Porous Li-Na-K niobate bone-substitute ceramics: Microstructure and piezoelectric properties

Abstract

Disc specimens of a porous ceramic, lithium sodium potassium niobate (Li0.06Na0.5K0.44)NbO3, were prepared using ammonium oxalate monohydrate or poly(methyl methacrylate) as pore-forming agent, and made piezoelectric using a modified polarizing method to preserve biocompatibility. Scanning electron microscopy showed a bicontinuous 3-3 structure of interconnected pores 150-250 μm in size. The piezoelectric constant (d33) and electromechanical coupling coefficient (Kp) are discussed as a function of porosity and pore shape: d33 fitted the theoretical expectation for shape factor Ks = 1, while Kp was approximately constant (~ 0.23) for porosity of 15-45 vol.%. 50 vol.% AOM gave the highest porosity (~ 45%) without decline of the value of Kp whilst maintaining mechanical integrity. Such materials show promise for use as a piezoelectric composite bone substitute. © 2008 Elsevier B.V. All rights reserved.