Synthesis, crystal structure and properties of YB₂C₂

ABSTRACT

YB₂C₂ is a novel ultra-high temperature ceramic material with high damage tolerance. In this work, the synthesis mechanism, crystal structure, electronic structure, elastic properties and thermal shock resistance of YB₂C₂ were systematically investigated through experiments and calculations. It was determined by differential scanning calorimetry with the heating rate of 10°C/min that YB₂C₂ was formed by the reaction of YB₂C and C at about 1202°C, and became the main phase at 1450°C. The space group of YB₂C₂ was determined to be P4/mbm by X-ray diffraction, transmission electron microscopy, Rietveld refinement and first-principles calculations for the first time. The lattice constants are a = b = 0.5351 nm and c = 0.3561 nm. The atom positions are as follows: Y is located at 2a (0, 0, 0), B is located 4 h (0.133, 0.633, 0.5) and C is located at 4 h (0.662, 0.162, 0.5). The chemical bonding of YB₂C₂ displayed sharp anisotropy, with strong B-C bond within the B₂C₂ nets, and weak Y-B/Y-C bond between Y atom layers and B₂C₂ nets. Additionally, YB₂C₂ exhibited abnormal thermal shock resistance when the thermal shock temperature exceeded 800°C, with the residual flexural strength at 1300°C being more than 70% of the strength at room temperature.

KEYWORDS:

• YB₂C₂
• synthesis mechanism
• crystal structure
• properties

Disclosure statement

The author(s) declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Additional information

Funding

This work was supported by the Guangdong Major Project of Basic and Applied Basic Research (2021B0301030002), the National Natural Science Foundation of China (Nos. 52101091 and 52032011), the Guangdong Basic and Applied Basic Research Foundation (Nos. 2021B1515140061), Dongguan Sci-tech Commissioner Program (20221800500592), SSL Sci-tech Commissioner Program (20234374-01KCJ-G), the Start-up Funding support from Songshan Lake Materials Laboratory (Y2D1041C711) and the National Key Research and Development Program of China (2022YFA1403500 and 2022YFC2403702).