Diverse Thermal Expansion Behaviors in Ferromagnetic Cr<sub>1−δ</sub>Te with NiAs-Type, Defective Structures
Chen Li, Ke Liu, Dequan Jiang, Cheng Jin, Tianyao Pei, Ting Bin Wen, Binbin Yue, Yonggang Wang
Abstract
Negative thermal expansion (NTE) and zero thermal expansion (ZTE) properties are of great significance for the long-life stable operation of precision equipment. However, there are still existing challenges in finding new materials that exhibit NTE or ZTE over a wide temperature range. Here, we report negative, zero, and positive thermal expansion in NiAs-type, defective Cr1−δTe, containing three compounds: hexagonal CrTe, monoclinic Cr3Te4, and trigonal Cr5Te8. CrTe shows the NTE behavior from 280 to 340 K with the volume coefficient of thermal expansion αV = −27.6 × 10–6 K–1. Cr3Te4 shows the ZTE behavior over a wide temperature range of 180–320 K (αV = 0.16 × 10–6 K–1). And Cr5Te8 holds the PTE behavior over the whole temperature range (αV = 38.5 × 10–6 K–1). All of the samples show obvious anisotropic thermal expansion on heating. Combined with the magnetic measurements, it can be confirmed that the NTE and ZTE properties in ferromagnetic Cr1−δTe originate from the magnetovolume effect (MVE). Such NiAs-type, defective compounds with similar compositions but different structures provide a new perspective for tuning the NTE properties of materials and searching for new materials with ZTE over a wide temperature range.