Zinc oxide optical ceramics were prepared by the hot uniaxial pressing technique. Nominally undoped and gallium- and indium-doped ceramics were studied. Undoped ceramics with a thickness of 0.5 mm had a total transmittance of about 65% in the visible range and exhibited mainly deep level luminescence at 600 nm. Doping of the ceramics resulted in the appearance of free charge carriers, suppression of the defect emission band, and enhancement of the excitonic luminescence intensity. The typical concentration of donor centers in doped ceramics was on the order of 10 ¹⁹ cm ^-1 . Admixture of the dopants also decreased the average grain size of the ceramics and, in the case of indium-doped ceramics, affected their morphology. With respect to the excitonic emission intensity, the optimal concentration of dopants was 0.028 at% of Ga ³⁺ and 0.045 at% of In ³⁺ . The maximum intensity of excitonic luminescence in indium-doped ceramics was about 1.5 times higher than that in gallium-doped ones. Luminescence decay curves of the ceramics with suppressed defect emission had a main decay time constant of 0.7 ns.

The presented work is dedicated to the study and comparison of scintillating properties of zinc oxide samples prepared in different morphologies: whiskers, nanowalls, multipods, and ceramics. It was shown that total transmittance, photo- and radioluminescence spectra, and radioluminescence kinetics can vary significantly depending on sample structure and preparation conditions. The highest total transmittance was registered for ZnO ceramics (>50% at 0.5 mm thickness). Differences in the transmittance of whiskers, nanowalls, and multipods can be attributed to their shape and thickness which affects the amount of light refraction and scattering. The study of radioluminescence demonstrated that all samples, except undoped ceramics and air annealed whiskers, have predominantly fast luminescence with a decay time <1 ns. High transmittance of ceramics opens the way for their use in the registration of high energy X-ray and gamma radiation, where a large volume of scintillators is required. In cases, where large scintillator thickness is not a necessity, one may prefer to use other ZnO structures, such as ensembles of whiskers and nanowalls. Studies of near-band-edge luminescence components at low temperatures showed that the structure is quite similar in all samples except Ga doped ceramics.

The shift of the conduction band (CB) edge for thirty different (Lu,Gd)₃(Ga,Al)₅O₁₂:Ce compositions, with simultaneous variation in Lu/Gd and Ga/Al content was studied using thermally stimulated luminescence (TSL). Specific TSL peaks were related to impurities of Ta, Cr, Yb, Ti and Eu in Lu₁Gd₂Ga₃Al₂O₁₂:Ce ceramics. The shift of Yb-related peak positions (in temperature and trap depth) with composition modification was investigated as well. In Gd-containing (Lu,Gd)₃(Ga,Al)₅O₁₂ compositions a non-monotonous shift of the CB edge with increasing Ga content has been affirmed. The difference between thermal trap depths evaluated from our TSL experiments and optical trap depths obtained from the literature was explained by the role of lattice relaxation.