Janek, M; Cickan, M; Klement, R; Matejdes, M; Furka, D; Furka, S; Baca, L; Naftaly, M (2024) Temperature dependent terahertz spectroscopy study of rare earth modified smectites: Probing the structural responses. Applied Clay Science, 255. 107406

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Abstract

Selected layered clay minerals of smectite group with different chemical composition (e.g. synthetic hectorite, synthetic smectite and natural smectite) were modified by rare earth cations such as Er3+ and a stochiometric mixture of Er3+/Yb3+. Raw and modified smectites were systematically heated up to temperatures ensuring their dehydration (400 ºC), dehydroxylation (800 ºC) and formation of new high temperature phases (1200 ºC). The products of heating were investigated by terahertz-time domain spectroscopy to follow changes of their dielectric properties in the far-infrared region. The frequency-dependent refractive index of raw and modified clays was determined in the range of 0.2–3.8 THz (6.6–126.5 cm -1). The heating at 800 ºC and above resulted in increase frequency dependent index of refraction and decrease absorption coefficient in comparison to the raw clays. The ion-exchanged smectites by rare earth cations further decreased the absorption coefficient of the samples heated at 1200 ºC. Raw natural smectite sample revealed a low frequency band at 0.86 THz, already reported in the literature, which shifted to 0.67 THz after sample modification by rare earth cations. Heating of modified JP to 1200 ºC resolved a new absorption band at ~3.40 THz in the ceramic phase produced from raw natural smectite.

Item Type:	Article
Keywords:	terahertz, materials
Subjects:	Electromagnetics > Terahertz
Divisions:	Electromagnetic & Electrochemical Technologies
Identification number/DOI:	10.1016/j.clay.2024.107406
Last Modified:	18 Sep 2024 10:42
URI:	https://eprintspublications.npl.co.uk/id/eprint/10028