Heterovalent Zr4+-Cu2+ substitution in zirconium pyrophosphate: From theoretical models to synthesis and utilization

Heterovalent substitution in zirconium pyrophosphate (ZrP2O7) represents a particular interest due to limited theoretical knowledge in this area and technological importance of the related compounds. Our investigation is focused on Zr4+-Cu2+ substitution in the ZrP2O7 structure. The formulas Zr1−xCuxP2O7−x and Zr1−xCu2xP2O7 represent the general composition of the studied solid solutions which correspond to two cross sections, i.e. ZrP2O7-CuP2O6 and ZrP2O7-Cu2P2O7, of the ternary oxide system ZrO2-CuO-P2O5. Phase relations in the systems over the whole concentration range have been studied using XRD analysis. Formation of new solid solutions Zr1−xCu2xP2O7 on basis of the ZrP2O7 structure has been established in the homogeneity range 0 < x < 0.08. Some of the obtained compositions in the ZrP2O7-Cu2P2O7 system with attractive cyan-green colouration have been characterised as inorganic pigments with regards to their colour properties, particle size, morphology, and stability.