Hollow lead zirconate titanate microspheres prepared by sol-gel/emulsion technique

Hollow spheres of lead zirconate titanate (PZT) (chemical formula: Pb(Zr0.52Ti0.48)O3) with about 50 μm outer diameter and 2 μm wall thickness were prepared by coating polyacrylamide latex microspheres in an emulsion with PZT gel and subsequently burning the polymer core. First, an emulsion of polyacrylamide microspheres, soaked with ammonia, was prepared with toluene. Then a PZT sol, prepared by dissolving Pb(NO3)2, Ti(OC3H7)4 and Zr(C4H9O)4 in an organic solvent, was poured into the polymer emulsion. Ammonia absorbed in the polymer spheres caused gelation on the surface of the spheres. The gel-coated spheres were calcined in air at 600–700 °C for 4 h to produce PZT perovskite phase. The discs made by sintering spheres at 850 °C for 4 h has 24% of the theoretical density and showed good piezoelectric properties. The present technique has been extended to prepare PZT spheres of outer diameter as large as 0.6 mm. PZT hollow spheres have potential applications in low-density transducer arrays.