Influence of carbon black on slurry compositions for tape cast porous piezoelectric ceramics

Functionally graded porous piezoceramics are of interest for ultrasonic applications as the gradual decrease of acoustical impedance improves the transfer of acoustic energy to water or biological tissues, assuring at the same time an high piezoelectric response. This ceramic architecture can be easily produced by tape casting as long as each step of the production process (slurry formulation, lamination and thermal treatments) is fully optimized. A thorough discussion on the process of slurry optimization is here reported. The Carbon Black (CB) was chosen as pore former agent and slurry formulations with CB concentration ranging between 3 and 43 vol% referred to the ceramic powder were optimized. Linear relationships between CB and solvent, binder and plasticizers amounts were found. The additional polymer (AP) required to optimize the slurry formulations was found to proportionally increase with CB amount. The abovementioned linear relationships were shown to allow an easy planning of the slurry composition to obtain defects-free green tapes for any CB concentration in the range considered.