Topological Origin of the Super‐Flexible Phase of Se and Se‐Rich Glasses and Aging‐Induced 5‐fold Narrowing of Glass Transition Width. Issue 1 (10th November 2021)

• Record Type: Journal Article
• Authors: Chbeir, Ralph; Welton, Aaron; Boolchand, Punit
• Is Part Of: Physica status solidi. Volume 259:Issue 1(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-11-10
• Subjects: aging of glasses -- chalcogenide glasses -- modulated differential scanning calorimetry -- Raman scattering -- topological constraint theory; Solid state physics -- Periodicals; Solids -- Periodicals; Atomic structure -- Periodicals; 530.41
• DOI: 10.1002/pssb.202100400
• Languages: English
• ISSNs: 0370-1972

Abstract

Abstract : Pure Se glass and ternary A x B y Se1− x − y glasses where A = Ge and B = P or As, in the low mean coordination number, ⟨ r ⟩, range of 2.00 < ⟨ r ⟩ < 2.12 display a 3‐ to 5‐fold reduction in the width of the glass transition when aged at room temperature over 4–8 months. Group IV (Ge) and group V (P, As) additives serve to crosslink the base Se glass polymeric chains, Se n, with n > 250 atoms and to reduce the length " n " between cross‐link points as x and y are increased. Herein, it is shown that in such weakly crosslinked glasses, the continued narrowing of the glass transition width T g by a factor of 3–5, as in pure Se, stems from the fact that polymeric Se n chain segments between the crosslink points continue to have a length n of at least eight atoms or more. Such polymeric Se n chains are super‐flexible and reconstruct with each, as in pure Se, promoting structural ordering responsible for T g narrowing. When n < 8, super flexibility is steadily lost. Along with the flexible, intermediate, and stressed‐rigid phases, a new super‐flexible phase of Se and Se‐rich glasses is obtained. Abstract : Pure Se and Se‐rich glasses can exist in a new topological phase called the super‐flexible phase. In this phase, polymeric Se n chains exist in the 250 > n > 8 length range. Glass transition widths of such glasses can narrow by a factor of 3–5 upon room temperature aging for 4 months as the long Se n chains reconstruct.