Investigations on structure and optical properties of neutron irradiated nanocrystalline La2Zr2O7 pyrochlores

Abstract

This research work investigates the response of nanocrystalline lanthanum zirconium oxide (LZO) under neutron irradiation, emphasizing grain size-dependent structural stability. LZO samples were synthesized with the chemical precipitation method and the LZO pellets were annealed at two different temperatures (1200 °C and 1400 °C) to obtain two different grain size samples, namely LZO-1200 and LZO-1400. The samples were exposed to neutrons at different doses (ranging from 1.63 × 1012 n/cm2 to 5.68 × 1014 n/cm2) and the effects were studied with X-ray diffraction, scanning electron microscopy, Raman scattering and optical characterization. The structural characterization results reveal that, the grain size and strain are significantly modified in LZO-1400 samples, and such changes are absent inLZO-1200 samples. The band gap and photoluminescence intensity are reduced significantly in LZO-1400 samples, however, this effect is not observed in LZO-1200 samples. The experimental results reveal that in LZO-1200 samples, the grain boundaries act as a sink for irradiation-induced defects and there is no significant change in the grain size, strain and band gap. However, in the case of the LZO-1400 sample, the grain size is larger than the cascades induced by primary knock-on atoms (PKAs) and it results in disorder-driven fast grain growth and changes in band gap and PL intensity. The LZO-1200 samples with small grain sizes are radiation resistant.