Charge Trapping Centers in Ferroelectric Ceramics

1992 ◽  
Vol 284 ◽  
Author(s):  
C. H. Seager ◽  
W. L. Warren ◽  
B. A. Tuttle ◽  
R. D. Nasby ◽  
D. Dimos
Keyword(s):  
Uv Light ◽  
Charge Trapping ◽  
Ferroelectric Ceramics ◽  
Electrical Measurements ◽  
Lead Lanthanum Zirconate Titanate ◽  
Paramagnetic Resonance ◽  
Lanthanum Zirconate ◽  
Polarization Electric Field ◽  
Crystal Field Parameters ◽  
Electron Paramagnetic

ABSTRACTElectron paramagnetic resonance (EPR), photo-thermal deflection spectroscopy (PDS), and electrical measurements have been used to characterize as-received and UV-lluminated lead lanthanum zirconate titanate (PLZT) and PZT ceramics. Following optical illumination we observe the activation of positively charged Pb+3 and negatively charged Ti+3 ions, as well as an increased broad absorption peak around 2.6 eV. The spatial distribution of the induced absorption correlates well with the location of the absorbed UV, suggesting that photo-produced carrier pairs are trapped at Ti+4 and Pb+2 producing the observed paramagnetism. The Ti+3 EPR spectra were successfully fit using the crystal field parameters derived from the PDS spectra. Preliminary results suggest that these charged paramagnetic ions can influence the electrical properties of PZT thin films. We investigated the effects of UV light and dc bias sequences by polarization-electric field (PE) measurements and find that the coercive fields are dependent on the sign of the applied bias during UV exposure. It is reasonable to expect that Pb+3 and/or Ti+3 ions act as the charge trapping sites which cause the threshold voltage shifts in the PE loop.

Optical Imaging and Information Storage in Ion Implanted Ferroelectric Ceramics

1981 ◽  
Vol 7 ◽  
Author(s):  
P. S. Peercy ◽  
C. E. Land
Keyword(s):  
Uv Light ◽  
Visible Spectrum ◽  
Dark Conductivity ◽  
Information Storage ◽  
Ferroelectric Ceramics ◽  
Lead Lanthanum Zirconate Titanate ◽  
Lanthanum Zirconate ◽  
Photographic Images ◽  
Intrinsic Photosensitivity ◽  
Ion Implanted

ABSTRACTPhotographic images can be stored in ferroelectric-phase lead lanthanum zirconate titanate (PLZT) ceramics using a novel photoferroelectric effect. These images are nonvolatile but erasable and can be switched from positive to negative by application of an electric field. We have found that the photosensitivity of ferroelectric PLZT is dramatically improved by ion implantation into the surface exposed to image light. For example, the intrinsic photosensitivity to near-UV light is increased by as much as four orders of magnitude by coimplantation with Ar and Ne. The increased photosensitivity results from implantation-induced decreases in dark conductivity and dielectric constant in the implanted layer. Furthermore, the increased photoferroelectric sensitivity has recently been extended from the near-UV to the visible spectrum by implants of Al and Cr. Ion-implanted PLZT is the most sensitive, nonvolatile, selectively-erasable image storage medium currently known.

Studies of local structures for Cu2+ centers in M2Zn(SO4)2·6H2O (M = NH4 and Rb) crystals

2021 ◽  
Vol 76 (4) ◽  
pp. 299-304
Author(s):  
Fu Chen ◽  
Jian-Rong Yang ◽  
Zi-Fa Zhou
Keyword(s):  
Crystal Field ◽  
Elongation Ratio ◽  
Paramagnetic Resonance ◽  
Local Structures ◽  
Epr Parameters ◽  
Structure Constants ◽  
Crystal Field Parameters ◽  
Electron Paramagnetic ◽  
Theoretical Results ◽  
Good Agreement

Abstract The electron paramagnetic resonance (EPR) parameters (g factor g i , and hyperfine structure constants A i , with i = x, y, z) and local structures for Cu2+ centers in M2Zn(SO4)2·6H2O (M = NH4 and Rb) are theoretically investigated using the high order perturbation formulas of these EPR parameters for a 3d 9 ion under orthorhombically elongated octahedra. In the calculations, contribution to these EPR parameters due to the admixture of d-orbitals in the ground state wave function of the Cu2+ ion are taken into account based on the cluster approach, and the required crystal-field parameters are estimated from the superposition model which enables correlation of the crystal-field parameters and hence the studied EPR parameters with the local structures of the Cu2+ centers. Based on the calculations, the Cu–H2O bonds are found to suffer the axial elongation ratio δ of about 3 and 2.9% along the z-axis, meanwhile, the planar bond lengths may experience variation ratio τ (≈3.8 and 1%) along x- and y-axis for Cu2+ center in (NH4)2Zn(SO4)2·6H2O and Rb2Zn(SO4)2·6H2O, respectively. The theoretical results show good agreement with the observed values.

Investigations of the EPR g Factors for Er3+ in CaMoO4

2004 ◽  
Vol 59 (6) ◽  
pp. 341-345 ◽  
Author(s):  
Shao-Yi Wu ◽  
Hui-Ning Dong
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Crystal Field ◽  
Structural Data ◽  
Order Perturbation ◽  
Tetragonal Symmetry ◽  
Superposition Model ◽  
Paramagnetic Resonance ◽  
Crystal Field Parameters ◽  
Electron Paramagnetic ◽  
G Factors

The electron paramagnetic resonance (EPR) g factors g‖ and g⊥ for Er3+ in CaMoO4 are theoretically investigated by using the perturbation formulas of the g factors for a 4f11 ion in tetragonal symmetry. In these formulas, the contributions to the g factors arising from the second-order perturbation terms and the admixture of various states are considered. The crystal-field parameters for the tetragonally distorted tetrahedra are determined by using the superposition model and the structural data of the impurity Er3+ on the host Ca2+ site in CaMoO4. The calculated g factors agree with the observed values. The validity of the results is discussed.

Sol-Gel Transparent PLZT Ferroelectric Ceramics

2006 ◽  
Vol 45 ◽  
pp. 2489-2494 ◽  
Author(s):  
M. Płońska ◽  
Wojciech A. Pisarski ◽  
Zbigniew Pędzich ◽  
Zygmunt Surowiak
Keyword(s):  
Infrared Spectroscopy ◽  
Mercury Porosimetry ◽  
Sol Gel ◽  
Ferroelectric Ceramics ◽  
Ceramic Powders ◽  
Lead Lanthanum Zirconate Titanate ◽  
Lanthanum Zirconate ◽  
Pressing Method ◽  
Fine Grained ◽  
To Receive

Lead lanthanum zirconate titanate (known as PLZT) ceramic powders have been prepared by the modified sol – gel method, and underwent consolidation by the hot uniaxial pressing method. Application of such technique of preparation permitted to receive fine-grained transparent PLZT x/65/35 ceramics, with x = 8 -10 La at.%. The present publication gives a detailed account of the relationships between technology and physical properties of obtained materials. To analyze all ceramics SEM, EDS and mercury porosimetry were performed, and dielectric properties were studied too. Quite wide light transparency from the visible to nearinfrared range for PLZT ceramics was detected using optical absorption and infrared spectroscopy.

scholarly journals On the incorporation of nickel into hexagonal barium titanate: magnetic properties and electron paramagnetic resonance (EPR)

2020 ◽  
Vol 56 (8) ◽  
pp. 4967-4978
Author(s):  
R. Böttcher ◽  
H. T. Langhammer ◽  
T. Walther ◽  
S. Kücker ◽  
S. G. Ebbinghaus
Keyword(s):  
Magnetic Properties ◽  
Barium Titanate ◽  
Paramagnetic Susceptibility ◽  
Oxygen Octahedra ◽  
Temperature Dependent ◽  
Paramagnetic Resonance ◽  
Forbidden Transition ◽  
The Face ◽  
Crystal Field Parameters ◽  
Electron Paramagnetic

AbstractSystematic measurements of the magnetic moment of hexagonal 6H-BaTiO3 + 0.04 BaO + x NiO (0.005 ≤ x ≤ 0.02) ceramics were performed to study the influence of Ni ions on the magnetic properties. By temperature-dependent measurements of the paramagnetic susceptibility at 90 kOe, the Ni2+ ion was identified as the majority defect in air-sintered Ni-doped hexagonal barium titanate. Q-band EPR investigations of a 2.0 mol% Ni-doped single crystal revealed three different Ni centers located at Ti sites: first, Ni3+ ions at Ti sites in intact oxygen octahedra, second, Ni3+ associated with an oxygen vacancy and third, the presence of Ni2+ centers leading to a forbidden transition. The Ni3+—VO associate characterized by a vacancy in the face-sharing oxygen plane of the oxygen octahedra can be ruled out. The crystal field parameters of the Ni2+ defect were estimated by a combined fitting of the paramagnetic susceptibility and the EPR fine structure parameter D to $$B_{0}^{4}$$ B 0 4 ≈ −17,300 cm−1, $$\left| {B_{0}^{2} } \right|$$ B 0 2 ≈ 2500 cm−1 and $$B_{3}^{4}$$ B 3 4 ≈ 19,000 cm−1.

Theoretical Investigations of the Electron Paramagnetic Resonance g Factors for the Trivalent Cerium Ion in LiYF4 Crystal

2003 ◽  
Vol 58 (9-10) ◽  
pp. 507-510
Author(s):  
Hui-Ning Dong ◽  
Shao-Yi Wu
Keyword(s):  
Tetragonal Symmetry ◽  
Superposition Model ◽  
Paramagnetic Resonance ◽  
Cerium Ion ◽  
Theoretical Investigations ◽  
Epr Parameters ◽  
Crystal Field Parameters ◽  
Electron Paramagnetic ◽  
Perturbation Equations ◽  
G Factors

The perturbation equations of the EPR parameters g‖ and g⊥ for the lowest Kramers doublet of a 4f1 ion in tetragonal symmetry are established. In these equations, the contributions of the covalency effects, the admixture between J = 7/2 and J = 5/2 states and the second-order perturbation (which is not considered previously) are included. The crystal field parameters for the studied Ce3+ center are calculated from the superposition model. Based on the above perturbation equations and related parameters, the EPR g factors for the Ce3+ center in LiYF4 crystals are reasonably explained. The results are discussed.

Effect of Nd3+ concentration quenching in highly doped lead lanthanum zirconate titanate transparent ferroelectric ceramics

2007 ◽  
Vol 101 (5) ◽  
pp. 053111 ◽  
Author(s):  
A. S. S. de Camargo ◽  
C. Jacinto ◽  
L. A. O. Nunes ◽  
T. Catunda ◽  
D. Garcia ◽  
...  
Keyword(s):  
Concentration Quenching ◽  
Ferroelectric Ceramics ◽  
Lead Lanthanum Zirconate Titanate ◽  
Lanthanum Zirconate ◽  
Zirconate Titanate
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