Influence of Cell Size on Mechanical and Piezoelectric Properties of PZT and LNKN Ceramic Foams

Abstract

Piezoceramic foams made of lead zirconate titanate (PZT) and lithium sodium potassium niobate containing an open porosity >75 vol% are manufactured with varying cell size from 1369 to 265 mm and accordingly, strut size from 346 to 46 mm by replica method. Pore size distribution and strut thickness are determined by X-ray micro tomography investigations of PZT foams with 10, 30, 45, and 80 pores per inch (ppi). Fracture strengths s b between 0.29 and 1.52 MPa (PZT) and 0.04 and 0.07 MPa (LNKN-6) are determined by compression test and compared to Gibson and Ashby's model of open-and closed-cell foams and in dependence of the cell size. The longitudinal and transversal coupling coefficients d 33 and d 31 decrease in a range of 38 to 178 pCN À1 or À13 to À100 pCN À1 compare to dense reference material. In dependence of the cell size, the values of the coupling coefficients change about 79-93%. The relative permittivity decreases 93% by decreasing the cell size of the PZT and LNKN-6 foams.

Temperature‐ and Stress‐Dependent Electromechanical Response of Porous Pb(Zr,Ti)O3

“…[7] For piezoelectric materials, such as lead-free Li-doped potassium sodium niobate or Pb(Zr,Ti)O 3 (PZT), the effects of pore morphology, pore size, amount of porosity, and degree of isotropy on the properties, e.g., enhanced d h and reduced relative permittivity compared with dense piezoelectric ceramics, were reported. [8][9][10][11][12][13][14] Despite the improvement in electromechanical response, porosity decreases the mechanical strength, effectively limiting pore content. [15] This is particularly critical, as many applications apply elevated electrical, thermal, and mechanical fields to the electroactive materials during operation.…”

Ultrahigh‐strength alumina ceramic foams via gelation of foamed boehmite sol

“…The average grain size of about 150 nm at 1200°C is smaller than that of most existing alumina foams obtained from commercial alumina powder. (b) Small average pore size and narrow pore size distribution . Compared to plenty of other methods, the current approach can acquire smaller pore size of 5‐70 μm and narrower pore size distribution.…”

“…(b) Small average pore size and narrow pore size distribution. 10,11 Compared to plenty of other methods, the current approach can acquire smaller pore size of 5-70 μm and narrower pore size distribution. (c) Hierarchical pore structure.…”

“…Recently, hierarchical structuring of these materials has attracted increasing scientific interest because hierarchically porous architectures outperform others with respect to mechanical strength . Furthermore, excellent strength can be also acquired from smaller grain size and pore size . So far, a variety of preparation methods, such as replica, sacrificial template, and direct foaming have been developed for the fabrication of ceramic foams .…”

“…7,8 Furthermore, excellent strength can be also acquired from smaller grain size 9 and pore size. 10,11 So far, a variety of preparation methods, such as replica, sacrificial template, and direct foaming have been developed for the fabrication of ceramic foams. 1,[12][13][14][15][16][17] In the porosity regimes higher than 60%, direct foaming is a facile and universal strategy to tune pore structure and porosity.…”