Ph. Papet

P–T phase diagram of PbZr0.52Ti0.48O3 (PZT)

Abstract The important piezoelectric material, lead zirconate titanate perovskite PbZr0.52Ti0.48O3 (PZT) was investigated as a function of pressure and temperature by Raman spectroscopy. At ambient pressure, the transition between the low-temperature and high-temperature ferroelectric monoclinic phases occurs near 210 K and is followed by transformation to the tetragonal phase at close to 305 K. The critical pressure for the transition to the disordered polar cubic phase increases with decreasing temperature from 5 GPa at 298 K to 9 GPa at 44 K. The ferroelectric monoclinic phases thus have an extended stability range at low temperatures and high pressure. A strong Raman spectrum is obtained for the cubic phase at high pressure over the temperature range between 44 and 298 K indicating the presence of polar nanodomains. A P–T phase diagram of this material is proposed based on the present results.

Structural Contribution to the Ferroelectric Fatigue in Lead Zirconate Titanate (PZT) Ceramics

Many ferroelectric devices are based on doped lead zirconate titanate (PZT) ceramics with compositions near the morphotropic phase boundary (MPB), at which the relevant materials properties approach their maximum. Based on a synchrotron x-ray diffraction study of MPB PZT, bulk fatigue is unambiguously found to arise from a less effective field induced tetragonal-to-monoclinic transformation, at which the degradation of the polarization flipping is detected by a less intense and more diffuse anomaly in the atomic displacement parameter of lead. The time dependence of the ferroelectric response on a structural level down to 250 μs confirms this interpretation in the time scale of the piezolectric strain response.

Li2B4O7 thin films prepared by the pyrosol process

Thin films of lithium tetraborate (Li2B4O7) were obtained by the pyrosol process based on the pyrolysis on a heated substrate of an aerosol produced by the ultrasonic spraying of a solution. The films exhibited some preferential crystalline orientations. The effect of various parameters such as the concentration of precursors in methyl alcohol, and the nature and temperature of the substrate were studied to control the morphology and the preferential orientation of the thin film.