Preparation and chemical stability evaluation of new (Nd,An)2Zr2O7-SrZrO3 multiphase ceramics

Abstract

A series of new Nd_(1-x)Sr_xZrO_(3.5–0.5x) (0 ≤ x ≤ 1) multiphase ceramic waste forms, which can simultaneously immobilize An and Sr (with Nd³⁺ simulating An³⁺), were synthesized in situ by a sol-spray pyrolysis method. These multiphase ceramics are composed of a cubic pyrochlore phase Nd₂Zr₂O₇(NZO) and an orthogonal perovskite phase SrZrO₃(SZO) without any impurities. The content of the two phases can change regularly with the change of x. Nd and Sr can occupy the ceramics’ most stable lattice sites. The measured density of multiphase ceramics can reach more than 88% of the theoretical density. At the same time, the leaching rates of target Nd, Sr and Zr elements reached ~ 10⁻⁵ g·m⁻²·d⁻¹, ~ 10⁻³ g·m⁻²·d⁻¹, and ~ 10⁻⁷ g·m⁻²·d⁻¹ at 90 ℃ and deionized water for 72 days, respectively, which shows that the multiphase ceramics had strong leaching resistance. The experimental results confirm that the new multiphase ceramics can immobilize An and Sr simultaneously and separately, and they have high chemical stability and strong adaptability to waste components. The multiphase ceramics is expected to be an ideal candidate waste form for An and Sr.