电场对不同极化状态PZT-5H铁电陶瓷断裂韧性的影响

EFFECT OF VARIOUS ELECTRIC FIELDS ON FRACTURE TOUGHNESS OF A PZT5H FERROELECTRIC CERAMIC IN VARIOUS POLING STATES

用缺口拉伸试样研究了未极化、沿长度和厚度极化的PZT5H铁电陶瓷表观断裂韧性随各种外加电场的变化。结果表明在各种情况下,表观断裂韧性都随外电场的增加而线性降低。力、电耦合下的断裂判据为KⅠ(σ)+KⅠ(E)=KⅠc,其中KIc为断裂韧性,KⅠ(σ)和KⅠ(E)分别为应力σ和电场E引起的应力强度因子。KI(E)=ψYE a/[(1-ν2)Ec],其中Y是Youg’s模量,ν是Poisson比,Ec是矫顽场,α是裂纹长度;当电场垂直或平行于裂纹面时,ψ分别为2.3×10-4或1.3×10-4,而和电场正、负号以及极化状态无关。

The apparent fracture toughness of the lead zireonate titanate （PZT- 5 H） ceramic samples unpoled and poled along the length and thickness with applied electric field was investigated by the notched tensile method. The results show that the apparent fracture toughness of the sample decreases linearly with the increasing applied electric field in all states. The fracture criterion under combined electric and mechanical loading is K I （σ） ＋ K I （E）=KIc, where K I c is fracture toughness, K I （σ） and KI （E） are the stress intensity factors induced by the stress a and the field E, respectively. KI （E） =φbYE√a/（1 - v^2 ）Ec ], where Y is the Young＇s modulus, v is the Poisson ratio, Ec is the coercive field, a is the crack length and φ≈2.3×10^-4 for the field normal to the crack plane and φ≈1.3×10^-4 for the field parallel to the crack plane, respectively, which is independent of the poling state and the sign of the applied field.