Study and modelling of the thermo-mechanical behaviour of melt-textured YBaCuO-composites containing Ag and/or 211 particles

YBa2Cu3Ox high-T-c ceramic super conductors have been elaborated by the mel t-textured-growth method with additions of Ag particles and/or Y2BaCuO5 (21 1 green phase) in order to study the fracture propel ties and the thermal s hock resistance. The Vickers indentation technique, initially devoted to th e sole determination of the toughness has been used in conjunction with a n ew thermal shock resistance parameter. It makes use of the initial stage of stable propagation of Vickers indentation cracks when submitted to a therm al stress, and results in a generalisation of the fourth parameter of Hasse lman. Whereas the toughness increases with increasing 211 content, does the thermal shock resistance decrease. This is explained with respect of the s trongly microcracked (along the 001 planes) microstructure which is seen as a stacking of dense laminates bound by the 211 particles and subjected to a linear temperature gradient. The higher the number of bounding particles, the stiffer the quenched material, and the higher the induced thermal stre ss. This micro-mechanical model is implemented into a finite element softwa re. The first results of the calculations confirm the above approach. (C) 1 999 Elsevier Science Limited. All rights reserved.