Ferroelectric Phase Transition in Lead Germanate Crystals Doped with Off-Center Cu2+ Ions

• Published in: Ferroelectrics Vol. 330; no. 1; pp. 61 - 74
• Main Authors: Trubitsyn, M. P., Waplak, S., Kudzin, A. Yu
• Format: Journal Article
• Language: English
• Published: London Taylor & Francis Group 01.01.2006; Taylor and Francis
• Subjects: 61.72.Hh; 76.30.Fc; 77.22.G; 77.80.Bh; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Dielectric loss and relaxation; Dielectric properties of solids and liquids; dielectric relaxation; Dielectrics, piezoelectrics, and ferroelectrics and their properties; electron paramagnetic resonance; Electron paramagnetic resonance and relaxation; Exact sciences and technology; Ferroelectric phase transition; Ferroelectricity and antiferroelectricity; Magnetic resonances and relaxations in condensed matter, mössbauer effect; Phase transitions and curie point; Physics; structural defect; Dielectric dispersion; Crystal defects; Doping; Dynamic properties; Copper additions; 76.30.Fc; Ferroelectric phase transition; structural defect; electron paramagnetic resonance; dielectric relaxation; 77.80.Bh; 61.72.Hh; Dielectric relaxation; Phenomenological model; Ferroelectric transitions; 77.22.G; Impurity site; Lead Germanates; Electron paramagnetic resonance; Activation energy
• ISSN: 0015-0193; 1563-5112
• DOI: 10.1080/00150190600605544

EPR and dielectric properties of lead germanate Pb 5 Ge 3 O 11 (PGO) crystals doped with Cu 2+ are reported. EPR spectra testify that Cu 2+ substitute for Pb 2+ in the sites of trigonal point symmetry and equi-probably occupy one of three off-center positions shifted from lattice point in the plane perpendicular to polar axis c. Motional averaging of low symmetry EPR spectra just as low frequency dielectric dispersion indicate thermally activated hopping of Cu 2+ ions between off-center positions. Own frequency (τ 0 ) −1 ∼10 12 Hz and activation energy W = 0.24 eV of Cu 2+ local dynamics have been determined from EPR and dielectric measurements. Properties of PGO:Cu 2+ near ferroelectric phase transition are discussed on the basis of semi-phenomenological approach. It has been shown that PGO properties are influenced through static distortions accompanying Cu 2+ off-center location in the structure. Local dynamics of Cu 2+ ions between off-center positions do not effect on dynamic properties of a crystalline matrix near T C .