Co2P2O7–Ni2P2O7 solid solutions: Structural characterization and color

Abstract NH 4 [Co 1− y Ni y PO 4 ]·H 2 O (0 ≤ y ≤ 1) single crystals were fired to prepare Co 2− x Ni x P 2 O 7 0 ≤ x ≤ 2 solid solutions between 800 and 1200°C. The structure of these solid solutions is α‐M 2 P 2 O 7 (M = Co, Ni). The contraction of the unit cell with increasing x confirmed the formation of these solid solutions. The UV–vis–NIR spectra of these solid solutions were consistent with Co( II ) and Ni( II ) ions in the two different crystallographic sites (octahedral site and square pyramidal site) in the α‐M 2 P 2 O 7 structure. Due to their thermal stability, Co 2− x Ni x P 2 O 7 (0 ≤ x ≤ 2) solid solutions with α‐M 2 P 2 O 7 structure can be used as a blue, green, brown or yellow ceramic pigment.