M. F. Kupriyanov

Composition-structure-properties dependences in solid solutions on the basis of lead-zirconate-titanate and sodium niobate

Abstract The regularities relating electrophysical and structural parameters of solid solutions on the basis of lead-zirconatetitanate and sodium niobate are considered. An important structural peculiarity of these systems is a morphotropic region (MR)-region of morphotropic phase transition between tetragonal and rhombohedral (rhombic) phases. Understanding of the considered regularities makes easier the prediction of piezoceramic composition with the given properties for different applications.

The properties of the non-stoichiometric ceramics (1-x)PbMg1/3Nb2/3O3-(x)PbTiO3

Abstract (1− x )PbMg 1/3 Nb 2/3 O 3 –( x )PbTiO 3 i.e. (1− x )PMN–( x )PT ceramics with x ⩽0.15 have been obtained and investigated. With increasing x the temperature T m increases, at which dielectric permittivity reaches its maximum ( e m ), increases the value of e m and decreases the degree of the diffuse phase transition. For x ⩽0.075 dominates electrostrictive mechanism while for x >0.075 piezoelectric effect gives a contribution into electromechanical deformation of the samples. Special attention is paid to the problem of nonstoichiometry (excess and deficit of PbO and excess of MgO).

Phase transition behavior in the morphotropic region of(x)pbtio3−(0. 98−x)Pbzro3−0. 02 (PbWO.5Cdo. 5O3

Abstract A relation between structural and electrophysical properties of (x)PbTiO3− (0.98−x) PbZrO3−0, 02 (PbWo.5Cdo.5O3) solid solution system is examined. It is found that the extent of phase transition diffuseness in the morphotropic region depends on the spontaneous deformations, phase compositions and relative unit cell volumes of the tetragonal and rhombohedral phases. The diffuseness of the phase transitions is largely determined by severity of residual local stresses at domain boundaries.

Sequence of phase transitions in PbHfO3

The temperature changes in the PbHfO3 structure in the temperature range of 20 < t < 400°C have been studied by X-ray powder diffraction. The sequence of phase changes with an increase in temperature was found to be as follows: orthorhombic phase Pbam (O1), orthorhombic phase C2mm (O2), tetragonal phase P4mm (T), and cubic phase Pm3m (C). The C2mm and P4mm phases are ferroelectric, which is confirmed by measuring the dependences ɛ(t). The similarity of the transition pattern obtained with the known transition sequences for ferroelectric (barium titanate, potassium niobate, and lead titanate) and antiferroelectric (lead zirconate) oxides is analyzed.

Piezoceramic Transducers with High Thermal Stability of the Resonance Frequency

Methods for increasing thermal stability of the resonance frequency f r of the PZT-based piezoceramic resonators are shown. An influence of ( x )PbTiO 3 content and an effect of doping ions on j f r / f r in the PZT solid solution has been considered. Correlation between qualities of the domain structure, spontaneous deformation parameters i T , i Re , degree of domain reorientation m , internal friction Q m m 1 and mechanical quality factor Q m , has been revealed. An impact of electronegativity of the doping ions on f r thermal stability have been cleared up. Ferroelectric hardness has also been considered. The piezoceramic band filters exhibiting j f r / f r <0.2% and Q m =3225 have been thus obtained.

Specific features of structural states in the BiFeO3-YMnO3 solid solutions

The (1 − x)BiFeO3−xYMnO3 solid solutions have been found to undergo the following sequence of phase transformations with increasing x: R3c → Pbnm → C2 → Pnma → P63cm. It has been established that the Pbnm and Pnma phases have different orientations of atomic displacements and can exhibit antiferroelectric properties.

Thermal dependence of pyroelectric parameters of PZT-based multi-component electroceramics

Abstract Five-component electroceramics based on solid solution PbTiO 3 –PbZrO 3 –PbNb 2/3 Zn 1/3 O 3 –PbSb 2/3 Mn 1/3 O 3 –PbNb 2/3 Mn 1/3 O 3 was studied. The chemical composition of the solid solution varied with PbTiO 3 content. Thus samples exhibiting rhombohedral crystalline structure, tetragonal structure, as well as samples exhibiting compositions from the morphotropic phase boundary region (MBR) were under investigation. Conventional mixed oxide method was used for the powder preparation. Hot pressing technique was employed for fabrication of ceramic pellets. To produce pyroelectric activity the samples underwent high voltage poling (HVP) or low voltage poling (LVP). Thermal stability of the pyroelectric coefficient was measured according to both quasi-static γ ST ( T ) and dynamic method γ D ( T ). The customised measuring system was developed. Dependence of the dielectric permittivity e 33 /e 0 of poled samples on temperature was also recorded. Results are reported and explanation of the observed temperature traces for γ ST ( T ), γ D ( T ), and e 33 /e 0 ( T ) is given taking into consideration the two different methods of poling the multi-component samples.

Influence of cyclic phase transitions on some properties of the ferroelectric perovskites

Abstract The results of investigations of the influence of cyclic phase transitions on certain properties of the ferroelectric perovskites are presented. The materials were PZT-type ceramics obtained either by hot-pressing or by classical ceramic technology. It has been found that a close relationship exists between the concentration of linear defects and the stability of the resonant frequency as a function of temperature and time. The investigated samples can be divided into two groups: samples with high initial stability of resonance frequency and samples with low initial temperature stability. Our investigations show that in this two cases it is possible to distinguish three ranges of numbers of thermocycles, but the dependencies in the two cases differ one from the other. The change of concentration of defects and their distribution inside the crystallites lead to changes of temperature stability of resonant frequency. After 5–6 thermocycles the stability increases, but if the initial stability of the resonant frequency is high the changes are too small for practical applications.

Structure and lattice dynamics of solid solutions (1 − x)BiFeO3-xANbO3 (A = K, Na)

The structures and the dynamic characteristics of the lattices of two compositions of solid solutions of multiferroic BiFeO3 with ferroelectric KNbO3 and antiferroelctric NaNbO3, namely, (1 − x)BiFeO3-xKNbO3 and (1 − x)BiFeO3-xNaNbO3, have been studied using X-ray powder diffraction and Raman spectroscopy. For these systems with x = 0.3, 0.5, and 0.7, the symmetry and unit cell parameters at room temperature have been determined. An analysis of the vibrational spectra has revealed sequences of rotational distortions with variations in the concentrations of components.

Modifying the properties of lead titanate in PbTi1 − xMnxO3 solid solutions

Spontaneous deformation in the PbTi1 − xMnxO3 system at room temperature is found to decrease as x increases, indicating a drop in the temperature of the ferroelectric phase transition.