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Temperature dependence of the optic phonons in 0.4PbMg 1/3 Nb 2/3 O 3 –0.3PbSc 1/2 Nb 1/2 O 3 –0.3PbZn 1/3 Nb 2/3 O 3 (0.4PMN–0.3PSN–0.3PZN) ceramics were studied by means of FTIR reflection and THz transmission spectroscopy in the temperature range of −253.15 to 226.85 °C. On heating from low temperatures, the A 1 component of the strongly split TO 1 mode softens towards the Burns temperature, but the softening ceases near 126.85 °C which could be a signature of polar cluster percolation temperature. Surprisingly, the TO 2 mode also softens on heating and follows the Cochran law with extrapolated critical temperature close to the melting point.

The microwave dielectric, Bi 1.5 ZnNb 1.5 O 7 exhibits low-temperature dielectric relaxation. To find the origin of the dielectric relaxation of Bi 1.5 ZnNb 1.5 O 7 , we studied the structure and dielectric behavior of Bi 1.5 ZnNb 1.5 O 7 in detail. The Bi 1.5 ZnNb 1.5 O 7 is not composed of a single phase pyrochlore structure. Instead, it consists of unusual structure of Bi 1.5 Zn 0.92 Nb 1.5 O 6.92 and ZnO. The ZnO is distributed evenly in the grain and at the boundary of the Bi 1.5 Zn 0.92 Nb 1.5 O 6.92 structure. Many small voids (

Microwave dielectric properties of fluorite-like (1 − x )Bi 2 O 3 – x Nb 2 O 5 solid solutions with various x between 0.1 and 0.26 are compared with complex dielectric response in THz and infrared frequency range between 0.1 and 100 THz, which allows the estimation of intrinsic and extrinsic dielectric losses. The best quality sample with the most attractive properties was found for x = 0.26 composition with the permittivity of 86, Qf = 1000 GHz and τ f = 120 ppm/K. Our ceramic system exhibits two different crystal structures depending on Nb 2 O 5 concentration and it is shown how the infrared reflectivity spectra can help to distinguish the structures. τ f can be reduced to zero by mixing of Type II and Type III structures.

The aim of this work was to prepare phase pure and dense EuTiO 3 ceramics and to establish their infrared reflectivities. Two kinds of stoichiometric powder mixture (Eu 2 O 3 + Ti 2 O 3 and Eu 2 O 3 + TiO 2 ) were used as precursors for shaping green bodies by cold isostatic pressing. Dense bulk samples were prepared by pressure-less sintering in reducing (Ar + 7%H 2 , 100%H 2 ) conditions in a temperature range of 1300–1650 °C. The sample prepared from Eu 2 O 3 + TiO 2 powder mixture sintered in pure hydrogen at a temperature of 1400 °C for 2 hours exhibited a relative density higher than 95%TD and 100% phase purity, which resulted in its high infrared reflectivity affected by neither low density nor phase impurities.

Inelastic neutron scattering on deuterated BCCD revealed a transverse acoustic branch of Λ3 symmetry coupled to a soft polarisation branch Py(k) of same symmetry. As the transition to the incommensurate state is approached from above (T>T1 = 164 K), the lowest-frequency branch develops a broad dispersion minimum near k =0.32c ∗ . The soft mode is observed as an underdamped excitation down to 170K. The present results establish the displacive nature of the phase transition at T1 and the P y- symmetry of the primary order parameter. A semi-quantitative scheme for the 14 lowest phonon branches along the c∗ direction, in the normal phase, is suggested, based on the available neutron-scattering, infrared, Raman, and acoustic data.

Changes of the properties of semiconducting GaAs crystals by N-implantation (under different implantation and annealing conditions) studied by IR (localized vibrational modes, absorption edge tails) and Raman spectroscopies are reported. Broad LVM at ∼ 470 cm −1 was observed in agreement with (refs. 1,2). Band at 582.5 cm −1 was found on samples implanted with high current density (10 μA cm −2 ). Nitrogen, incorporated most probably into the As-vacancy, in doses ⩾10 16 cm −2 orders the network.

The IR reflectance of several YBCO single crystal films was measured with a special emphasis on anisotropic (110) films. Whereas for the E⊥c polarization only a small temperature dependence was detected for the E∥C polarization much more pronounced temperature dependence below Tc enabled us to determine the superconducting gap energy 2△c ≅ 3.2 kTc. It is confirmed that in the previous IR measurements on polycrystalline samples the E∥c response dominated both in the phonon peak structure as well as in temperature dependences of the reflectivity.