Stuctural 2D and 3D data for a ceramic Gd0.96Eu0.01Sm0.01Tb0.01Er0.01NbO4 sample

Description

The ceramic sample was prepared from a fine powder of the composition Gd0.96Eu0.01Sm0.01Tb0.01Er0.01NbO4, synthesized by the liquid-phase method using nitrate solutions of rare earth elements and niobium hydroxides, which was described in detail in [10.3390/ceramics5030038]. The hydrated sediment was washed with deionized water at a ratio of solid and liquid phases T:Vl = 1:3, dried at ~ 150°C, and then calcined at a temperature of ~ 1000°C for 3 hours. The consolidation of Gd0.96Eu0.01Sm0.01Tb0.01Er0.01NbO4 powder was carried out by the SPS (spark plasma sintering) method on an SPS-515S installation from Dr.Sinter LABTM (Japan), according to the general approach: 2 g of powder was placed in a graphite mold (working diameter 12.5 mm), was pressed (pressure 20.7 MPa), then the workpiece was placed in a vacuum chamber (10-5 atm), then sintered. Heating of the sintered material was carried out with a unipolar low-voltage pulsed current in the On/Off mode, with a frequency of 12 pulses / 2 pauses, i.e. the duration of the pulse packet was 39.6 ms and the pause was 6.6 ms. The SPS process temperature was controlled using an optical pyrometer (lower limit of determination 650 °C) focused on a hole located in the middle of the plane of the outer wall of the mold with a depth of 5.5 mm. To prevent the consolidated powder from sticking to the mold and plungers, as well as to unhindered removal of the resulting sample, graphite foil 200 μm thick was used. The mold was wrapped in heat-insulating fabric to reduce heat loss during heating. Geometric dimensions of the obtained ceramic samples: diameter 12.5, height 2.5-3 mm. SPS consolidation of powders was carried out at a temperature of 1200°C, the heating rate was controlled in stages: 300°C/min in the temperature range from 0 to 650°C, then from 650°C and higher (working area of ​​the pyrometer) – 100°C/min. The sample was kept at maximum temperature for 5 min and then cooled to room temperature over 30 min. The compaction pressure during consolidation was 37 MPa. The sample diameter was 10 mm, thickness 2 mm. A 3D tomogram of the sample was obtained on an X3000 instrument (North Star Imaging, Inc.). shooting parameters for the sample in Fig. 2a: detector pixel pitch 0.127x0.127 mm, distance between the X-ray source and detector - 697.808 mm, optimal voxel size - 76.9 µm, image magnification - 1.65, type of shooting - step, ring reduction, number of projections - 1600, size of projection images -1514 x 1825, voltage between the X-ray electrodes tubes - 210 kV, emitter current - 270 µA. For the sample from Fig. 2 b: detector pixel pitch 0.127x0.127 mm, distance between the X-ray source and detector - 788.785 mm, optimal voxel size - 82 µm, image magnification - x1.55, shooting type - step, ring reduction, number of projections -1700, size of projection images - 1514 x 1825, voltage between the X-ray tube electrodes - 205 kV, emitter current - 270 µA. A copper filter with a thickness of 1 mm was used.

Institutions

• Kola Science Centre

  Murmansk, Apatity

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