Tohoku University · Materials Science
Professor Takuya Hasegawa's research lab specializes in advanced functional materials, with a primary focus on luminescent phosphors for solid-state lighting and energy-efficient lighting technologies. The lab investigates novel garnet-structured and rare-earth-doped phosphors, emphasizing high quantum efficiency, tunable emission colors, and precise control of activator ion valence states. Additionally, the lab contributes to energy-saving technologies through research on high-efficiency combustion systems and thermal processes for industrial applications. Their work also extends to environmental science, analyzing ocean heat content anomalies and their links to climate phenomena such as ENSO.
Figures are computed from collected data and may differ slightly.
Large-extent LGE correlates with absence of LV functional improvement and high incidence of adverse outcomes in patients with CS after steroid therapy.
Extensive attention has been focused toward studies on inexpensive and rare-earth-free garnet-structure vanadate phosphors, which do not have a low optical absorption due to the luminescence color being easily controlled by its high composition flexibility. However, bluish emission phosphors with a high quantum efficiency have not been found until now. In this study, we successfully discovered bluish-white emitting, garnet structure-based LiCa<sub>3</sub>MV<sub>3</sub>O<sub>12</sub> (M = Zn and
Results are presented on the thermal and chemical characteristics of flames using high-temperature combustion air and liquified petroleum gas (LPG) as the fuel. The stability limits of these flames are extremely wide as compared to any other method of flame stabilization. This study is part of the Japan national project directed to develop advanced industrial furnace designs that provide approximately 30% energy savings and hence CO 2 reduction, 30% reduction in the furnace size, and 25% reducti
A novel red emitting, Ce<sup>3+</sup>-activated Sr<sub>3</sub>Sc<sub>4</sub>O<sub>9</sub> phosphor were discovered, and its luminescent properties were investigated.
Anomaly fields of upper-ocean heat content (OHC) in the Pacific basin from 30°S to 60°N over a 45-yr period are analyzed with special reference to their relationship with El Niño–Southern Oscillation (ENSO) events. In the present study, for convenience, the OHC is defined as vertically averaged temperature from the sea surface to 300-m depth. Based on a cluster analysis, it is found that interannual variability with a period of 3–6 yr is dominant in the eastern and western tropical Pacific, whil
Obtaining highly efficient photoluminescence with Mn<sup>4+</sup>-activated phosphors, which have been extensively studied in diverse lighting devices, requires the precise control of the manganese valence states. However, this control is difficult to achieve because manganese ions can have various valence states ranging from divalent to heptavalent. Additionally, the concentrations of Mn ions in each valence state, especially the effective Mn<sup>4+</sup> concentration, have never been quantita
The development of integrated, coal-gasification combined cycle (IGCC) systems provides cost-effective and environmentally sound options for meeting future coal-utilizing power generation needs in the world. The Japanese government and the Electric Power Industries in Japan promoted research and development of an IGCC system. We have being working on developing a low-NOx combustion technology used in gas turbine combustors for IGCC. Each gaseous fuel produced from some raw materials contained CO
Raman scattering spectra of iridium pyrochlore oxides R2Ir2O7 (R=Nd, Sm, and Eu) have been measured. These three compounds undergo metal-insulator transition. Below the transition temperature TMI, new peaks appear for R = Sm and Eu, but no remarkable change for R = Nd. Therefore, Sm2Ir2O7 and Eu2Ir2O7 accompany structural change with the transition, but not the case for Nd. Even if Nd2Ir2O7 deforms, the distortion is different from that of Sm2Ir2O7 and Eu2Ir2O7, because the spectra of Nd are cle
Decadal‐scale variability of upper ocean heat content (OHC) in the tropical Pacific is investigated and is compared with that of ENSO scale. The decadal‐scale OHC anomaly with a period of about 13 years shows anticlockwise propagations in the tropical North Pacific like as that of ENSO scale. It is also shown that the entire equatorial OHC anomaly leads Niño‐3 index anomaly by about a quarter (about 3 years) of the period of the decadal variability in the tropical Pacific. This time lag of a qua
We employed an oxygen-pressure method as a novel approach to improve the emission intensity of a Ca14Zn6Al10O35:Mn4+ phosphor. With this new approach, the Ca14Zn6Al10O35:Mn4+ phosphor exhibited near-infrared emission under excitation at 450 nm, and the emission intensity of a Ca14Zn6(Al0.97Mn0.03)10O35 phosphor was effectively enhanced by approximately 143% compared with that of a Ca14Zn6(Al0.97Mn0.03)10O35 phosphor synthesized by a conventional solid-state reaction method in air.
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