Failure mode, ferroelastic behavior and toughening effect of bismuth titanate ferroelectric ceramics under uniaxial compression load

Publication date: 15 August 2018
Source:Materials & Design, Volume 152
Author(s): Yu Chen, Jiageng Xu, Shaoxiong Xie, Rui Nie, Jing Yuan, Qingyuan Wang, Jianguo Zhu
A typic BLSF ceramics: bismuth titanate (Bi4Ti3O12), whose failure mode, ferroelastic behavior and toughening effect under uniaxial compression load were comprehensively assessed. Firstly, a series of crystallographic parameters including lattice constants (a, b, c and v), orthorhombicity (g) and single-crystal distortion (S⁰lattice) were calculated from XRD patterns. The ferroelastic behavior referred to the 90° switching of domains with compression stress was identified by the nonlinear stress-strain curve, and the underlying micromechanism was more accurately described by the non-180° domain wall motion. SEM observation on the fracture surface of the broken sample reveals its failure mode in terms of microcrack initiation and propagation behaviors. Further, a simplified domain distribution model was constructed for unpoled ferroelectric ceramics based on a constitutive framework, which deduced their constitutive relation subjected to uniaxial compression load. The ferroelasticity induced toughening was verified by indentation test, and further analyzed by a micromechanics model of crack propagation. The expression of toughening effect (ΔГ/Г) was also deduced from the indentation fracture mechanics. Finally, the evolution in mechanical properties (including coercive stress (σc), switching strain (εzz), apparent elastic modulus (E) and compression strength (σcf)) of Bi4Ti3O12 ceramics with the doping content of W was also quantified by the compression test.

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