Lanthanide ions possess unique optical characteristics and can be used as luminescent probes; however, the characteristics and effect of lanthanide ion incorporation into metal-oxide host matrices have not been thoroughly researched up until now. In this study, we investigate the incorporation characteristics of \(\hbox {Eu}^{3+}\) such as whether threefold or fourfold-coordinated oxygen vacancies are created, the charge of the created oxygen vacancies, and whether the lanthanide ions incorporate in pairs or as single ions. Undoped, 5 at.% Eu and 5 at.% Eu, 5 at.% Nb-doped \(\hbox {HfO}_2\) were synthesized by sol–gel and combustion methods. All samples were of monoclinic phase. Photoluminescence, thermoluminescence, XRD, and luminescence decay kinetics were used to determine the impact of dopants on the \(\hbox {HfO}_2\) matrix. A mechanism for \(\hbox {Eu}^{3+}\) ion incorporation in pairs or individually is considered.
