| In this thesis, combined effects of stress, electric field and environment on domain switching and crack propagating for ferroelectric materials such as PZT ceramics and BaTiO3 single crystal have been studied. For example, the combined effect of applied stress and electric field on crack propagation has been investigated using Vickers indentation crack. The influence of environment such as humid air on domain switching of BaTiO3 single crystal has been studied. Stress corrosion cracking of BaTiO3 single crystal in humid air and water and its relationship to domain switching have been studied using indentation crack and penetrating crack. The main conclusions obtained in this thesis are as follows: 1. Either positive or negative electric field can generate a tensile internal stress σin along the field and causes propagating of crack normal to the field; the effect of the field and applied stress on propagation of indentation crack is linear addition and no synergistic action. 2. Humid air can enhance domain switching from a domain to c domain under constant electric field, but resist that from c domain to a domain, which is due to anisotropy of adsorption-decreased surface energy. 3. Humid air can promote domain switching and causes stress corrosion cracking under constant deflection, and the domain switching ahead of crack tip is a precondition for crack propagation under stress corrosion cracking.
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