Surface Modification by Stearic Acid on Property of PLZT Piezoelectric Ceramics Prepared via Powder Injection Molding

doi:10.15541/jim20180323

Abstract

Abstract:

A powder injection molding feedstock of lead zirconate titanate (PLZT) was successfully prepared using stearic acid as powder modifier and polyethylene glycol/polyvinyl butyral/polyoxymethylene (PEG/PVB/POM) as binder system. Then, PLZT piezoelectric ceramics were prepared by degreasing and post-sintering processes. The effects of stearic acid (SA) dosage on powder properties, feedstock viscosity, water degreasing rate and green body strength were studied. The microstructure and electrical properties of the sintered ceramics were compared and analyzed. The results showed that stearic acid was successfully coated onto the PLZT powder by wet modification. The modification of stearic acid broke the agglomeration between the powders, and when the amount of stearic acid was 2wt%, the feedstock had a lower shear viscosity and a higher green body bending strength. However, excessive modification caused the feed viscosity to increase and the bending strength of the green body to decrease. The modified powder was uniformly dispersed in the body, and the sintered ceramic had higher density with well grown grains. As compared to the unmodified sample, the piezoelectric constant d₃₃ of the PLZT modified with 2wt% SA increased from 638 pC/N to 682 pC/N.

Key words: stearic acid, powder modification, PLZT, injection molding, piezoelectric performance

CLC Number:

TF124

Dun WU, Shuai QIN, Chun-Lin LIU, Bi-Jun FANG, Zheng CAO, Jun-Feng CHENG. Surface Modification by Stearic Acid on Property of PLZT Piezoelectric Ceramics Prepared via Powder Injection Molding[J]. Journal of Inorganic Materials, 2019, 34(5): 535-540.

Figures/Tables 13

Fig. 1 Infrared spectra of stearic acid and powder before and after modification

Fig. 2 SEM images of PLZT powder before (a) and after (b) modification

Fig. 3 Rheological properties of feedstock with different contents of stearic acid

Fig. 4 Bending strength of green body and brown body

Fig. 5 Schematic diagram of the process of water degreasing

Fig. 6 Curves of degreasing rate with degreasing time

Fig. 7 Surface SEM images of the green body and brown body

Fig. 8 XRD patterns of modified and unmodified PLZT piezoelectric ceramics

Fig. 9 Surface SEM images of PLZT sintered at different temperatures

Table 1 Porosities and densities of ceramics sintered at different temperatures

Sample	1200 ℃		1240 ℃		1280 ℃
Sample	Porosity/%	Density/(g·cm^-3)	Porosity/%	Density/(g·cm^-3)	Porosity/%	Density/(g·cm^-3)
Unmodified	2.45	6.42	0.12	7.54	0.07	7.63
Modified	0.91	7.23	0.04	7.62	0.02	7.68

Fig. 10 Temperature dependence of dielectric constant (a) and dielectric loss (b) for PLZT piezoelectric ceramics at 100 kHz

Fig. 11 Hysteresis loops of PLZT piezoelectric ceramics at 13 kV/cm and 10 Hz

Fig. 12 Relationship between piezoelectric constant and polarization voltage of PLZT piezoelectric ceramics

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