Papers by Author: Saroj Rujirawat

Abstract: In this study, a room temperature aging behavior of Ba(Ti0.99Fe0.01)O3 was investigated. It was found that the dielectric constant decreased with time and ferroelectric P-E hysteresis loops became constricted loops after aging. Moreover, the room temperature aging behavior under various stresses was also observed. It was found that the relative changes of dielectric constant with time of Ba(Ti0.99Fe0.01)O3 ceramics under stress were lower than those under the stress-free condition. For P-E hysteresis loop measurement, it can be observed that P-E hysteresis loop of Ba(Ti0.99Fe0.01)O3 ceramics became constricted loops and remanant polarizations (Pr), saturated polarizations (Ps) were decreased after aging under all stress levels. These results suggested that the applied stress may partly clamp the domain wall motion, and altered the aging behavior of the ceramics.

Abstract: In this work, an experimental X-ray Absorption Spectroscopy (XAS) measurement was employed to determine the local structure of Mn in BaTiO3. Synchrotron X-ray absorption near-edge structure (XANES) experiments were performed on Mn-doped BaTiO3 samples. The BaTi0.8Mn0.2O3 powders were used for the XAS experiment. XAS spectra at the Mn K-edge were recorded in transmission mode. The spectra were collected at ambient temperature with a Ge(111) double crystal monochromator and recorded after performing an energy calibration. The features of the measured Mn K-edge XANES were consistent with Mn on the Ti site and inconsistent with Mn on other sites. The clear agreement was the strongest evidence of Mn substituting for Ti in BaTiO3.

Abstract: In this note, we describe the upgrade effort to convert the SIAM Photon source into an Xray synchrotron radiation facility with photon energies up to some 15 keV. This conversion of SIAM Photon into a third generation light source can be achieved through an increase of the electron beam energy and the addition of recently available superconducting wavelength shifter and multipole wiggler magnets. A gradual retrofit of vacuum chambers aiming at a reduction of electron beam instabilities as well as a modification of the focusing structure are expected to greatly increase the brightness of the photon beam. These upgrades will be implemented gradually over a few years to minimize the interruption of ongoing experimental activities. As an ultimate upgrade, a study has been started which shows the feasibility to implement a 2 GeV storage ring replacing the present ring in the same foot print. This new ring is configured to provide double the number of insertion device photon beam lines.