Poling treatment and piezoelectric properties of potassium niobate ferroelectric single crystals

Citation
S. Wada et al., Poling treatment and piezoelectric properties of potassium niobate ferroelectric single crystals, JPN J A P 1, 40(9B), 2001, pp. 5690-5697
Citations number
24
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Apllied Physucs/Condensed Matter/Materiales Science
Volume
40
Issue
9B
Year of publication
2001
Pages
5690 - 5697
Database
ISI
SICI code
0021-4922(200109)40:9B<5690:PTAPPO>2.0.ZU;2-8
Abstract
Piezoelectric properties of potassium niobate (KNbO3) single crystals were investigated as a function of crystallographic orientations, i.e., [110](c) of polar direction and [001](c) of nonpolar direction. Prior to the piezoe lectric measurements, the optimum conditions for a conventional poling meth od were investigated, and it was found that the optimum conditions for a co nventional poling method were as follows, i.e., (a) high temperature above 100 degreesC, (b) long soaking time over 1 h, (c) slow heating and cooling rates below 1 degreesC/min, and d) lower poling current below I muA. Howeve r, fully poled KNbO3 crystals were not obtained using the conventional poli ng method. Thus, to achieve fully poled KNbO3 single crystals, a new 2-step , poling method was proposed. This method is composed of 2 poling stages, i .e., the I st step for non- 180 degrees domain switchings at higher tempera tures under a low DC bias field, and the 2nd step for 180 degrees domain sw itchings at lower temperatures under a high DC bias field. Using the 2-step poling method, KNbO3 crystals were successfully poled, and then, their pie zoelectric properties of k(31) modes were measured using a resonance method . The [110](c) poled KNbO3 crystals exhibited electromechanical coupling fa ctor k(31) of 29.9% and piezoelectric constant d(31) of 18.4 pC/N while the [001](c) poled KNbO3 crystals exhibited k(31) of 31.2% and d(31) of 51.7 p C/N. The piezoelectric constant d(31) along nonpolar [001](c) direction was 2.8 times higher than that along polar [110](c) direction.