N. V. Dergunova

Rendering barium titanate semiconductive by doping with rareearth elements

Abstract Distribution of doping cations between A and B sites of perovskite ABO3 structure obeys certain conditions derived in terms of energy. These can be applied to predict semiconducting BaTiO3-based compositions, to account for yet unexplained anomalies in concentrational dependencies of electrical resistivity and Curie temperature, and to understand the relatively unimportant effect of doping in the case of solid solutions such as Ba1−x Sr x TiO3 and Ba1−x Ca x TiO3.

New binary systems of solid solutions based on NaNbO3

The complex investigations of new and known binary systems of solid solutions (SS), based on antiferroelectrics NaNbO3 (NN) with oxides, possessing columbite. KW-bronze, ilmenite and perovskite structure as second components: (1 - x)NN - xAIINb2O6 and (1 - x)NN - xAIITiO3 (AII - Ni. Cu, Mg, Co, Zn, Cd, Mn, Ca, Sr or Pb) have been conducted. The ferro- and piezoelectric properties with a wide range of values have been detected in all systems investigated. There are solid solutions, in which the detected values of electrophysical properties make them suitable for use in piezoelectronics.

Atomic substitution effects in binary solid solution systems based upon NaNbO3

Several regular variations of electrophysical properties, which depend on substituting atoms characteristics, have been found by the use of computed and experimental characteristics of interatomic A-O and B-O bonds of solid solutions in binary systems of two types: NaNbO3-A0.5IINbO3(ANb2O6) and NaNbO3-AIITiO3) where AII = Ni, Cu, Mg, Co, Zn, Mn, Cd, Ca, (NaBi)0.5, (AgBi)0.5, Sr, (KBi)0.5, Pb or Ba. The correlations between Curie temperature, Tc, dielectric permittivity, ∊33T/∊0, piezocoefficient, d31, electromechanical coupling factor, Kp, on one hand and interatomic bond lengths A-O and B-O on the other hand have been determined.

Physical Properties of NaNbO3–A2+TiO3and NaNbO3–A2+Nb2O6Solid Solutions

Solid solutions of compounds with the ilmenite, columbite, or potassium tungsten bronze structure in the perovskite compound NaNbO3were studied. The observed property–structure–composition relations were used to choose promising compositions for designing new piezoelectric ceramics.

Ferroelectric solid solutions with high piezoelectric characteristics

Abstract It has been shown that high dielectric permittivity and piezoelectric parameters are obtainable within the PZT-related multicomponent solid-solution systems by appropriate choice of the cationic constitution, component number and concentration ranges. The role of grain size has been emphasized.

Possibilities of Isomorphous Substitutions in Lead Titanate and Lead Zirconate

The extents of iso- and heterovalent substitutions in the ferroelectric compound PbTiO3and antiferroelectric compound PbZrO3are analyzed using solubility diagrams. The possibility of predicting the solubility limits in perovskite systems is discussed.

On the possibility of isomorphic substitutions in ferroelectrics with the perovskite -and pseudoilmenite — type structure

The present paper deals with a crystallochemical analysis of the possibilities of isomorphic substitution of atoms in the ferroelectrics (Na, Li) NbO3 and LiNbO3 with a perovskite-and pseudoilmenite-type structure, respectively. As the arguments we used dimension, electronegativity, electron structure and symmetry of valent orbitals of the substituted and substituting atoms. The solid solutions (SS) of binary systems on the basis of LiNbO3 (or NaNbO3) and iso-and nonisostructural components and also the compositions of (Na, Li) NbO3 and lithium metaniobate (LMN) modified with n-valent (n = 1 - 6) elements were chosen as the objects of the present study. Diagrams of solubilities for substitutions in the A-or B-sublattice of (Na, Li)NbO3 and LiNbO3 were constructed. The original experimental results and the bibliographical data confirming the correctness of the analysis a presented.

Highly effective piezoelectric materials for various fields of application

This paper describes highly effective piezoelectric ceramic materials (developed at Rostov State University) which have a combination of parameters required in various fields of application including: materials stable to electrical and mechanical influences; materials possessing high dielectric permittivity; high sensitivity materials; materials possessing high stability of resonance frequency; materials possessing low dielectric permittivity; and high-temperature materials. A number of these materials are used in various industrial devices and instruments. A method for producing novel piezoceramic materials is considered.

On compressibility of mixed crystals possessing the perovskite structure

Abstract The compressibility β of mixed oxides possessing the perovskite-type structure has been evaluated as a function of the composition x. The conditions for different types of the β (x) dependence have been established. Specifically, it should be linear in case of isovalent substitution and may be S-shaped for heterovalent substitutions provided the compositional dependence of the average unit-cell parameter has negative deviation from Vegards law.

Data bank on properties and applications of ferro-piezoelectric materials

Work on the formation of the data bank on FPCM developed at the Institute of Physics (Rostov State University) is under way. The bank contains electrophysical, elastic structural parameters of materials, their chemical composition and technological characteristics and the fields of applications. FPCM of different groups possess various parameters: very high and extremely low values of permittivity and mechanical quality, low dielectric losses; high values of piezoelectric response; temperature stability of resonance frequency and Curie point. There is a wide spectrum of FPCM applications: low- and high-frequency devices, high sensitive and high-temperature transducers, devices with high specific power, filter devices and others. The use of the data bank will make it possible to proceed to a new step of analyzing and generalizing the results of investigations of FPCM. The analytical dependences relating the composition of materials with their properties will allow one to predict and to design materials with prescribed properties.