Fracture behavior of electronic ceramics

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Abstract
This paper reviews the fracture behavior, e.g., the strength, fracture toughness and susceptibility to environmentally enhanced crack growth, in electronic materials such as barium titanate, lead zirconate titanate (PZT), capacitor ceramics, and the new, high temperature superconductors. All of these materials are known to exhibit critical fracture toughness, KIC , which depends on grain size, chemical composition and crystal structure. The microstructure of these electronic ceramics has a direct effect on both their strength and fracture toughness. The paraelectric to ferroelectric phase transformation in barium titanate, PZT, and related ceramics induces internal stresses into the materials which can provide an additional driving force for flaw extension. The magnitude of such stresses calculated from strength data is in good agreement with that predicted by dielectric measurements. Crack-domain interactions in the ferroelectric structure as well as crack deflection, etc. give rise to increased fracture toughness. Finally, crack growth rates in these materials have been shown to be accelerated by the presence of moisture in the environment, which can significantly increase the probability of failure.