Ceramic pigments from CoxNi3-xP2O8 (0 ≤ x ≤ 3) solid solutions

Abstract

CoxNi3-xP2O8 (0 ≤ x ≤ 3) solid solutions were synthesized via the chemical co-precipitation method. Variation of unit cell parameters and interatomic distances indicated that these solid solutions with the Ni3P2O8 structure are stable between 800 and 1200 °C in compositions with 0 ≤ x ≤ 1.5 and between 800 and 1000 °C when (0 ≤ x ≤ 3). When (2.5 ≤ x ≤ 3.0), the solid solutions lead to the Co3P2O8 structure, being stable between 800 and 1000 °C.

The yellow colour of the Ni3P2O8 compound changes to pink or red when Co(II) ions are incorporated in the structure as Ni3P2O8 solid solutions are formed. Bands corresponding to second and third electronic transitions of the Co(II) ions in octahedral coordination appear in the 450–600 nm in the UV-V spectra, and they are responsible of the observed changes in the colour. Absorbance in the visible spectra was also obtained from enamelled samples but a new band at 650 nm with considerable absorbance when x > 1.0 increased the blue amount, and colour of the enamelled samples was yellowish brown, brown, green and blue.