AUTHOR=Sreenivasan Harisankar , Kinnunen Paivo , Adesanya Elijah , Patanen Minna , Kantola Anu M. , Telkki Ville-Veikko , Huttula Marko , Cao Wei , Provis John L. , Illikainen Mirja 

TITLE=Field Strength of Network-Modifying Cation Dictates the Structure of (Na-Mg) Aluminosilicate Glasses

JOURNAL=Frontiers in Materials

VOLUME=7

YEAR=2020

URL=https://www.frontiersin.org/journals/materials/articles/10.3389/fmats.2020.00267

DOI=10.3389/fmats.2020.00267

ISSN=2296-8016

ABSTRACT=<p>Aluminosilicate glasses are materials with a wide range of technological applications. The field strength of network-modifying cations strongly influences the structure of aluminosilicate glasses and their suitability for various applications. In this work, we study the influence of the field strength of network-modifying cations on the structure of [(Na<sub>2</sub>O)<sub>1–x</sub>(MgO)<sub>x</sub>(Al<sub>2</sub>O<sub>3</sub>)<sub>0</sub>.<sub>25</sub>(SiO<sub>2</sub>)<sub>1</sub>.<sub>25</sub>] glasses. Due to the higher cation field strength of magnesium than sodium, magnesium prefers the role of network modifier, while sodium preferentially acts as a charge compensator. When magnesium replaces sodium as network modifier, Q<sup>3</sup> silicon species are converted into Q<sup>2</sup> species. The replacement of sodium with magnesium as charge compensator leads to the following changes: (1) the proportion of aluminum-rich Q<sup>4</sup> species [Q<sup>4</sup>(4Al) and Q<sup>4</sup>(3Al)] decreases, while the proportion of aluminum-deficient Q<sup>4</sup> species [Q<sup>4</sup>(2Al) and Q<sup>4</sup>(1Al)] increases; and (2) there is an increased tendency for phase separation between silica-rich and alumina-rich glasses.</p>