were related to the structural changes. Yellow materials are obtained from Ni3−xCuxP2O8 solid solutions with a Ni3P2O8 or Ni2CuP2O8 structure and a gradual change from yellow to brown is obtained with the introduction of Cu(II) in the Ni3P2O8 structure, 0.0 ≤ x ≤ 0.7 at 1200 °C.