Abstract

Purpose. The purpose of this work is the investigation of mechanical characteristics of superoinic crystals Cu₆PS₅Br(І) and Cu₆PS₅І-based thin films deposited and to determine of indentation size effects.
Methods. The measurements of hardness H and Young's modulus E were performed using a CSM Instruments NHT-TTX nanohardness meter at a temperature of 293 K. The measurements of mikrohardness were performed using a PMT-3 mikrohardness meter with Vickers pyramid.
Results. The nanohardness and Young's modulus of Cu₆PS₅Br(І) crystals and films were measured by nanoindentation method with harmonic modulation force. In dependences H(h) and E(h) reveal features that indicate a significant change in mechanical characteristics of crystals in the nanoregion. Obtained dependences have been approximated in the framework of strain gradient plasticity theory. The mechanical parameters of Cu₆PS₅І films have been studied depending on the penetration depth of indenter during nanoindentationt. The effect of the influence substrate on the interaction between a film and indenter in nanocontact region is shown.
Conclusions. It is shown that deformation of Cu₆PS₅Br(І) crystals in a nano-region is mostly elastic and can be interpreted in Hertz's theory. The plastic deformation of crystals in the micro-region has a dislocation mechanism. The dimensional effects are explained within the framework of strain gradient plasticity theories. Dimensional effects are due to the formation during the indentation of circular loops of geometrically necessary dislocations with Burgers vectors perpendicular to the plane surface of the crystal. The reduction in the microhardness of Cu₆PS₅І-based thin with increasing copper content is due to structure

Keywords: nano- and micro-indentation, superionic materials, Cu6PS5Br(І), dislocations; hardness; indentation size effects, Stress-Gradient Plasticity Model

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