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The structure and electric properties of (0.9-x)Bi(Mg1/2Ti1/2)O3-xPbTiO3-0.1BaZrO3 (0.45 ≤ x ≤ 0.53) ceramics were investigated. The morphotropic phase boundary between tetragonal ferroelectric and pseudo-cubic relaxor phases is ascertained at x = 0.50. The BaZrO3 substitution can much reduce the coercive field of Bi(Mg1/2Ti1/2)O3-PbTiO3. The studies on temperature dependence of both ferroelectric and dielectric constant indicate a direct evidence for the antiferroelectric relaxor phase, which was ever suggested in the binary system of Bi(Mg1/2Ti1/2)O3-PbTiO3. The phase transition of ferroelectric to antiferroelectric relaxor produces the thermal depoling below the Curie temperature. The ceramic of BMT-0.47PT-0.1BZ exhibits a high strain 0.37% and a large-signal d33 (530 pm/V) in the antiferroelectric-relaxor phase. BaZrO3 substituted Bi(Mg1/2Ti1/2)O3-PbTiO3 shows an analogous phase diagram to that of lead-free (Bi, Na)TiO3-BaTiO3. [ABSTRACT FROM AUTHOR]

Synchrotron radiation-based anomalous dispersion X-ray powder diffraction (ADSPD) was carried out to reveal the Pb/Bi ordering/disordering states in a series of PbTiO3-based negative thermal expansion materials (1 −x)PbTiO3−xBiFeO3 (x = 0.1, 0.3, 0.5) and (1 −x)PbTiO3−xBi(Zn1/2Ti1/2)O3 (x = 0.1, 0.2, 0.3). It gives strong evidence of the disordered Pb/Bi distributions in these compositions, which is consistent with electron diffraction studies. Combined with binding energy calculation, we show that the disordered nature of Pb/Bi distributions is likely to be attributed to the similar electron configurations of Pb2+ and Bi3+ as well as their comparable coordinate environments in perovskite structures. The results of this study may be helpful to better understand the structure–property relationship in Pb/Bi-containing perovskites and are useful for further developing underlying physics in relevant materials. [ABSTRACT FROM AUTHOR]

The use of mesoporous and hollow structures is a promising strategy to enhance gas-sensing properties. The framework of perovskite oxides has the ability to accommodate different cations, which endows it with rich oxygen deficiencies for preferable gas adsorption. Herein, we outline the fabrication of perovskite Nd1- xCa xFeO3 ( x = 0, 0.3) hollow core-shell microspheres by using carbonaceous microspheres as templates. The gas-sensing properties of Nd0.7Ca0.3FeO3 core-shell microspheres were systematically investigated. The response to 500 ppm ethanol was 17 at 140 °C, which is much higher than the response of Nd0.7Ca0.3FeO3 nanoparticles. Also, rapid response and recovery characteristics were achieved. Furthermore, after 50 cyclic tests and 10 testing days, the gas response of the Nd0.7Ca0.3FeO3 hollow core-shell microspheres to 500 ppm ethanol at 140 °C was nearly constant. The long-term stability, good sensitivity, and rapid response and recovery times demonstrate the potential application of these hollow core-shell microspheres as a sensing material. [ABSTRACT FROM AUTHOR]

Abstract: Extra large Alkaline-earth Sr2+ cation was successfully introduced into the B′-site of the complex perovskite A(B′1/3B″2/3)O3 by a molten salt synthesis method. The crystal structure of the as-synthesized Ba(Sr1/3Nb2/3)O3 was determined by Rietveld refinement of X-ray diffraction and Raman spectrum. The results showed that the as-synthesized Ba(Sr1/3Nb2/3)O3 had the 1:2 order–disorder trigonal perovskite structure, which was also an isometric compound of hexagonal BaTiO3-type structure Ba3SrNb2O9. The measured dielectric properties on the perovskite Ba(Sr1/3Nb2/3)O3 ceramics showed the good frequency stability and the low dielectric loss. [Copyright &y& Elsevier]

Review: 97 refs. [ABSTRACT FROM AUTHOR]