D. Dmytrow

Dielectric, pyroelectric, and thermally stimulated depolarization current investigations on lead‐lanthanum zirconate‐titanate‐x/95/5 ceramics with La content x=0.5%–4%

It is shown that La dopants have a strong influence on the antiferroelectric‐ ferroelectric‐paraelectric (AFE‐FE‐PE) phase transitions and properties of the lead‐lanthanum zirconate‐titanate‐x/95/5 ceramics (with La contents x=0.5%–4%). The occurrence of the ferroelectric microdomains, dispersed in the AFE and PE matrices, gives rise to properties typical for ferroelectric relaxors. The space‐charge concentration polarization, formed by some mobile ion defects, plays an important role in this behavior. This space‐charge polarization and its interaction with the spontaneous polarization was investigated by dielectric, pyroelectric, and thermally stimulated depolarization current measurements. A qualitative model of interpretation is discussed.

Phase composition and dielectric properties of lead barium zirconate solid solutions

Abstract Results are presented of X-ray analysis and also dielectric and pyroelectric studies on (Pb1−x Ba x )ZrO3 (x ≤ 0.25) solid solutions. The coexistence of A, F and P phases in the vicinity of phase transition temperatures was determined and correlation between phase composition of samples with various Ba content and the form of spontaneous polarization versus dopant concentration function was established. It was also ascertained that on the both sides of transient ferroelectric phase there exist ferroelectric microdomains responsible for ferroelectric relaxor type behavior of (Pb1-x Ba x )ZrO3 solid solutions and that Ba content markedly influences these properties.

Raman investigation of undoped, niobium‐doped, and lanthanum‐doped lead zirconate‐titanate ceramics

In a previous article, we proved and characterized a phase transition of an order‐disorder type, below room temperature, in the Pb1−3X/2LaX⧠X/2(Zr0.95Ti0.05)O3 (X=0.5–4 wt % La) ceramics. In the present article, the analysis of this order‐disorder transition is continued on the basis of the comparative study of Raman scattering, as a function of the Nb or La dopant. The parallel analysis and the interpretation of the Raman spectra of the nondoped, Nb‐doped, and La‐doped Pb(Zr0.95Ti0.05)O3 ceramics lead to new information concerning the identification of the vibrational modes involved. In addition, the correlation between the phase transitions and the nature of the dopants is established. New information concerning the cell doubling, during the ferroelectric low temperature to ferroelectric high temperature phase transition, is obtained as well. The Raman study of the lead‐lanthanum zirconate‐titanate ceramics allowed us to identify for the first time the so‐called ‘‘antiferroelectric mode’’ and ‘‘ferroele...

Structure and electrical properties of PbZrO3 doped with Nb2O5

Results are presented of complex studies on the structural, dielectric and pyroelectric properties and also on the electrical conductivity and Seebeck effect in samples of ceramic PbZrO3 + x Nb2O5 (where 0 < x ≤ 2% mol). Marked variations in these properties were observed when the concentration of Nb2O5 became greater than 1.2% mol. It was ascertained that this is connected with the creation of a large number of vacancies in the Pb sublattice.

Raman scattering investigation with temperature of the phase transitions in (Pb0.825Ba0.175)ZrO3 and (Pb0.65Ba0.35)ZrO3 ceramics

Abstract Raman scattering investigations of lead-barium zirconate are presented for two barium concentrations, as a function of temperature from 10 to 450 K. An order-disorder phase transition is observed at 130 K for the low barium concentration, for which an antiferroelectric-ferroelectric phase transition is equally observed at 308 K and a ferroelectric-paraelectric one at 433 K. The ceramic containing a high barium concentration is in a ferroelectric state up to 403 K, above this temperature begins the paraelectric phase of the material. The order parameters of the two types of transitions, order-disorder and antiferroelectric-ferroelectric, are evaluated.

Phase transitions in ceramic AgNbO3 investigated at high hydrostatic pressure

The influence of hydrostatic pressure on dielectric permeability in ceramic AgNbO3 as function of temperature was studied. Parameters T0, C, p0, C* and Qh were determined. It was ascertained that phase transition temperatures T1 and T2 shift towards lower temperatures at the rates of dT1/ dp = -30 ± 3 K/GPa and dT2/dp = -37 ± 6 K/GPa while T3 and T4 shift towards higher temperatures at the rates of dT3/dp =28 ± 7K/GPa and dT4/dp = 58 ± 9K/GPa. The possibility of existence of ferroelectric phase up to T3 = 610 K is discussed.

Low-frequency dielectric dispersion in PbZrO3 with oxygen vacancies

The dielectric response in the 0.1-20 kHz frequency range in single crystal and ceramic samples of lead zirconate was studied. Strong relaxational dielectric dispersion was observed in the high temperature range. Intensity of this dispersion was found to be markedly dependent on concentration of oxygen vacancies.

Dielectric and raman studies of Ta doped lead zirconate

Abstract The influence of introducing small amount of Ta ions (from 0.2 to 2% mol.) in pure PbZrO3 ceramics is studied by dielectric and light scattering measurements. No influence is detected on the phase transition sequence and temperatures. Increase of Ta dopants leads to gradual vanishing of remanent polarization and diffuse character of the transition. The results are analyzed in terms of charge compensation effects due to vacancies in the Pb-sublattice.

The structure and dielectric properties of pb(zr1−xhf x )o3 (x≤0.05) solid solutions

Abstract Structural and dielectric investigations on ceramic Pb(Zr1−xHf x )O3 solid solutions with Hf content up to 5 mol % are reported. The intermediate ferroelectric phase in a narrow temperature range below the Curie point was observed. The phase transitions FE-PE and FE-AFE are diffused.

DiC9: Modification of the relaxor properties of PLZT-1/95/5 by thermal and electrical treatment

Abstract Dielectric, pyroelectric, thermally stimulated current and optical measurements have been performed on PLZT 1/95/5 semitransparent ceramics. The temperature dependence of these properties was studied in the vicinity of the phase transitions between the antiferro- ferro- and paraelectric phases. Some indication of relaxor behaviour of these ceramics was confirmed in wide temperature ranges around these transitions, particularly at the AFE-FE one. It has been shown that the relaxor behaviour can be modified by suitable thermal and electric treatment.