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The paper studies ceramic samples prepared using traditional ceramic technology also knows as conventional sintering. Samples were prepared from Eu3+ activated fine powders of gadolinium niobate-tantalates GdNb1−yTayO4 (y = 0, 0.7, 1); Eu3+ concentration was x = 0.01, 0.2 and 0.4. Powders were synthesized using nitrate solutions Gd and Eu and niobium and tantalum hydroxides. The hydroxides were coprecipitated from hydrofluoric acid solutions. Full-profile analysis (Rietveld refinement) of XRD (X-ray diffraction) patterns of polycrystals determined the phase composition and refined the parameters of the structure of solid solution phases depending on the Eu concentration. Morphological features of the microstructure have been studied for gadolinium niobate-tantalate ceramics Gd1−xEuxNb1−yTayO4 where y = 0, 0.7, 1 and x = 0.01, 0.2, 0.4. Their mechanical properties have been studied; strength characteristics (Young's modulus, microhardness) and critical stress intensity factor for mode I KIC have been estimated. The compositions and modes for producing ceramics with optimal mechanical properties have been determined. The photoluminescence (PL) has been studied in ceramic solid solutions in the visible range upon excitation by near UV (376 nm). The features of energy transfer between the host of ceramic GdNb1−yTayO4:Eu solid solution (y = 0; 0.7; 1) and 4fn-4fn levels of Eu in concentrations x = 0.01, 0.2 and 0.4 have been established. We have established that concentration quenching of PL in single-phase ceramics Gd1−xEuxNbO4 occurs above Eu concentration x > 0.01 and in ceramics Gd1−xEuxTaO4—at Eu concentration x > 0.2. The sample with the composition Gd0.99Eu0.01NbO4 demonstrated the maximal PL intensity among all other studied samples. The least PL intensity is observed in Gd0.99Eu0.01Nb0.3Ta0.7O4 relative to individual compounds of gadolinium niobates and tantalates, activated with Eu in the same concentration x = 0.01. The significant difference in Stark splitting of levels has been shown for solid solutions based on niobium (Gd1−xEuxNbO4) and tantalum (Gd1−xEuxTaO4). The compositions of ceramic GdNb1−yTayO4:Eu solid solution have been established which have maximum luminance. We have determined that the luminance of some of the studied samples exceeded the luminance of an industrial phosphor based on Y2O3:Eu3+. [ABSTRACT FROM AUTHOR]

SiC-TiB2 composite ceramics of the solid-state has stable property in high temperature with wide application. In the paper, SiC-TiB2 composite ceramics was prepared by spark plasma sintering with 50 MPa pressure and heat preservation for 10 min at 1750 ℃, and the effect of TiB2 content (0 vo l%-20 vol%) on microstructure and mechanical properties of SiC composite ceramics by solid-state spark plasma sintering was investigated. The experimental results show that the grain growth of SiC is inhibited with the increase of TiB2 content. When TiB2 content is 20 vol%, TiB2 promotes the decomposition of SiC into Si, which is located in the grain boundaries of SiC and TiB2 to reduce mechanical properties of composite ceramics. SiC-15 vo l%TiB2 composite ceramics have the preferable comprehensive mechanical properties with relative density, Vickers hardness, bending strength and fracture toughness of 98.8%, 27.2 GPa, 431 MPa and 5.24 MPa • m1/2, respectively. [ABSTRACT FROM AUTHOR]