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Iron-enriched ferroelectrics are of particular interest as piezoactive components of piezoelectric-ferrite ME ceramics. This is due to the phase composition similarity and the reduction of expected interfacial doping effects during high-temperature calcination. This idea seems attractive, but laborious due to the significantly limited number of possible piezoelectric–ferrite combinations. Therefore, there is practically no data on such systems in the literature. ME composite ceramics based on the highly efficient Fe-containing Pb(Fe 0.5 Nb 0.5) 0.935 Ti 0.065 O 3 (PFNPT) ferroelectric has been studied. (100-х) wt.% Pb(Fe 0.5 Nb 0.5) 0.935 Ti 0.065 O 3 (PFNPT) + х wt.% Ni 0.9 Co 0.1 Cu 0.1 Fe 1.9 O 4-d (NCCF) composite systems has been obtained by the solid-state method at 1050 °C, with no foreign phases. The specimens densities amounted to ∼80% of the theoretical. It has been shown that the ME conversion efficiency and other composites properties are significantly influenced by the PFNPT precursor pre-treatment method. The maximum value of the ME coefficient ΔΕ/ΔΗ = 75 mV/(cm Oe) has been observed for specimens with x = 50–60 made from PFNPT powder with the addition of Li 2 CO 3. An increase in the ME composites sintering temperature to 1150 °C leads to the formation of Pb 2 Nb 2 O 7 foreign phase with a pyrochlore structure along the grain boundaries. The ME coefficient ΔΕ/ΔΗ does not exceed 15 mV/(cm⋅Oe). There is an threefold decrease in the composites piezoelectric parameters (piezoelectric coefficients d ij , g ij), as well as in their magnetic properties (magnetizations M S , M R) due to piezophase degradation, which is presumably associated with a change in the cations distribution over A and B sublattices of the spinel structure. [ABSTRACT FROM AUTHOR]

The effect of magnetoactive cations on the stability and properties of Aurivillius phases (1) Bi5Ti2(TiFe)1−x(NiNb)xO15, (2) Bi4Ti3−2.5x(Nb1/2Fe1/2)x(Nb2/3Ni1/3)1.5xO12, (3) Bi3Ti1−2.5xNb1+1.5x(Fe1/2Ni1/2)xO9, (4) Bim+1Fem−3Ti(3−x)(Ni1/3Nb2/3)xO3m+3 has been investigated. The range of existence of solid solutions was found to be limited to the values of x = 0–0.10 (1), 0–0.3 (2), and 0–0.2 (3). Although the solid solutions exist in the whole concentration range studied (x = 0–0.07) in the series (4), the stability is limited to the value of m = 6–7. The unit cell volumes increase with increasing x, which is expected due to the ionic radii of the dopant cations that are larger than those of the substituted cations. The coexistence of piezoelectric and magnetic properties was observed in the samples of solid solutions (1) and (4): the values of the piezoelectric coefficient d33 and piezoelectric voltage coefficient g33 reach 7 pC/N and 3.5 mV m/N, respectively; the saturation magnetization Ms and remanent magnetization Mr increase with increasing x, while the coercivity remains almost unchanged. Thermal studies indicate phase transitions in Bi5Ti2(TiFe)1−x(NiNb)xO15, and Bim+1Fem−3Ti(3−x)(Ni1/3Nb2/3)xO3m+3 at ~ 300–400, 750 and 840 °C. Additionally, these samples demonstrate a magnetodielectric effect of up to ~ 50% when applying a DC magnetic field of ~ 1 T in the temperature range of ~ 340–350 °C that is supposed to be a ferromagnetic Curie point. [ABSTRACT FROM AUTHOR]