125Te NMR for structural investigations in phase change materials: Optimization of experimental conditions coupled to NMR shift prediction
نویسندگان
چکیده
Phase Change Materials as those of the Ge-Sb-Te ternary system are great interest for technological applications. Properties these compounds strongly related to presence vacancies and structural investigations remain challenging. In this paper we evidence that 125Te NMR in natural abundance using commercial systems at intermediate field (14.1 ?T) together with parameters prediction can contribute improve understanding electronic structure such systems. GeTe is a typical phase change material, whose contains germanium vacancies, even its stoichiometric form, giving it metallic properties. Here, use nominal Ge50Te50 Ge48Te52 crystalline samples an example optimize WURST-CPMG technique, powerful technique record wide spectra which has not yet been used on 125Te. The goal was minimize time devoted experiments well maximize signal-to-noise ratio order detect small intensity signals directly linked vacancies. Virtual Crystal Approximation (VCA) calculations performed WIEN2K helped interpret spectra. For Te-based conducting best experimental results were obtained 3.2 ?mm thin wall rotors diluted 40 ?vol% GeTe-60 SiO2. addition high resolution MAS implemented pj-MAT allowed us identify distributions chemical shift contribution 1D recorded showed Tellurium sample leads important broadening spectrum lines. According VCA could be attributed distribution concentrations would appear Knight Shift but also Chemical similar proportion line position when metavalent bonding invoked.
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ژورنال
عنوان ژورنال: Solid State Nuclear Magnetic Resonance
سال: 2021
ISSN: ['1527-3326', '0926-2040']
DOI: https://doi.org/10.1016/j.ssnmr.2021.101751