Depth-Sensing Indentation on REBa2Cu3O7−δ Single Crystals Obtained from Xenotime Mineral

• Published in: Brazilian journal of physics Vol. 42; no. 5-6; pp. 330 - 339
• Main Authors: Serbena, Francisco Carlos, Foerster, Carlos Eugênio, Jurelo, Alcione Roberto, Mikowski, Alexandre, Júnior, Pedro Rodrigues, Carubelli, Célia Regina, Lepienski, Carlos Maurício
• Format: Journal Article
• Language: English
• Published: New York Springer-Verlag 01.12.2012
• Subjects: Condensed Matter; Physics; Physics and Astronomy; Mechanical properties; High-temperature superconductors; Single crystal; Xenotime
• ISSN: 0103-9733; 1678-4448
• DOI: 10.1007/s13538-012-0088-8

A natural mixture of heavy rare-earth oxides extracted from xenotime mineral have been used to prepare large single crystals of the high-temperature REBa 2 Cu 3 O 7−δ superconductor, grown using the CuO–BaO self-flux method. Its mechanical properties along the ab -plane were characterized using instrumented indentation. Hardness and elastic moduli were measured by the Oliver and Pharr method, which yielded 7.4 ± 0.2 GPa and the range 135–175 GPa at small depths, respectively. Increased loads promote the nucleation of lateral cracks, which reduce hardness and measured elastic modulus, as indicated by instrumented indentation at higher loads. The indentation fracture toughness, estimated by measuring the radial crack length from cube corner indentations at various loads, was found to be 0.8 ± 0.2 MPa m 1/2 . The observed slip systems of REBa 2 Cu 3 O 7−δ single crystals were [100](001) and [010](001), the same as for YBa 2 Cu 3 O 7−δ single crystals. The initial stages of deformation and fracture in the indentation process were investigated. The hardness and elastic modulus are not strongly modified by the crystallographic orientation in the ab -plane. This was interpreted in terms of resolved shear stresses in the active slip systems. Evidence of cracking along the {100} and {110} planes on the ab -plane was observed. In conclusion, the mechanical properties of REBa 2 Cu 3 O 7−δ single crystals prepared from xenotime are equivalent to those of YBa 2 Cu 3 O 7−δ single crystals from conventional rare-earth oxides.