This paper discusses the characteristics of ZnO and ZnO:Ga ceramics fabricated by uniaxial hot pressing. The short-wavelength transmission limit of zinc oxide ceramics is in the 370-nm region; the long-wavelength limit is determined by the free-charge-carrier concentration and lies in the interval from 5 to 9 μm. The total transmittance of such ceramics in the visible and near-IR regions is about 70% when the sample is 0.5 mm thick. The luminescence spectrum is represented by a broad emission band with maximum at 580 nm, having a defect nature. The introduction of 0.03-0.1 mass % gallium into the zinc oxide structure inhibits grain growth and increases the free-charge-carrier concentration to 3.44 × 10 19 cm −3. As the gallium concentration increases in the range 0.05-0.1 mass % in a ceramic of composition ZnO:Ga, the defect luminescence band is suppressed and a characteristic exciton luminescence is formed with a maximum corresponding to 389 nm and a damping time constant of 1.1 ns.

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This paper discusses the structural, optical, and spectrokinetic characteristics of ceramics based on gadolinium oxysulfide Gd 2 O 2 S:RE (RE = Pr, Tb, Eu), obtained by the method of uniaxial hot pressing. It is shown that the composition and conditions of hot pressing affect the parameters of the Gd 2 O 2 S lattice and the formation of the predominant grain orientation in the (001) plane of the pinacoid. All the ceramics possess transparency that is high for an anisotropic material (about 40% at a thickness of 1.65 mm) in the intrinsic emission region. The overall x-ray luminescence intensities (relative to CsI:Tl) for the Gd 2 O 2 S:Pr,Ce, Gd 2 O 2 S:Tb(Ce), and Gd 2 O 2 S:Eu ceramics are 50, 160 (120), and 200%, respectively, while the damping time constants are 3.2, 600-700, and 450 µs, respectively.The high density (7.34 g/cm 3 ), relatively small band gap (4.3 eV), and conformity to the requirements on absorption in a wide range of energies of gadolinium oxysulfide (Gd 2 O 2 S), make it promising for use in modern devices of x-ray medical engineering as a matrix for obtaining a scintillation material. Doping this matrix with ions having variable valence, Eu 2+,3+ , Tb 3+,4+ , and Pr 3+,4+ , and possessing a large damping cross section (>10 −14 cm 2 ) ensures a high conversion efficiency of the phosphors, as well as making it possible to vary the spectral composition and radiationdamping time. Powdered phosphors based on Gd 2 O 2 S doped with these elements have been widely used for a long time to record x-ray, UV, and electron radiation, and this explains why their characteristics have been studied fairly deeply. The situation is different for studies of single-crystal and optical polycrystalline-ceramic scintillation materials. There is virtually no information on the former because of problems in obtaining single crystals of Gd 2 O 2 S. As far as ceramic materials are concerned, the scintillation characteristics of Gd 2 O 2 S:Pr,Ce ceramics, which are being actively used in detectors for computerized tomography, have been studied in the greatest detail. 1 This paper presents a review of data based on x-ray structural analysis and the study of the microstructure and transparency of Gd 2 O 2 S:RE ceramics (RE = Pr, Tb, Eu) and obtained by investigating its spectrokinetic characteristics. 2-4 EXPERIMENTAL TECHNIQUEThe process of uniaxial hot pressing (HP) of the samples was carried out in high-temperature vacuum furnaces. The original powders used in this paper, a characteristic image of which is shown in Fig. 1(a), had a grain size of 3-7 µm. The concentration of the dopants (Pr 3+ , Tb 3+ , Eu 3+ ) fluctuated within the limits 0.08-1.0 mass%, and the Ce 3+ concentration was 0.002 mass%. Since Gd 2 O 2 S is a refractory compound (T m ≈ 2250 • C), to achieve high density and transparency of the ceramic, the pressing process was carried out in the presence of an easily melted fluorine-containing additive, which simultaneously served the function of supplying the F − ion needed to obtain the required luminesce...

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