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Herein, the properties of broadband dielectric spectra up to THz–infrared range of the (1 − x)BaTiO3‐xBaZrO3 (BZT‐x) solid solution are reviewed and complemented. This includes the proper ferroelectric (x = 0), diffuse ferroelectrics (0 < x ≤ 0.2), relaxor ferroelectrics (0.4 ≤ x ≤ 0.8), dipolar glasses (x > 0.8), and the normal dielectric (x = 1). The spectra are characterized by an overdamped central mode in the microwave range which weakens on cooling. Except for BaTiO3, the soft mode and central mode do not soften appreciably and do not contribute substantially to the low‐frequency permittivity maximum. The most important dielectric contribution is brought by Cole–Cole relaxation assigned to hopping of Ti ions in the BaTiO3 clusters, which obeys the Arrhenius law with a common activation energy for the whole relaxor range of Ea ≈ 181±17 meV and broadens on cooling as described by a temperature‐independent distribution of activation energies. It follows that the polar nanoregions within the BaTiO3 clusters remain very small with temperature‐independent size and frozen boundaries, even if the Ti ions inside them are hopping. This differs from the usual lead‐containing relaxors, in which the polar nanoregions grow on cooling and follow the glass‐like freezing. [ABSTRACT FROM AUTHOR]

High-density KTaO3 ceramics were synthesized and studied by means of microwave, terahertz, infrared, and Raman spectroscopies. The results were analyzed together with recently published radio-frequency data. [S. Glinsˇek et al., J. Am. Ceram. Soc. 94, 1368 (2011)] Three polar modes expected for the cubic structure were observed. As in single crystals, the lowest-frequency TO1 mode (soft mode) strongly softens on cooling, while the TO2 and TO4 mode frequencies do not change with temperature. The permittivity does not show any significant dispersion below the soft mode frequency and its value in the kHz and GHz range is mainly given by the intrinsic polar lattice modes contribution. The soft mode frequency agrees with the values found in single crystals; this indicates a negligible influence of the grain boundaries on the dielectric response in KTaO3 unlike in other ferroelectric or incipient ferroelectric perovskite ceramics. [ABSTRACT FROM AUTHOR]

It is well known that the cubic pyrochlore Bi1.5ZnNb1.5O7 exhibits higher permittivity and dielectric loss than monoclinic Bi2Zn2/3Nb4/3O7 due to structural disorder in the A sites of Bi1.5ZnNb1.5O7. We have studied systematically the impact of the ion substitution in the A site of monoclinic Bi2Zn2/3Nb4/3O7 on the structure and microwave dielectric properties. It is shown that the structure and permittivity of (Bi1.92M0.08)(Zn0.64Nb1.36)O7 (M=Zn,Ca,Cd,Sr,Ba) ceramics remain almost the same as in Bi2Zn2/3Nb4/3O7; only the Ba substituted ceramics have higher permittivity due to multiphase structure. Microwave dielectric properties were compared with complex dielectric response in terahertz and infrared frequency range of 0.1–100 THz, which allows us to estimate intrinsic and extrinsic contributions to microwave dielectric losses. The best microwave properties were obtained in (Bi1.92Ca0.08)(Zn0.64Nb1.36)O7 with [variant_greek_epsilon]=76, Qf>=5000 (sintered below 950 °C), which is promising for microwave low temperature cofiring ceramic application. [ABSTRACT FROM AUTHOR]

Cubic pyrochlore (Bi1.5Zn0.5)(Zn0.5-x/3TixNb1.5-2x/3)O7 ceramics with 0<=x<=1.5 were synthesized and investigated between 100 Hz and 100 THz by means of broadband dielectric spectroscopy, time-domain terahertz transmission spectroscopy, Fourier transform infrared reflectivity spectroscopy and Raman scattering. Bi1.5ZnNb1.5O7 exhibits a microwave dielectric relaxation which slows down and broadens remarkably on cooling. Careful structural investigations confirmed that the relaxation originates in hopping of disordered Bi and part of Zn atoms in the A sites of the pyrochlore structure. Substitution of Ti atoms to the B sites, i.e., increasing x, results in an increase of the microwave permittivity from 150 to 200 of the relaxation frequency and also of the microwave quality Q. Low temperature Raman scattering experiments did not reveal any phase transition in the samples under study. [ABSTRACT FROM AUTHOR]

Presents a study that investigated the effect of ionic parameters on the dielectric properties of perovskite ceramics. Influence of ionic structure on the dielectric permitivity of the samples; Correlation between ionic mass and size and dielectric properties; Investigation of the effective charge and polar-phonon mode parameters.

Presents a study that evaluated the correlations between ionic parameters and the microwave dielectric properties of perovskite ceramics using dielectric spectroscopy. Analysis of the permitivity of the samples; Examination of the dielectric loss of the samples; Correlation between frequency and permitivity of the samples.

Recently we have demonstrated that out-of-plane dielectric properties of polycrystalline SrTiO3 (ST) films depend on the strain/stress induced by the substrates due to thermal expansion misfit. Here, we present a complementary infra-red (IR) spectroscopy investigation of the role of Al2O3 and MgO substrates on the lattice dynamics and in-plane dielectric properties of ST thin films also prepared by sol-gel. We verify that ST films deposited on Al2O3 substrates, being under a tensile stress, present the soft mode behaviour similar to that of ST single crystals, deviating just below 150 K. In contrast, ST films deposited on MgO substrates, being under compressive stress, have higher soft mode frequency from 10 to 300 K. It is thus proved that for polycrystalline ST films the intrinsic in-plane relative permittivity may be tuned through an induced stress state. [ABSTRACT FROM AUTHOR]