Tape cast porosity-graded piezoelectric ceramics

In this work a functionally graded porous Nb-doped PZT material (PZTN) was produced by tape casting. Each step of the production process (slurry formulation, lamination and thermal treatments) was thoroughly investigated. Tapes with different carbon black (CB) amounts were produced. The conditions necessary to laminate 6 layers of different CB concentration were optimized by tailoring the binder to plasticizer volume ratio of each single green layer. Cracks and delaminations were eliminated by gradually increasing CB content and adjusting the binder burn-out procedure. The optimization process led to a well developed, crack-free porosity-graded multilayer, less than 400 μm thick and with porosity along the thickness ranging from 10 to 30 vol.%. The application of a load during the heating treatments was absolutely required to obtain warpage-free planar multilayer specimens.