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

Abstract

Disc specimens of a porous ceramic, lithium sodium potassium niobate (Li 0.06Na 0.5K 0.44)NbO 3, 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 ( d 33) and electromechanical coupling coefficient (Kp) are discussed as a function of porosity and pore shape: d 33 fitted the theoretical expectation for shape factor K s = 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.