Stabilization of perovskite phase and dielectric properties of Pb(Zn, Mg)1/3Nb2/3O3-PbTiO3 ceramics prepared by excess constituent oxides

The perovskite phase in PZN-PMN-PT (PbZn1/3Nb2/3O3-PbMg1/3Nb2/3O3-PbTiO3) pseudoternary ceramics was stabilized by the addition of excess constituent divalent oxides (PbO, MgO, and ZnO). 5 mol% excess MgO or 7.5 mol% excess PbO was sufficient to eliminate the remnant cubic pyrochlore phase after sintering at 1100 °C for 1 h. The enhanced diffuse phase transition (DPT) and the decrease in the electrical resistivity were observed in the presence of excess ZnO or MgO. These were interpreted in terms of the additional formation of negatively charged, short-range ordered 1: 1 domains with a concomitant generation of charge carriers (holes). The behavior of excess MgO or ZnO at concentrations above 5 mol% was studied by examining complex impedance patterns.

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Relaxation behaviour of Pb(Ni1/3Nb2/3)O3 ceramics

Canadian Journal of Physics ◽

10.1139/p93-051 ◽

1993 ◽

Vol 71 (7-8) ◽

pp. 322-325 ◽

Cited By ~ 12

Author(s):

Seema Sharma ◽

R. Sati ◽

R. N. P. Choudhary

Keyword(s):

Phase Transition ◽

Diffuse Phase Transition ◽

High Dielectric Constant ◽

Pyrochlore Phase ◽

Relaxation Behaviour ◽

Dielectric Studies ◽

Solid State Reaction Technique ◽

High Dielectric ◽

A Minor ◽

Diffuse Phase

Polycrystalline samples of a cubic perovskite structure with an estimated 2.9% of a minor pyrochlore phase of Pb(Ni1/3,Nb2/3)O3 were synthesized by a high-temperature solid-state reaction technique. Dielectric studies show that the material is a good relaxor with a high dielectric constant. Diffuse phase transition through a wide Curie-temperature range was observed. The activation energy in a specified range of temperature for the material is estimated.

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Enhanced diffuse phase transition and defect mechanism of Na-doped Pb(Mg1/3Nb2/3)O3 relaxor ferroelectrics

Journal of Materials Research ◽

10.1557/jmr.1997.0221 ◽

1997 ◽

Vol 12 (6) ◽

pp. 1614-1624 ◽

Cited By ~ 14

Author(s):

Kyu-Mann Lee ◽

Hyun M. Jang

Keyword(s):

Phase Transition ◽

Electrical Conductivity ◽

Diffuse Phase Transition ◽

Short Range ◽

Oxygen Vacancies ◽

Superlattice Reflection ◽

Relaxor Ferroelectrics ◽

Defect Mechanism ◽

Defect Process ◽

Diffuse Phase

The diffuse phase transition (DPT) characteristics and the associated defect mechanism of Na-doped Pb(Mg1/3Nb2/3)O3 (PMN) relaxor perovskite were studied. The enhanced DPT and the decrease in the intensity of the superlattice reflection were observed in the presence of Na2O. These contradictory observations were interpreted in terms of the inhibition of the growth of the 1 : 1 nonstoichiometric short-range ordered domains and the increase in the microcompositional fluctuation of the B-site cations caused by the formation of negatively charged Na′Mg sites. The mechanism of the associated defect process was then elucidated by analyzing the electrical conductivity as a function of the oxygen partial pressure. It was shown that the substitution of Na+ ions for Mg2+ ions in the B-site sublattice of perovskite PMN produced the negatively charged sites with a concomitant generation of oxygen vacancies () for the ionic compensation. This expedites the enhancement of the compositional inhomogeneities of the B-site cations and suppresses the growth of the nonstoichiometrically ordered nanodomains in a disordered matrix.

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