X-ray powder diffraction quantitative analysis performed in situ at high temperature: application to the determination of NiO in ceramic pigments

Although nickel(II) oxide (NiO) is a potential carcinogenic agent, it is st ill used in the synthesis of ceramic pigments because during their preparat ion at high temperature, NiO is thought to combine with other compounds, cr ystallizing as new phases with spinel-like structures. Unfortunately, there are no widely accepted methods for the determination of free NiO in cerami cs, the main reason being experimental difficulties. In fact, quantitative phase analysis (QPA) by X-ray powder diffraction (XRPD) may fail because di ffraction peaks of NiO with space group Fm (3) over bar m and a similar or equal to 4.18 Angstrom overlap with those of the spinel with space group Fd (3) over bar m and a similar or equal to 8.4 Angstrom. To overcome this pr oblem, in this work QPA has been performed in situ at high temperature to r esolve the peak overlap of NiO and spinel by taking advantage of the differ ent thermal expansion of each phase. It is believed that this is the first report of the application of this technique.