[en] The polycrystalline complex compounds of (Pb_zEr_1-z)(Zr_0.60Ti_0.40)_1-z/4O₃(z = 0.07, 0.08, 0.10)(PEZT) were synthesized using the metal-alkoxide sol-gel technique. Powder X-ray diffraction (XRD) studies of these compounds suggest that they can be formed in single-phase perovskite structure by a one-step process at a relatively low temperature. Scanning electron microscopy (SEM) analysis shows that the grains are nearly spherical and distributed uniformly in the compounds. Detailed studies of dielectric properties (ε, tandelta, and σ) of the compounds as a function of temperature show a broadening of the permittivity peak and a change in transition temperature with the increase of ER³⁺ concentration. Analysis of the diffusivity γ indicates the greater disordering of the system. The hysteresis loop study confirms the phase transition of the system is of second order

[en] Single phase orthorhombic tungsten-bronze (OTB) ceramics of Pb₂Bi₃NdTi₅O₁₈ (PBNT) were prepared by a high temperature solid-state reaction method. Electrical impedance, phase angle, dielectric constant and dielectric loss have been measured in the frequency range 0.1 kHz-3 MHz in the temperature region 16-250 deg. C. Dielectric studies show relaxor behaviour with a diffuse phase transition having diffusivity parameter value 1.85. AC impedance analyses suggested the phase element to be capacitive. The Cole-Cole plot indicated high resistance of the sample at room temperature. The activation energy (E_a=0.63 eV) has been estimated from the temperature variation of DC resistivity

[en] Polycrystalline samples of [Pb_0.92(La_1-zBi_z)_0.08][Zr_0.60Ti_0.40]_0.98O₃ (z=0.0, 0.3, 0.6, 0.9, 1) (PLBZT) were synthesized using a high-temperature solid-state reaction technique. The formation of the PLBZT compounds in a particular crystallographic phase as a function of Bi concentration was checked through X-ray diffraction (XRD). S.E.M. study of PLBZT with higher magnification and resolution shows the uniform distribution of particles/grains on the surface of the samples. Dielectric constant and tangent loss of the samples in wide temperature and frequency range provided the nature of phase transition. The diffuse phase transition was observed for higher z. An increase in permittivity maxima temperature (i.e. the transition temperature) was also observed with increasing Bi concentration. The values of resistivity of all the samples are very high (10⁹ Ω-cm)

[en] The nanocrystalline Pb_1-xGd_x(Zr_0.53Ti_0.47)_1-x/4O₃ (where x=0.04, 0.08 and 0.12) (PGZT) has been synthesized by a high-energy ball milling (mechanical activation synthesis) followed by sintering. The nanocrystalline PGZT obtained by this route has exceptionally high dielectric constant. X-ray diffraction studies showed that PGZT has tetragonal structure at all the compositions studied. Detailed studies of dielectric properties of PGZT as a function of temperature show a non-relaxor type ferroelectric diffused phase transition

[en] The Eu-modified Pb(SnTi)O₃ ferroelectric ceramics with a general formula (Pb_1-xEu_x)(Sn_yTi_1-y)_1-x/4O₃ (PEST) (for x=0, 0.05, 0.07, 0.1 and y=0.45) have been synthesized by a high-temperature solid-state reaction technique. Preliminary X-ray diffraction (XRD) analysis and detailed temperature and variable frequency dielectric measurements were carried out on prepared samples. The electrical conductivities (ac and dc) of the PEST compounds have been investigated and the activation energies (E_ac and E_dc) were calculated. From the XRD study, it is confirmed that the compounds have been formed in an orthorhombic single phase. Dielectric study of these compounds as a function of temperature suggests that with increase in concentration of Eu³⁺, the permittivity maximum decreases and the transition temperature shifts towards higher temperature side. It is observed that for each concentration of Eu the dielectric permittivity (ε) reaches its maximum value at the same Curie temperature for all the three frequencies, revealing the non-relaxor ferroelectric behavior of the materials

[en] The present work reports the synthesis and characterization of the ilmenite-type rhombohedral structured CoTiO_3 ceramic. The polycrystalline powder of CoTiO_3 was prepared by the mixed-oxide technique. X-ray structural analysis of the compound confirmed the formation of a single-phase compound. The study of microstructure by scanning electron microscopy shows that the compound has well defined grains which are distributed uniformly throughout the surface. It shows that the grain size lies in the range of 8–10 μm. The Fourier transform infrared spectroscopy (FTIR) studies confirm the presence of Ti−O, Ti−O−Ti, Ti−O−O, Co−O bond in the studied compound. The frequency dependence of dielectric constant was explained on the basis of Maxwell–Wagner mechanism and Koop's phenomenological theory. The frequency-temperature dependence of impedance analysis shows that the bulk effect dominates up to 250 °C, and the appearance of second semicircular arc above 280 °C indicates the presence of grain boundary effect in the sample. The depressed semicircles in Nyquist plot with depression angles clearly indicate the distribution of relaxation times in the ceramic samples. It also shows that the material has negative temperature co-efficient of resistance similar to that of semiconductors. Similar behavior has also been observed in the study of I−V characteristics of the material. Through the study of dc conductivity of CoTiO_3 and using the relation; ln σ_d_c α E_a/K_BT, activation energy of the compound was calculated. The frequency dependence of ac conductivity is explained on the basis of Correlated barrier Hopping Model. - Highlights: • The lattice parameters of CoTiO_3 were determined by using Rietveld refinement method. • The frequency dependence of ε_r was explained on the basis of Maxwell–Wagner model. • The depressed semicircles in Nyquist plot indicate the Non Debye-type response. • The frequency dependence of ac conductivity is explained on the basis of CBH Model.

[en] The dielectric properties of polycrystalline samples of SmAsO₄ and YAsO₄ are measured in the frequency range 10² to 10⁴ Hz and in the temperature region 295 to 473 K. The dielectric dispersion both, at room temperature and higher temerature is attributed to space charge polarisation. No dielectric anomaly is observed in the said temperature region. Moderately large value of the activation energy calculated from the conductivity versus temperature plots suggests that the conductivity may be associated with the ions. (author)

[en] Spectroscopic studies of some RNbO₄ compounds (R = La, Ce, Nd, Gd, and Y) prepared by high-temperature solid-state reactions have been carried out at room temperature. Infrared spectra, laser Raman spectra, and vibrational data of monoclinic rare earth orthoniobates are shown and discussed. The Raman lines for A_g modes are used for checking the influence of rare earth cations on inorganic oxoanions. The influence of lanthanide cations on NbO₄^3- anions was found to be remarkable

[en] The temperature and frequency dependence of dielectric properties for TlD₂PO₄ is investigated at atmospheric pressure. A dielectric anomaly is observed at 353 K. The thermal properties (DSC and DTA) of TlD₂PO₄ are studied from room temperature to 450 K. A thermal anomaly is observed at 353 K in DTA measurements, also. The dielectric hysteresis loop is studied at room temperature. The results show that TlD₂PO₄ is antiferroelectric in the room temperature phase. (author)

[en] The polycrystalline samples of Pb(Li_1/4Dy_1/4W_1/2)O₃ have been synthesized by high-temperature solid-state reaction techniques. Room temperature x-ray diffraction (XRD) studies of the compound provided preliminary structural data, and hence formation of a single phase desired material was confirmed. Detailed studies of dielectric constant(ε) and loss(tan δ) as a function of frequency (100 Hz to 10 kHz) at room temperature (298 K) and also as a function of temperature (liquid nitrogen to 403 K) at 10 kHz suggest that the compound undergoes a ferroelectric phase transition of diffuse type. (author). 17 refs., 5 figs., 1 tab