Fabrication and phase transition of uranium-doped LaxGd2-xZr2O7 transparent ceramics: A prospective neutron detection material

Via vacuum sintering, 2 mol% uranium-doped LaxGd2-xZr2O7 (x = 2, 1.6, 1, and 0.4) transparent ceramics with Ca2+ as charge compensator was first fabricated by solid-state reaction. X-ray diffraction results of as-prepared powders and ceramic samples demonstrate that the phase transition from defective fluorite to pyrochlore occurs with the increase of x. Optical in-line transmittance spectrum shows that four ceramic samples have good in-line transmittance (nearly 80% from 700 to 2200 nm), especially the U:La1.6Gd0.4Zr2O7 ceramics. The cut-off wavelength of four U-doped transparent ceramics shifted from 250 to near 460 nm, and it is believed that such phenomenon is related to the stable existence form of uranium in ceramics lattices. Observing the excitation emission spectra, the main excitation peaks of four ceramic samples are located at 458 nm, and the main emission peaks are located around 513 nm. In addition, there are low-intensity emission peaks around 520, 537, and 566 nm, and the related explanation is given in combination with the U6+ ion energy level diagram. Thus, uranium-doped LaxGd2-xZr2O7 transparent ceramics have potential for novel neutron detection materials.