E. P. Smirnova

Ferroelectric properties of SrTiO3-PbTiO3 solid solutions

Dielectric properties of ceramic samples of Sr1−xPbxTiO3 solid solutions for x varying from 0 to 0.3 have been studied. The ferroelectric phase transition in this system has been established to persist down to x=0.005. Within the x values of 0.002 to 0.05, the ferroelectric transition temperature is shown to follow the relation Tc=A(x−xc)1/2, with A=440 K and xc=0.002.

From incipient ferroelectricity in CaTiO3 to real ferroelectricity in Ca1−xPbxTiO3 solid solutions

Dielectric spectra of ceramic samples of Ca1−xPbxTiO3 (0⩽x⩽0.4) solid solutions were studied at frequencies between 10 Hz and 1 MHz in a temperature range of 4.2–300 K. A ferroelectric phase transition was observed at x=0.3 with transformation to a relaxor type behavior at x>0.3. The transition temperature Tc follows a linear dependence Tc∝(x−xc) with xc=0.28 contrary to a square-root dependence Tc∝(x−xc)1/2 predicted by the theory for incipient ferroelectrics. The critical concentration essentially exceeds the xc values for SrTiO3 and KTaO3 incipient ferroelectrics.

Elastic and piezoelectric properties of AlN and LiAlO 2 single crystals

We have successfully grown high-quality AlN piezoelectric single crystal using the sublimation technique. Transparent crack-free boules of approximately 15 mm in diameter and 25 mm in length along the [0001] direction were obtained, with coloring from amber to dark brown depending on growth temperature. Full sets of material parameters of grown AlN and commercially available LiAlO2 bulk crystals were measured at room temperature. Temperature coefficients of the material parameters of LiAlO2 were also obtained in a temperature range from -70 to +50°C.

Giant dielectric relaxation in SrTiO3-SrMg1/3Nb2/3O3 and SrTiO3-SrSc1/2Ta1/2O3 solid solutions

Ceramic samples of (1−x)SrTiO3-xSrMg1/3Nb2/3O3 and (1−x)SrTiO3-xSrSc1/2Ta1/2O3 were prepared, and their dielectric properties were studied at x=0.005–0.15 and 0.01–0.1, respectively, at frequencies 10 Hz–1 MHz and at temperatures 4.2–350 K. A giant dielectric relaxation was observed in the temperature range 150–300 K, and not so strong but well-developed relaxation was found in the temperature range 20–90 K. The activation energy U and the relaxation time τ0 were determined to be 0.21–0.3 eV and from 10−11 to 10−12 s for the high-temperature relaxation and 0.01–0.02 eV and 10−8–10−10 s for the low-temperature relaxation, respectively. The additional local charge compensation of the heterovalent impurities Mg2+ and Nb5+ (or Sc3+ and Ta5+) by free charge carriers or the host ion vacancies is suggested to be the underlying physical mechanism of the relaxation phenomena. On the basis of this mechanism, the Maxwell-Wagner model and the model of reorienting dipole centers Mg2+ (or Sc3+) associated with the oxygen vacancy are proposed to explain the high-temperature relaxation with some arguments in favor of the latter model. The polaron-like model with the Nb5+-Ti3+ center is suggested as the origin of the low-temperature relaxation. The reasons for the absence of ferroelectric phase transitions in the solid solutions under study are also discussed.

Dielectric relaxation in SrTiO3–SrMg1/3Nb2/3O3 and SrTiO3–SrSc1/2Ta1/2O3 solid solutions

Dielectric properties of ceramic samples of (1−x)SrTiO3–xSrMg1/3Nb2/3O3 and (1−x)SrTiO3–xSrSc1/2Ta1/2O3 solid solutions were studied at x⩽15% and x⩽10%, respectively. The real and imaginary parts of the dielectric constant were measured at frequencies between 10 Hz and 1 MHz and in a temperature range of 4.2–300 K. Remarkable relaxation was found between 80 and 300 K. The relaxation was suggested to be due to local charge compensation processes. The activation energy for these processes was determined to be (0.25±0.05) eV with τ0=(10−12…10−13) s.

Dielectric and electrostrictive properties of PMN-based complex perovskites

Abstract The effect of A-site and B-site modifications on lattice parameter, Curie temperture, diffuseness coefficient and dielectric permittivity of PMN-based solid solutions were studied. Electrostrictive constants and temperature dependencies of induced strain and electromechanical hysteresis were determined. These results make evident the importance of taking into account along with other parameters structural ordering of components developing new compositions.

Dielectric relaxation in SrTiO3: Mn

Dielectric relaxation (activation energy U≈0.03 eV, relaxation time τ0≈5×10−11 s) has been observed in SrTiO3: Mn solid solutions at low temperatures. It is assumed that the relaxation is related to reorientation of the polarons localized at defects of the {MnTi2+-O−} type and that the deviations from classical thermally activated behavior at the lowest temperatures reached are due to the quantum tunneling mode.

Pyroelectric and elastic properties of lead magnesium niobate-and barium titanate-based solid solutions near a phase transition

The pyroelectric, elastic, and electrostrictive properties of lead magnesium niobate-and barium titanate-based solid solutions were studied under a dc electric field near a phase transition. The results obtained for a relaxor transition (in a lead magnesium scandium niobate solid solution) are compared with those derived for a conventional ferroelectric transition (in a barium strontium titanate solid solution). The dielectric and electromechanical contributions to the induced pyroelectric effect are discussed.

PmC6. Giant electrostriction of ferroelectrics with diffuse phase transition - physics and applications

Abstract Giant Electrostriction (GE) of disordered ferroelectrics such as Ferroelectrics with Diffuse Phase Transition (FDPT) is noteworthy for application and basic researches. We present experimental data on the electrostrictive strain in FDPT. The description of the peculiarities of the electrostrictive strain is given. Some possible applications of the materials with GE are reviewed.

Pyroelectric effect in lead-magnoniobate-based solid solutions

A coordinated study of the dielectric, electrostriction, and pyroelectric properties of the lead-magnoniobate-based ceramic solid solutions 0.9PbMg1/3Nb2/3O3-0.1PbTiO3 and 0.55PbMg1/3Nb2/3O3-0.45PbSc1/2Nb1/2O3 conducted at the relaxor transition temperatures is reported. Electromechanical coupling stimulated by the giant electrostriction effect is shown to play an essential part in the pyroelectric effect.