[en] Photoluminescence of Ce³⁺- and Pr³⁺-activated Sr₂GeO₄ powders was measured between 17 and 600 K. For both ions strong 4fⁿ⁻¹5dⁿ→4fⁿ (d-f) emission is observed at low temperatures, around 410 nm (Ce³⁺) and 280 nm (Pr³⁺). The Ce³⁺ d-f emission quenches starting at 150 K and disappearing completely just above room temperature. Pr³⁺ d-f luminescence shows an onset of quenching also around 150 K and disappears completely between 250 and 300 K. For Pr³⁺ quenching of the d-f emission was connected with an increasing intensity of the ³P₀ luminescence at first and ¹D₂ emission at even higher temperatures. Both these 4fⁿ→4fⁿ emissions were observed up to 600 K. Based on the similar quenching temperatures, thermally stimulated photoionization of the 5d electrons from 5d level of Ce³⁺ or Pr³⁺ to the conduction band is proposed as the most probable mechanism for quenching of the d-f emissions.

[en] Radio- and thermoluminescent properties of HfO_2:Ti sintered ceramics were investigated in the temperature range of 10–300 K. Fabrication atmosphere altered somewhat the efficiency of radioluminescence but did not affect the spectral distribution of the broad scintillation band covering the 380–570 nm range of wavelengths and peaking at 522 nm at 10 K and about 490 nm at 300 K. The analogous shift was seen in photoluminescence. Scintillation efficiency was continuously growing from 10 K to 300 K, while photoluminescence intensity was stable in the 10–250 K range of temperatures and was reduced by about 30% at 300 K. Analysis of these observations allowed to conclude that diffusion of carriers generated upon the impact of high-energy photons towards the Ti emitting center is strongly temperature-dependent and inferior at lower temperatures. Upon exposure to X-rays at 10 K the ceramics stored more than 50% of the absorbed energy. This energy could be recovered later upon thermal stimulation of the ceramics. Four main thermoluminescent peaks were then produced at 95, 140, 243 and 278 K. This effect was tentatively associated with theoretically predicted self-trapping of holes in HfO_2. The so-called partial cleaning and T_m_a_x–T_s_t_o_p experiments indicated that some fraction of traps shows a continuous distribution of their depths. - Highlights: • Radio- and thermoluminescence of HfO_2:Ti ceramics within 10–300 K was analyzed. • Energy trapping ability was proved to be independent on the fabrication atmosphere. • Parameters of six traps in HfO_2:Ti ceramics were calculated.