Synthesis of Nd3BSi2O10 using a LiCl-flux method

Abstract This paper details synthesis methods that were used to fabricate phase-pure Nd 3 BSi 2 O 10 using a LiCl-flux method. In this study, a variety of conditions were evaluated to find the optimal processing parameters for maximizing the Nd 3 BSi 2 O 10 yield including the mass ratio of LiCl to target mass of Nd 3 BSi 2 O 10 (i.e., 1:3, 1:2, 1:1, 2:1, and 6:1) as well as the soak temperature (i.e., 700, 800, or 900 °C) at the 1:1 ratio. It was found that the optimal ratio of LiCl:Nd 3 BSi 2 O 10 was 1:1 and the optimal heat-treatment temperature was 900 °C (of those temperatures evaluated). Product made from the 1:1 material synthesized at 900 °C was recovered and fired at temperatures of 925–1350 °C. After 4-h firings at temperatures of 925–1100 °C, the Nd 3 BSi 2 O 10 phase purity was found to be 100% with powder X-ray diffraction, but started to decompose at the longer firing times at 1100 °C and higher temperatures (1350 °C) at the 4-h dwell time. Thus, the lowest firing temperature for achieving a phase-pure pellet was 925 °C under the conditions studied here. The phase-pure sample was found to contain 28 vol% open porosity determined by Archimedes’ method. The durability of the Nd 3 BSi 2 O 10 product was examined in flow-through conditions at 90 °C with contacting solution between pH 90oC 4.1 and 10.1. The release rate of Nd from the material had a maximum at pH 90oC 4.1 calculated to be 4.93 g m −2  d −1 and a minimum release rate of Nd at pH 90oC 7.7 of −5  g m −2  d −1 . These release rates are roughly three orders of magnitude lower than what is normally measured from typical glass waste forms at pHs of 7–9.