Madoka Ono

Void structure in silica glass with different fictive temperatures observed with positron annihilation lifetime spectroscopy

We examine voids in silica glasses with different fictive temperatures using positron annihilation lifetime spectroscopy. The pick-off annihilation lifetime of ortho-positronium increases with the fictive temperature, Tf, indicating that the void size increases. High Tf leads to high density and low degree of network polymerization so that increasing void size means that the density fluctuation of the silica glass increases with high Tf. Assuming that such density fluctuation causes light scattering, the previously reported Tf dependence of the Rayleigh scattering coefficient can be well explained by the change in void size.

Gamma radiation resistance of spin Seebeck devices

Thermoelectric devices based on the spin Seebeck effect (SSE) were irradiated with gamma (γ) rays with the total dose of around 3 × 105 Gy in order to investigate the γ-radiation resistance of the devices. To demonstrate this, Pt/Ni0.2Zn0.3Fe2.5O4/Glass and Pt/Bi0.1Y2.9Fe5O12/Gd3Ga5O12 SSE devices were used. We confirmed that the thermoelectric, magnetic, and structural properties of the SSE devices are not affected by the γ-ray irradiation. This result demonstrates that SSE devices are applicable to thermoelectric generation even in high radiation environments.