Thermal and Optical Characterization of Undoped and Neodymium-Doped Y3ScAl4O12 Ceramics

Y3–3xNd3xSc1Al4O12 (x = 0, 0.01, and 0.02) ceramics were fabricated by sintering at high temperature under vacuum. Unit cell parameter refinement and chemical analysis have been performed. The morphological characterization shows micrograins with no visible defects. The thermal analysis of these ceramics is presented, by measuring the specific heat in the temperature range from 300 to 500 K. Their values at room temperature are in the range 0.81–0.90 J g1–K–1. The thermal conductivity has been determined by two methods: by the experimental measurement of the thermal diffusivity by the photopyroelectric method, and by spectroscopy, evaluating the thermal load. The thermal conductivities are in the range 9.7–6.5 W K–1 m–1 in the temperature interval from 300 to 500 K. The thermooptic coefficients were measured at 632 nm by the dark mode method using a prism coupler, and the obtained values are in the range 12.8–13.3 × 10–6 K–1. The nonlinear refractive index values at 795 nm have been evaluated to calibrate the nonlinear optical response of these materials.This work is supported by the Spanish Government under projects MAT2011-29255-C02-01-02, MAT2013-47395-C4-4-R, and the Catalan Government under project 2014SGR1358. It was also funded by the European Commission under the Seventh Framework Programme, project Cleanspace, FP7-SPACE-2010-1-GA No. 263044

Monoclinic morphotropic phase and grain size-induced polarization rotation in Pb(Mg1/3Nb2/3)O-3-PbTiO3

A detailed Rietveld analysis of x-ray data, collected at room temperature, was done on ceramics with controlled grain size between 100 nm and 4 mu m for (PbMg1/3Nb2/3O3)0.80-(PbTiO3)0.20 (PMN-PT20), i.e., a compound at the border of the so-called morphotropic phase boundary. With size reduction the polarization rotates within the monoclinic plane from M-B, i.e., P-x=P-y > P-z to M-A, i.e., P-x=P-y < P-z, and finally reaches a rhombohedral phase, i.e., P-x=P-y=P-z, below a critical value of similar to 200 nm without diminishing the amplitude of the polarization. This study provides an easy way to tailor the direction of polarization of these materials

Size-driven relaxation and polar states in PbMg1/3Nb2/303-based system

Nanocrystalline powders and ceramics with controlled grain size from 15 to 3000 nm of PbMg1∕3Nb2∕3O3(PMN) and (PMN)0.65−(PbTiO3)0.35(PMN−PT35) have been synthesized using the ball milling method. Dielectric experiments have revealed in PMN a disappearance of relaxation below ≈30nm grain size and combined x-ray and Raman experiments the vanishing of correlations between polar nanoregions (PNRs). A similar study in morphotropic compound PMN-PT35 has shown the appearance of a relaxor state below ≈200nm, associated to a destruction of the ferroelectric domains state towards PNRs in a paraelectric matrix. These phenomena are discussed in connection with pressure experiments from the literature and on the basis of polar states destabilization by both elastic and electric random fields changes associated with the size reduction

Size effects on the macroscopic properties of the relaxor ferroelectric Pb(Mg1/3Nb2/3)O3-PbTiO3 solid solution

International audience[No abstract available

Size effects in a relaxor : further insights into PMN

International audienc

Transition between the ferroelectric and relaxor states in 0.8Pb(Mg1/3Nb2/3)O-3-0.2PbTiO(3) ceramic

The phase transition between the ferroelectric and relaxor states for 0.8Pb(Mg1/3Nb2/3)O-3-0.2PbTiO(3) ceramics with high chemical homogeneity has been studied by measurements of the dielectric and elastic properties as a function of temperature and of thermal expansion. The room temperature ferroelectric phase structure has been studied in ceramics and powdered samples by Rietveld analysis of x-ray diffraction patterns and by ferroelectric hysteresis loops. Results indicate that the material has well defined, different transition and freezing temperatures, such as the transition is between a monoclinic Cm ferroelectric phase and the nonergodic glass state. The transition presents thermal hysteresis, not only in the transition temperature, but in the kinetics. This indicates that a quite sharp slowing down occurs in the temperature interval between 334 and 344 K: the transition temperatures on cooling and heating