V. Dimza

Radiation effects on lead-containing perovskite ceramics

Abstract Optical spectra and dielectric parameters are used to study PLZT X/65/35 (X=4.5−11 at.% La) and PSN ceramics subject to gamma- electron-, and neutron irradiation. In neutron-irradiated ceramics stable defects, maintained at annealing up to 700 °C are manifested by a gradual shift of extinction edge near the fundamental absorption to longer wavelengths and by reduced polarization values. The thermal dependence of the extinction edge in reference samples of PLZT and PSN has been determined to be ca. 0.10 nm/deg (0.9 meV/deg) and 0.125 nm/deg, respectively in the range 20-500°C. In PLZT 6.5-8/65/35 ceramics a defect enforced phase transformation from the initial rhombohedral structure to “quasicubic” with essential broadening of the phase transition takes place.

Studies of Raman scattering spectra (RSS) of PLZT and PMN ceramics doped with 3d elements

Abstract This paper deals with Raman scattering room temperature spectra in a) PLZT X/65/35 (X = 0; 2; 8; 13 at.%); b) PLZT 8/65/35 with a different degree of deficiency of O2 and Pb; c) PLZT 8/65/35 and PMN ceramics doped with 3d elements (Cr, Mn, Fe, Co, Ni, Cu).

Dielectric memory effects of (Mn, Fe, Co, Cu, Eu) doped PLZT ceramics

Abstract Dielectric memory effects—effect of thermal memory (ETM) and effect of electric field memory (EFM) have been studied in (Mn, Fe, Co, Cu, Eu) doped PLZT ceramics. The obtained results have been discussed on the assumption that the ETM and EFM depends on relaxation of domain and interphase (polar and nonpolar) boundaries influenced by changes of defects conditions at doping.

FE3+EPR investigation of PLZT 1/65/35 and 8/65/35

Abstract X-band EPR spectra of PLZT 1/65/35 and PLZT 8/65/35 doped with 1% FE3+ were recorded at temperature range −175°C to 200°C. Three types of paramagnetic centers were found. Two of them are in strong axial and rhombic crystal field due to neighboring oxygen and lead vacancies. The other center has symmetry determined by polarization and oxygen octahedra tilt. EPR spectra of PLZT 8/65/35 are in agreement with its glassy behavior.

The Effects of 3d Admixtures on Properties of Relaxor PLZT8/65/35 Ceramics

A study of the effects of the 3d dopants Mn, Fe, Co, Ni, and Cu on relaxor behavior and other properties of the ferroelectric PLZT8/65/35(La8) ceramic compound by X-ray diffraction, electron microscopy and other techniques is reported. The complex dielectric permittivity ϵ* = ϵ′-iϵ′′ is measured in the 20–400°C range of temperature at frequencies within the range of 102 – 106 Hz. Essential changes caused by the admixtures in the behavior of dielectric permittivity with frequency and temperature are observed along with changes in the XRD SEM patterns are observed. The mechanisms of the phenomena are discussed.

Electron-microscopy studies of pure and doped electrooptic PLZT ceramics

Abstract Data on chemical composition and spatial fluctuations thereof as well as fracture mode behaviour of pure and doped PLZT ceramics have been obtained.

Aging and Memory Effects in PLZT 8/65/35 Ceramics Modified with 3d Transition-Metal Ions

The temperature and frequency dependencies of the dielectric susceptibility in relaxor electro-optical PLZT 8/65/35 modified with 3d transition-metal ions (Mn, Fe, Co, Ni) measured to study the aging and memory effects are reported. The studies of aging at room temperature show that 3d admixtures (Me) in PLZT 8/65/35 ceramics at small to medium concentration range (Me < 1.0 wt.%) change the depth of dispersion, the aging amplitude and the temperature range of the memory effect. At admixture concentrations Me →1.0 wt% the aging and memory effect are significantly reduced (or eliminated). The obtained results suggest that aging effects are determined by two substantial acceptor effects of the introduced ions: 1) formation of Me2+- VO (oxygen vacancy) dipoles and 2) Jahn-Teller effect.

Using the methods of radiospectroscopy (EPR, NMR) to study the nature of the defect structure of solid solutions based on lead zirconate titanate (PZT)

The nature of intrinsic and impurity point defects in lead zirconate titanate (PZT) ceramics has been explored. Using electron paramagnetic resonance (EPR), nuclear magnetic resonance (NMR), and X-ray photoelectron spectroscopy (XPS) methods, several impurity sites have been identified in the materials, including the Fe3+-oxygen vacancy (VO) complex and Pb ions. Both of these centers are incorporated into the PZT lattice. The Fe3+-V paramagnetic complex serves as a sensitive probe of the local crystal field in the ceramic; the symmetry of this defect roughly correlates with PZT phase diagram as the composition is varied from PbTiO3 to PbZrO3. NMR spectra 207Pb in PbTiO3, PbZrO3, and PZT with iron content from 0 to 0.4 wt% showed that increasing the iron concentration leads to a distortion of the crystal structure and to improvement of the electrophysical parameters of the piezoceramics. This is due to the formation of a phase which has a higher symmetry, but at high concentrations of iron (>0.4 wt%), it leads to sharp degradation of electrophysical parameters.

Structure and properties of PLZT 1/65/35 ceramics doped with Mn and Fe

Abstract The present paper deals with X-ray studies, dielectric measurements, linear expansion and Raman scattering in PLZT 1/65/35 ceramics doped with Mn and Fe. Admixture of Mn and Fe is found to increase the phase transition temperature and to appear in the tetragonal structure.