<p>Tb-doped <i>AE</i>₂Gd₈(SiO₄)₆O₂ (<i>AE</i> = Mg, Ca, Ba) oxyapatite single crystals were synthesized using the floating zone method, and their photoluminescence (PL) and scintillation properties were investigated and compared with the reported results for Tb-doped Sr₂Gd₈(SiO₄)₆O₂. The samples exhibited emission peaks at 315 nm and in the 380–625 nm range, which were attributed to the 4f–4f transitions of Gd³⁺ and Tb³⁺ ions, respectively. The PL and scintillation decay time constants were on the order of 1 ms, which was a typical value for Tb³⁺ ions. The PL quantum yield was approximately 70%, showing negligible variation among samples. The scintillation light yields, estimated from the pulse height spectra under&#xa0;¹³⁷Cs <i>γ</i>-ray irradiation, were 4800 (<i>AE</i> = Mg), 9700 (Ca), 14,600 (Sr), and 6300 photons/MeV (Ba).</p>