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Na x Sr 1 -2x Nd x MoO 4 (x = 0-0.5, Δx = 0.1) solid solutions with the scheelite structure have been synthesized for the first time and their crystallographic parameters have been determined as functions of composition and temperature. Their thermal expansion coefficients have been determined in the temperature range 25-1000°C: α a = (12.9-14.9) × 10 -6 °C -1 and α c = (24.9-25.9) × 10 -6 °C -1 . Using spark plasma sintering at t max ≈ 872-985°C and τ ≈ 650-750 s, we have prepared ceramics with relative densities in the range 97-99%.

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This paper reports on the preparation of xenotime-structured ceramics using the Spark Plasma Sintering (SPS) method. Y0.95Gd0.05PO4 (YPO4:Gd) phosphates were obtained using the sol-gel method. The synthesized powders were nanodispersed and were agglomerated (the agglomerates sizes were 10–50 µm). The ceramics had a fine-grained microstructure and a high relative density (98.67 ± 0.18%). The total time of the SPS process was approximately 18 min. The sintered high-density YPO4:Gd ceramics with a xenotime structure were irradiated with 132Xe+26 ions with 167 MeV of energy and fluences in the range of 1 × 1012–3 × 1013 cm−2. Complete amorphization was not achieved even at the maximum fluence. The calculated value of the critical fluence was (9.2 ± 0.1) × 1014 cm−2. According to the results of grazing incidence X-ray diffraction (GIXRD), the volume fraction of the amorphous structure increased from 20 to 70% with increasing fluence from 1 × 1012 up to 3 × 1013 cm−2. The intensity of the 200 YPO4:Gd XRD peak reached ~80% of the initial intensity after recovery annealing (700 °C, 18 h).