Browsing by Author "Venturini, E.L."

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Dielectric properties and phase transitions of [Pb(Zn1/3Nb2/3)O3]0.905(PbTiO3)0.095: Influence of pressure
(2001-04-18) Samara, G.A.; Venturini, E.L.; Schmidt, V. Hugo
Studies of the influences of temperature, hydrostatic pressure, dc biasing field, and frequency on the dielectric constant (ɛ′) and loss (tanδ) of single crystal [Pb(Zn1/3Nb2/3)O3]0.905(PbTiO3)0.095, or PZN-9.5 PT for short, have provided a detailed view of the ferroelectric (FE) response and phase transitions of this technologically important material. While at 1 bar, the crystal exhibits on cooling a cubic-to-tetragonal FE transition followed by a second transition to a rhombohedral phase, pressure induces a FE-to-relaxor crossover, the relaxor phase becoming the ground state at pressures ⩾5 kbar. Analogy with earlier results suggests that this crossover is a common feature of compositionally disordered soft mode ferroelectrics and can be understood in terms of a decrease in the correlation length among polar domains with increasing pressure. Application of a dc biasing electric field at 1 bar strengthens FE correlations, and can at high pressure restabilize the FE response. The temperature-pressure and temperature-electric field phase diagrams were established. In the absence of dc bias the tetragonal phase vanishes at high pressure, the crystal exhibiting classic relaxor behavior. The dynamics of dipolar motion and the strong deviation from Curie-Weiss behavior of the susceptibility in the high-temperature cubic phase are discussed.
Pressure-induced crossover from long‑to‑short‑range order in [Pb(Zn1/3Nb2/3)O3]0.905 (PbTiO3)0.095 single crystal,
(2000) Samara, G.A.; Venturini, E.L.; Schmidt, V. Hugo
A pressure-induced crossover from normal ferroelectric–to–relaxor behavior has been observed in single crystal [Pb(Zn1/3Nb2/3)O3]0.905(PbTiO3)0.095, or PZN-9.5% PT. Analogy with similar observations for other perovskites indicates that this crossover is a general feature of compositionally disordered soft mode ferroelectrics. The pressure-temperature phase diagram has been also determined.