Using the Czochralski method we have grown LiNbO3 crystals with periodic laminar ferroelectric domains whose half-period nearly corresponds to the coherence length. Quasi-phase-matching for the nonlinear optical coefficient d33 has been approximately realized and enhancement of second-harmonic generation relative to conventionally phase-matched crystals of the same length has been observed.

Pure Bi4Ti3O12 ceramics were prepared using the conventional solid-state reaction method and their dielectric properties were investigated. A dielectric loss peak with the relaxation-type characteristic was observed at about 370K at 100Hz frequency. This peak was confirmed to be associated with the migration of oxygen vacancies inside ceramics. The Cole–Cole fitting to this peak reveals a strong correlation among oxygen vacancies and this strong correlation is considered to commonly exist among oxygen vacancies in ferroelectrics. Therefore, the migration of oxygen vacancies in ferroelectric materials would demonstrate a collective behavior instead of an individual one due to this strong correlation. Furthermore, this correlation is in proportion to the concentration and in inverse proportion to the activation energy of oxygen vacancies. These results could be helpful to the understanding of the fatigue mechanisms in ferroelectric materials.

The coexistence of MA (space group Cm) and MC (space group Pm) phases in as-grown Pb(Mg1∕3Nb2∕3)0.68Ti0.32O3 (PMNT32) single crystals is observed at room temperature under polarization microscopy. Laminar MA and MC domains normal to ⟨110⟩cub direction appear alternately in PMNT32 single crystals. In the heating run, the MA domains show a phase transition sequence of MA-MC-cubic, while the MC domains show only a phase transition of MC to cubic. In the cooling run, the phase transition sequence of cubic-MC-MA can be observed in the whole sample. It is suggested that the internal stress in the as-grown PMNT crystals is the main reason for the coexistence of the MA and MC phases.

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