Synchrotron x-ray diffraction studies of the $\alpha \rightleftharpoons \beta$ structural phase transition in Sn and Sn-Cu

TL;DR

This study investigates the alpha-beta phase transition in tin and tin-copper alloys using synchrotron x-ray diffraction, revealing insights into transition temperatures and proposing methods to control phase formation for detector applications.

Contribution

It provides new temperature-resolved diffraction data and a protocol to minimize alpha-tin formation, improving understanding of tin's phase transition relevant to detector technology.

Findings

Transition temperature discrepancies clarified

Alloying with copper affects phase stability

Proposed protocol reduces alpha-tin formation

Abstract

The transformation between the metallic ($\beta$) and semi-conducting ($\alpha$) allotropes of tin is still not well understood. The phase transition temperature stated in the literature, 286.2 K, seems to be inconsistent with recent calorimetric measurements. In this paper, this intriguing aspect has been explored in Sn and Sn-Cu (alloyed 0.5% Cu by weight) using temperature resolved synchrotron x-ray diffraction measurements performed at the Indus-2 facility. Additionally, the $\alpha \rightleftharpoons \beta$ Sn transition has been recorded using in-situ heating/cooling experiments in a scanning electron microscope. Based on these measurements, a protocol has been suggested to reduce the formation of $\alpha$-Sn in potentially susceptible systems. This will be useful in experiments like TIN.TIN (The INdia-based TIN detector), which proposes to employ ~100 - 1000 kg of superconducting tin-based detectors to search for neutrinoless double beta decay in the isotope $^{124}$Sn.