Raman scattering study of ca-modified lead titanate

The paraelectric to ferroelectricphase transitionswere studied by Raman scattering in Ca-doped leadtitanate ceramics. The soft optic modes responsible for theferroelectricphase transitions were clearly observed. TheAi(lTO) mode, which softens toward Tc, contains four subpeaks.The frequencies of these subpeaks depend to a greatextent on the Ca content and the temperature. These behaviorsare discussed on the basis of the anharmonicity oflatticevibrations

Relation between Fractal Inhomogeneity and In/Nb-Arrangement in Pb(In1/2Nb1/2)O3

Relaxor ferroelectrics show substantial responses to electric fields. The key difference from normal ferroelectrics is a temperature-dependent inhomogeneous structure and its dynamics. The lead-based complex perovskite Pb(In1/2Nb1/2)O3 is an intriguing system in which the inhomogeneous structure can be controlled by thermal treatment. Herein, we report investigations of the phase transitions in single crystals of Pb(In1/2Nb1/2)O3 via changing the degree of randomness in which In and Nb occupy the B site of the ABO3 perovskite structure. We studied the dynamic properties of the structure using inelastic light scattering and the static properties using diffuse X-ray scattering. These properties depend on the degree of randomness with which the B site is occupied. When the distribution of occupied In/Nb sites is regular, the antiferroelectric phase is stabilised by a change in the collective transverse-acoustic wave, which suppresses long-range ferroelectric order and the growth of the inhomogeneous structure. However, when the B site is occupied randomly, a fractal structure grows as the temperature decreases below T*~475 K, and nanosized ferroelectric domains are produced by the percolation of self-similar and static polar nanoregions

Broadband inelastic light scattering of a relaxor ferroelectric 0.71Pb(Ni1/3Nb2/3)O3-0.29PbTiO3

Brillouin and Raman scatterings of a 0.71Pb(Ni1/3Nb2/3)O3-0.29PbTiO3 single crystal have been measured to investigate broadband inelastic spectra. The two different central peaks related to fast and slow relaxation processes have been observed separately. These two processes are attributed to the thermally activated switching of polarization in polar nanoregions. By the analysis of modified superparaelectric model, the activation energies of fast and slow relaxation processes are determined to be 3.66×103 and 4.31×102 K, respectively. The fast process with the lower activation energy probably originated from 180° switching, whereas the slow one with the higher energy from non-180° switching

The fate of caesium-137 in a soil environment controlled by immobilization on clay minerals

Caesium-137 (137Cs), with its high release rate and long half life, is the most important longterm contributor to environmental contamination of all the radionuclides released by the accident at the Fukushima Dai-ichi nuclear power plant in March 2011. There have been many surveys of the fate of 137Cs in terrestrial environments, especially after the atmospheric nuclear tests of the 1950s and 60s and the Chernobyl accident in 1986. Previous surveys revealed that most of the 137Cs deposited on land remains in the surface soil for decades and that 137Cs rarely exchanges with other cations (atoms that have lost an electron to become positively charged). The immobilization of 137Cs in soil is mostly ascribed to selective adsorption on clay minerals, particularly on illitic minerals. 137Cs is irreversibly retained at the fringe of the layered structure of illitic minerals, called the frayed-edge site, with much higher selectivity than other cations. Comparison of the radiocaesium interception potential (RIP) between soils and clay minerals indicates that the difference in the frayed-edge site capacity is largely dependent on the degree of weathering and the degree of hydroxy-Al interlayering in illitic minerals. Here we investigate the difference in the RIP values between mineral soils to predict the level of contamination of crops grown in 137Cs contaminated fields

STUDY ON ASSESSING THE VALUE OF THE TENGUIWA IRRIGATION CANAL

ABSTRACT: In Japan, following changes in socioeconomic conditions, such as financial deterioration, an increase in social capital, and a decrease in population, ideas about infrastructure improvement have greatly changed. Recently, irrigation canals possessing historic value have attracted the attention of the public as assets for community development. The present study focused on the Soja district, in which many historical and cultural resources exist but where these resources have not been developed. A questionnaire was administered to the local residents and revealed the value of the Tenguiwa Irrigation Canal as an environmental asset. The present study also examined the relationship between the value of the Tenguiwa Irrigation Canal as an environmental asset and the direction of community development in the Soja district

Large acoustic thermal hysteresis in relaxor ferroelectric Pb(Zn1/3Nb2/3)O3-PbTiO3

The diffuse phase transition in relaxor-based 0.93Pb(Zn1/3Nb2/3)O3–0.07PbTiO3 ferroelectric single crystals is studied by observing the large thermal hysteresis over 100 K of the longitudinal acoustic (LA) phonon. By observing this hysteresis in the LA phonon frequency with different temperature-cycles, it is concluded that nonequilibrium states are induced by supercooling. Relaxor ferroelectrics easily go supercooling, because they demonstrate structural hierarchy like glass-forming materials. The inhomogeneous structure disrupts sharp phase transitions, revealing diffuse phase transition on cooling. However, annealing at low temperatures reduces the inhomogeneity markedly. These interpretations are consistent with LA phonon behavior under electric fields, which reduce the inhomogeneity