Structural and Spectroscopic Characterization of Tb³⁺-Doped MgAl₂O₄ Spinel Ceramics Fabricated by Spark Plasma Sintering Technique

Spark plasma sintering (SPS) technique is successfully used for the preparation of magnesium aluminate spinel ceramics doped with different concentrations of Tb³⁺ ions. Structural, morphological, optical, and photoluminescence (PL) characterization are conducted. It is demonstrated that the redshift in the absorption spectra is possibly due to the energy gap between the valence and conduction bands reducing and the formation of a higher concentration of nonbridging oxygen with an increase in the concentrations of Tb³⁺ ions in MgAl₂O₄ ceramics. The PL spectrum excited by nitrogen laser consists of a broad emission band with a maximum at λ_em ≈ 400 nm and a series of emission bands in the 400–700 nm spectral range responsible for Tb³⁺ ions. In the “blue” spectral region, the complex host centers such as oxygen vacancies are recorded. An increase in the terbium ion concentration does not lead to the effect of concentration quenching. Luminescence decay kinetics analysis for all ceramics samples is performed. The effect of terbium oxide on the optical, PL properties and luminescence decay kinetics of MgAl₂O₄ ceramics is discussed.