Ultrahigh Performance Piezoelectric Energy Harvester Using Lead-Free Piezoceramics with Large Electromechanical Coupling Factor

Abstract

The output power of piezoelectric energy harvester (PEH) at the resonance frequency is dependent on the electromechanical coupling factor ( k p ) of the piezoceramic, which is proportional to d 33 / ε T 33 1 / 2 , where d 33 and ε T 33 are the piezoelectric change and dielectric constants, respectively. Therefore, the piezoceramic for the PEH should have a large d 33 and a small ε T 33 . [001]-texturing can be used for developing piezoceramics for PEH because it generally increases d 33 without increasing ε T 33 . The 0.96(K0.5Na0.5)(N1-zSz)O3-0.03(Bi0.5Ag0.5)ZrO3-0.01SrZrO3 [KN(N1-zSz)-BAZ-SZ] piezoceramics were textured along the [001] orientation, and the piezoceramic ( z = 0.01 ) showed a large k p of 0.77, which is the largest k p for KNN-related piezoceramics reported in the literature. The cantilever-type PEH manufactured using the KN(N0.99S0.01)-BAZ-SZ piezoceramic exhibited a large output power density of 7.86 mW/cm3 at resonance frequency because of its large k p . To date, this is the largest power density for PEHs manufactured utilizing lead-free piezoceramics. Hence, the [001]-textured KN(N0.99S0.01)-BAZ-SZ piezoceramic is an excellent candidate for PEH, and [001]-texturing is a very efficient method for developing piezoceramics for PEH.

Optimized physical properties of [001]-textured (Na, K)NbO3-based lead-free piezoceramics for high power piezoelectric energy harvesters

“…S6(f), ESI†) with a P S direction along the [001] direction. 29,39,60 Previous studies reported identical results. 29,39,60…”

“…It has been reported that the P out of type-I harvesters at f R is affected by the k p 2 of the composition. 10,39 Fig. 10(d) shows the P out of the harvesters and the k p 2 value of the textured NK(N 1− x S x )–CZ–BAZ 0.0 ≤ x ≤ 0.1 compositions, which shows that the change in the P out value was identical to that of the k p 2 value.…”

“…According to previous studies on NKN-based piezoceramics with a R–O–T structure, the stain improvement is significant when the proportion of R–O structure is greater than 80%, whereas the strain improvement is comparatively small when the proportion of R–O structure is less than 80%. 29,39,60 The strain of the NK(N 1− x S x )–CZ–BAZ piezoceramics increased after [001]-texturing. Although the strain enhancement was significant for the piezoceramics with x ≤ 0.05, it was relatively small when x exceeded 0.05 (Fig.…”

“…9(b)). 9,10,29,39 Additionally, Fig. 9(c) shows the voltage measurement system with the equivalent circuit of the harvester.…”

“…15 × 15 × 0.4 mm [001]-textured piezoceramic plates were attached to 15 × 60 × 0.4 mm steel substrates (SUS304) using DP-420 epoxy. The cantilever beam of piezoelectric energy harvesters are typically fabricated from a steel substrate; 37–45 thus, steel was utilized as the substrate of the piezoelectric energy harvester in this study. The steel substrate had dimensions of 15 × 60 × 0.4 mm because the resonance frequencies of a harvester with these dimensions are similar to those of many other ambient vibration sources.…”