Lead zirconate titanate (PZT) is an inorganic, ceramic, piezoelectric, crystal used in ultrasound transducers. The chemical formula of PZT is Pb[Zr(x), Ti(1-x)]O3, e.g. PbZr(0..52)Ti(0.48) O3. Each individual PZT lattice cell has piezoelectric potential due to the dipole created by the asymmetry of the position of its atoms. Newly-formed PZT crystals are a mixture of rhombohedral and tetragonal lattice cells due to the random orientation of their dipoles. Zr atoms tend to form rhombohedral cells and Ti atoms tend to form tetragonal cells. Before PZT can be used in ultrasound transducers it must be poled, in a process using heat and an electric field, to align the atom dipoles.
Image 1 (left image): a single PZT cell with a tetragonal shape and dipole
Image 2: when first formed, PZT crystals have random dipole positions that cancel out the overall piezoelectric effect. Atoms: Pb - grey, O - blue, Ti - green, Zr - cream
Image 3: at the Curie temperature of PZT and above it, the lattice and atoms morph into symmetrically cubic cells with central Zr and Ti atoms and no piezoelectric effect
Image 4: the temperature is dropped below the Curie point and an electric field morphs the lattice cells into a tetragonal pattern with a piezoelectric potential
Case Discussion
Author: David McGrath
Illustrations and Animation by: David McGrath
Original video file: https://www.youtube.com/watch?v=Gp-P8D1i4Ps
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