Temperature dependent fracture toughness of KNN-based lead-free piezoelectric ceramics

Li Y, Liu Y, Öchsner PE, Isaia D, Zhang Y, Wang K, Webber KG, Li JF, Rödel J (2019)

Publication Type: Journal article

Publication year: 2019

Journal

Acta Materialia Elsevier

Book Volume: 174

Pages Range: 369-378

DOI: 10.1016/j.actamat.2019.05.060

Abstract

The fracture toughness of unpoled and electrically poled lead-free KNN-based piezoelectric ceramics with the composition of 0.92KNN-0.02Bi0.5Li0.5TiO3-0.06BaZrO3 was investigated. Results reveal that at room temperature, the intrinsic fracture toughness (KI0) of the unpoled samples, evaluated by the near-tip crack opening displacement (COD) technique, is the lowest with a value of 0.70 MPa⋅m^0.5; the long (through-thickness) crack fracture toughness (KIvnb), obtained by the single edge V-notch beam (SEVNB) technique, is the highest, with a value of 0.95 MPa⋅m^0.5; intermediate short surface crack fracture toughness (KIsc) of 0.86 MPa⋅m^0.5 was determined by the surface crack in flexure (SCF) technique. These results were rationalized by the toughening behavior of the material combined with the crack geometry-dependent stress intensity evolution during crack propagation. With increasing temperature, KIvnb and KIsc decrease, and become nearly identical at 350 °C, suggesting an absence of toughening. For electrically poled samples, their room temperature fracture toughness was characterized by both SCF and SEVNB techniques, with values of 0.88 MPa⋅m^0.5 and 0.99 MPa⋅m^0.5, respectively, slightly larger than the values measured for unpoled samples. Nonlinear electric field-strain and stress-strain analysis of the material was also employed during electric field loading, mechanical compression and four-point bending in order to quantify crack tip shielding by domain switching and the actual stress at the point of instable crack propagation.

Authors with CRIS profile

Paul-Erich Öchsner Lehrstuhl für Glas und Keramik Kyle Grant Webber Professur für Werkstoffwissenschaften (Funktionskeramik)

Involved external institutions

Technische Universität Darmstadt

Germany (DE) Tsinghua University

China (CN)

How to cite

APA:

Li, Y., Liu, Y., Öchsner, P.-E., Isaia, D., Zhang, Y., Wang, K.,... Rödel, J. (2019). Temperature dependent fracture toughness of KNN-based lead-free piezoelectric ceramics. Acta Materialia, 174, 369-378. https://dx.doi.org/10.1016/j.actamat.2019.05.060

MLA:

Li, Yingwei, et al. "Temperature dependent fracture toughness of KNN-based lead-free piezoelectric ceramics." Acta Materialia 174 (2019): 369-378.

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