Development of a New Sr-O Parameterization to Describe the Influence of SrO on Iron-Phosphate Glass Structural Properties Using Molecular Dynamics Simulations.

Pawel Goj,Pawel Stoch,Aleksandra Wajda

doi:10.3390/ma14154326

Abstract

Iron-phosphate glasses, due to their properties, have many potential applications. One of the most promising seems to be nuclear waste immobilization. Radioactive 90Sr isotope is the main short-lived product of fission and, due to its high solubility, it can enter groundwater and pose a threat to the environment. On the other hand, Sr is an important element in hard tissue metabolic processes, and phosphate glasses containing Sr are considered bioactive. This study investigated the effect of SrO addition on a glass structure of nominal 30Fe2O3-70P2O5 chemical composition using classical molecular dynamics simulations. To describe the interaction between Sr-O ion pairs, new interatomic potential parameters of the Buckingham-type were developed and tested for crystalline compounds. The short-range structure of the simulated glasses is presented and is in agreement with previous experimental and theoretical studies. The simulations showed that an increase in SrO content in the glass led to phosphate network depolymerization. Analysis demonstrated that the non-network oxygen did not take part in the phosphate network depolymerization. Furthermore, strontium aggregation in the glass structure was observed to lead to the non-homogeneity of the glass network. It was demonstrated that Sr ions prefer to locate near to Fe(II), which may induce crystallization of strontium phosphates with divalent iron.

Highlights

Phosphate glasses are an important group of materials that possess many interesting features
The glass density increased according to the formula ρ(x) = 1.5·10−4 x2 + 0.0856x
The increase of SrO content led to an increase of the regions and, in this way, the whole glass network became more homogenous

Summary

Introduction

Phosphate glasses are an important group of materials that possess many interesting features. Their properties mean that they can be applied in many different fields. The existence of hydrated P-O-P bridges leads to their corrosion, induced by water originating, for example, in a humid environment [10,11]. This effect may limit such glasses’ potential applications. A superior water-resistant material can be obtained and the glasses can be considered as matrixes in the waste immobilization process [12,13]. One of the most promising materials for this purpose is glass of the composition 60P2 O5 -40Fe2 O3 [12,13,14]

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