Solid Solution Pb Research Articles

Synthèse et caractéristiques cristallographiques des phases solides de type fluorine des systèmes PbF 2 LnF 3

A preliminary study of the PbF 2 LnF 3 systems ( Ln = lanthanides and Y) has allowed the characterisation of three phases: a disordered fluorite-like solid solution Pb 1− x Ln x F 2+ x the domain of which increases with increasing temperature and dopant ion radius, and two anion-excess fluorite related superstructures: Pb 2YF 7 (tetragonal, space group I4 or I4 m , a # a F √2 , c # 3a F ) and Pb 4 Ln 3F 17 with Ln = SmLu (rhombohedral, space group R3, a h # ( a F √2 )√7, c h # 2a F √3 ). The crystallographic characteristics of the two ordered phases have been confirmed by electron diffraction.

Phase equilibrium and ionic conductivity in the PbF 2YF 3 system

The phase diagram of the PbF 2-YF 3 system has been studied by D.T.A. and X-ray diffraction techniques. A large domain of a fluorite-type solid solution Pb 1−xY xF 2+x (0⩽x⩽0.39 at 885°C) called F has been isolated. A very small domain of a tysonite-type solid solution H only stable in a very narrow temperature range is also observed. Two ordered phases R and T, whose structures derive from the fluorite-type are identified. The transport properties of F, R and T are analyzed and compared to those of analogous phases belonging to other Pb 1−xM xF 2+x systems (M = In, Sb, Bi). The influence of the polarizability of the substituent trivalent ion on the electrical properties is particularly discussed.

Etude des proprietes de conductivite ionique des phases appartenant au systeme PbF 2-InF 3

A detailed study of the transport properties of the disordered fluorite-type solid solution Pb 1-xIn xF 2+x (0 < × < 0.25) and of the ordered fluorite-type related Pb 2InF 7 (x = 0.333) and Pb 7In 5F 29 (x = 0.417) has been carried out. For x = 0.25 the conductivity is shown to decrease when disordering diminishes as a consequence of annealing. The disordered Pb 0.88In 0.12F 2.12 phase is a fairly good anionic conductor.

Piezoelectric properties of polycrystalline ferroelectrics in the low temperature region

Abstract In this paper regularities in the change of piezoelectric properties in polycrystalline ferroelectrics of the lead zirconate titanate system (PZT) when they are cooled down to the temperature of 4.2 K are considered. Exposure to weak and strong electric fields and to mechanical stresses has been studied. A system of solid solutions Pb(Zr x Ti1-x )O3 + yMnO2 where 0.3 ≤ x ≤ 0.7, 0 ≤ y ≤ 3% has been our object of investigation, however, the revealed relationships have a more general character and apparently exist in other solid solution systems on the PZT basis as well as, to a large extent, in polycrystalline ferroelectrics in general.

Piezoelectric Ceramics Used for Thickness Shear Mode and Their Applications

Solid solution Pb[Zr, Ti, (Mn1/3Sb2/3)]O3 ceramics with small amounts of metal oxides show large electromechanical coupling factors (>0.5), high mechanical Q factors (>1000), small temperature coefficients of frequency constant (<±10 ppm/°C) and low aging rates of frequency constant (<0.01%/time decade) in regard to thickness shear vibration mode. It was confirmed that 1st and 2nd order group PCM timing tank ceramic filters, as well as the direct-to-line FDM bandpass ceramic filter and the channel bank mechanical filter, using thickness shear resonators made of the above ceramics, have sufficiently good performances and stabilities for practical use.

Etude par diffraction de neutrons de la solution solide Pb 1−1xTh xF 2+2x

Bragg neutron diffraction studies have been carried out on the fluorite type solid solutions Pb 1−xTh xF 2+2x (0 < × < 0.25). The distribution of fluorine atoms between normal and interstitial sites as a function of the substitution rate is given. A volume of presence has been determined for interstitial anions. Electrical and structural data are correlated. Two conductivity mechanisms are proposed according to the fact that the pathway is free or blocked up. The best electrical performances are obtained for Pb 0.875Th 0.125F 2.25, which corresponds to a maximum of vacancies.

Conductivite anionique des phases appartenant au systeme PbF 2  ZrF 4

The transport properties of the disordered fluorite-type solid solution Pb 1−xZr x F 2+2x (0 < x ⩽ 0.18) and of the ordered compounds of formulations Pb 5ZrF 14 (x = 0.167), Pb 3ZrF 10 and PbZrF 6 have been studied. The disordered phase Pb 0.90Zr 0.10F 2.20 is a fairly good anionic conductor. For x = 0.167, the disordered phase is shown to be a better conductor than the ordered one.

Conductivite anionique des phases du systeme PbF 2 | SbF 3

A solid solution Pb 1−xSb xF 2+x (0 < x ≤ 0.40) of fluorite type and a definite Pb 2Sb 3F 13 phase have been obtained at 250°C in the PbF 2|SbF 3 system. The study of the variation of the ionic conduction shows that Pb 0.75Sb 0.25F 2.25 is a good ionic conductor.

Etude par diffraction de neutrons de la solution solide Pb 1− xBi xF 2+ x: Correlations entre structure et conductivité ionique

Bragg neutron diffraction studies have been carried out on the fluorite-type solid solutions Pb 1− x Bi x F 2+ x (0≤ x ≤0.50). The distribution of fluorine atoms between normal and interstitial sites as a function of the substitution rate is determined. Electrical and structural data are correlated. These results are compared with those obtained from the Ca 1− x Y x F 2+ x solution.

Crystallographic and Dielectric Properties of Pb(Mg1/2W1/2)O3–BiFeO3 Solid Solutions

Solid solutions of Pb(Mg1/2W1/2)O3–BiFeO3 were investigated for crystallographic and dielectric properties. A new pseudocubic perovskite phase was found, and was tentatively indexed as cubic with the same unit cell (multi-perovskite-cell of 2×2×2) as Pb(Mg1/2W1/2)O3 in cubic phase, but with dielectric properties characteristic of a ferroelectric substance. The Curie point in this series of solid solutions has minimum of about -95°C at a composition of about 0.88Pb(Mg1/2W1/2O3–0.12BiFeO3, which lies on the boundary between the orthorhombic (pseudo-tetragonal) antiferroelectric and the pseudo-cubic ferroelectric phases.

Etude des proprietes de conductivite anionique des solutions solides Pb 1−xTh xF 2+2x

Two solid solutions Pb 1−xTh xF 2+2x of fluorite and of tysonite types (0 ⩽ x ⩽ 0.25 and 0.40 ⩽ x ⩽ 0.50 respectively) have been prepared in the PbF 2 – ThF 4 system. The study of the ionic conduction shows that they are good ionic conductors.

The relaxation time study by Shubnikov-De Haas effect in Pb 0.82Sn 0.18 Te narrow band-gap semiconductors

The nature of broadening of the Landau levels in Pb 0.82Sn 0.18Te on the basis of recent experimental data is discussed. One needs to take into account the dependence of the monotonic part of magnetoresistance on the magnetic field H to determine the Dingle temperature on the Shubnikov-de Haas data. The Dingle temperature in solid solutions of Pb 0.82Sn 0.18Te is large ( T D =2.2−24.8 K) and depends on H. The T D ( H) dependence is explained of the transition to quantum limit. In this case the relaxation time  D =ℏ( πkT D ) −1 is increased with rising of the magnetic field, which is in accordance with the theory of Abrikosov. The  D / 0 dependence on carriers concentration can explain scattering on short range potential supposing the total scattering cross-section to be S T∼ϵ −1 2 . It was shown that the presence of random fluctuations of crystal potential in the solid solution is the most possible reason of broadening of the quantum levels. The experiment supports the dependence T D ∼ √ n obtaining theoretically. cally.

Electric properties in solid solutions of Pb(ZrxTi1-x)O3 near the morphotropic phase boundary

A characteristic property of these solid solutions is the existence of an almost temperature-independent phase boundary at x ≈ 0.53 which separates a rhombohedral Zr-rich phase from a tetragonal Ti-rich phase.1,2

A study of the solid solutions Pb yMo 6X 8−xX′ x and Mo 6X 8−xX′ x (X, X′ = S, Se, Te) and their superconducting properties

The solid solutions Pb yMo 6X 8−xX′ x and Mo 6X 8−xX′ x (X, X′ = S, Se, Te) are studied and it is shown that there are correlations between T c and certain structural parameters.

Sur de nouvelles phases oxyfluorees derivees du niobate de plomb: Etudes cristallographique et dielectrique

The solid solution Pb 2−xNa xNb 2O 7−xF x obtained by substitution of oxygen by fluorine in the ferroelectric oxide Pb 2Nb 2O 7 has the cubic pyrochlore structure for 0, 75 ⩽ x ⩽ 1, 85 and monoclinic deformations of this structure for other values of x. The temperature and frequency variations of the dielectric constant and of the dielectric losses have been studied. The high values of ε′ r have been attributed to a mechanism of ionic polarizability, and those of tan δ to the mobility of the F − ions.

X-ray study of the PZT solid solutions near the morphotropic phase transition

In the solid solutions Pb(Zr x Ti 1− x )O 3 it is stated that for x ≅ 0.55 there is a morphotropic phase change. Thermodynamically, it is expected that there will be a region of x, in which the two phases coexist and obey the leverage law. By X-ray diffraction, we found that the two phases coexist for x between 0.49 and 0.64. In this range the lattice parameters do not change, and the leverage law is obeyed. We conclude that an adequate explanation of the particular properties of the PZT solutions has to be found.

Ferroelectric variable capacitors

Abstract The perovskite-like ferroelectric solid solutions (Pb, Sr)TiO3, BaTiO3-Pb(Fe1/2 Ta1/2)O3, PbO-MgO-Nb3O5 have been investigated. The electrical properties of the ceramics were measured in the temperature range -60-+100°C at a d.c. biasing field from 0 to 7 kv/mm and frequencies of 1 kc and 1.5 mc. Some solid solutions of the studied systems have diffuse phase transitions. These have high non-linearity of the dielectric constant at d.c. biasing electric fields and a high temperature stability of the dielectric constant. Some compositions of the system PbO-MgO-Nb2O5are the most useful as thermostable ferroelectric variable capacitors.

Thermodynamics of ferroelectrics with the structure of the K-W-bronze

A classification of ferroelectrics with the structure of the tetragonal K-W-bronze type is introduced. A thermodynamic treatment of their dielectric and piezoelectric properties is carried out. The conditions for the existence of a morphothropic phase boundary are discussed for the solid solutions (Pb, Ba)Nb2O6 where this boundary separates the concentration region of the tetragonal ferroelectric phase from the region of the orthorhombic ferroelectric phase.

Study of perovskite-type compounds by the method of perturbed angular correlations

The time differential angular correlation measurements have been made as a function of temperature for Hf-doped (1 mol.%) BaTiO3, SrTiO3 and for solid solutions Pb(Zr1-xHfx)O3. Results for ferroelectric phases of BaTiO3 and antiferroelectric phase of PbZrO3 are in qualitative agreement with the published data. The fairly strong internal electric field gradients have been established in the cubic phases of all materials studied. It has been shown that the main reason for these residue gradients is not the impurity effect but probably atomic thermal vibrations related to the low-frequency lattice modes of ferroelectric materials.

Thermodynamic theory of the morphotropic phase transition tetragonal-rhombohedral in the perovskite ferroelectrics

We show that the use of the Landau-Devonshire theory of the perovskite ferroelectrics permits explanation of the main features of the morphotropic phase transition in the ceramic solid solutions Pb(Zr, Ti) O 3: the maximum of the dielectric constant and the ease with which the solutions can be poled, which results in a maximum of the polarization and a maximum of the coercive field. These two properties explain the maximum of the piezoelectric activity.