Fabrication, characterization, and acid solubility of MgO-Nd2Zr2O7 composite ceramics for inert matrix fuel

In the present paper, the ordered Nd 2 Zr 2 O 7 pyrochlore was primarily synthesized by flux method and the MgO-Nd 2 Zr 2 O 7 composite ceramics were fabricated subsequently through a conventional sintering route. A suite of characterization techniques, including XRD, Raman and BSE-EDS were employed to investigate the phase composition and microstructure of the as-prepared Nd 2 Zr 2 O 7 and MgO-Nd 2 Zr 2 O 7 samples. The acid solubility of the MgO-Nd 2 Zr 2 O 7 composite ceramics was also tested. XRD results showed that the ordered Nd 2 Zr 2 O 7 pyrochlore can be synthesized when the calcination temperature is in the range of 850–1200 °C. Raman results suggested that the chemical bonds of Nd 2 Zr 2 O 7 pyrochlore get stronger, and more ordered structure can be gradually formed with the increase of calcining temperature. For the MgO-Nd 2 Zr 2 O 7 composite ceramics, XRD results also showed that the Nd 2 Zr 2 O 7 phase in the composite ceramics presents higher crystallinity degree and no other phase is formed after sintering at 1400–1550 °C. Moreover, BSE-EDS results indicated that the MgO-Nd 2 Zr 2 O 7 composite ceramics are compact and dense, and the MgO and Nd 2 Zr 2 O 7 phases are almost uniformly distributed between each other. In addition, the relative density of the bulk ceramics was about 96–98%, and it was concluded that ≥ 1500 °C could be the suitable sintering temperature to produce MgO-Nd 2 Zr 2 O 7 composite ceramics. At last, the dissolution behavior of the ceramics in nitric acid solution revealed that only MgO in the MgO-Nd 2 Zr 2 O 7 composite ceramics can be dissolved in the 11 M HNO 3 solution within 24 h, and the dissolution rate was relatively low because of the high densification of the sample.