Kazumasa Kushida

type:Article 大阪教育大学・教職実践演習ミニ講座「理科の実験・観察における安全」(2018年度)より,ICT教材を活用した授業実践について報告する。この講座では,理科の実験・観察を安全に行うために必要な知識を習得し,それを支える理論的根拠や経験知についてもディスカッションを通して深く理解することを目的としている。本稿にて報告する授業実践では,酸・塩基の中和実験(高校化学基礎)を撮影・編集した動画をICT教材として用い,実験時に事故を誘発し得る危険な兆候を察知する練習を行った。そして,そのような危険な兆候として,実験中の生徒の立ち位置・姿勢が悪いこと,実験卓上の整理整頓の不徹底等を見出した。 A course to learn how to safely conduct scientific experiments and observations is offered for prospective teachers (fourth grade students in Osaka Kyoiku University). This paper reports a practice in a class consisting of the course held in 2018. A video material is edited as an ICT teaching material, in which an experiment on neutralization of acids and bases is conducted in a first grade high school chemistry class. The practice in this report is aided by the ICT teaching material. The prospective teachers in the class are trained to find indications of danger in the laboratory through the video material.

We report the origin of low resistivity in ZnO bulk single crystals with thicknesses of 500 μm caused by gamma-ray irradiation. The crystals are irradiated at room temperature with gamma-rays of 1.17–1.33 MeV from a cobalt-60 source. The gamma-ray dose is 170 kGy. The resistivity at room temperature decreases from 4.1 × 10 Ω cm to 3.1 × 10 Ω cm by the irradiation. After the irradiation, slight increase in green luminescence at around 530 nm is observed, suggesting that zinc vacancy (V ), oxygen vacancy (V ) and oxygen interstitial (O ) are induced by Compton electrons emitted by the gamma-ray irradiation because this PL peak is a superposition consisting of the emissions relating to the V (∼490 nm), V (∼530 nm), and O (∼580 nm). The PL intensity of V is eight times larger than that of V The existence of V (g value is 1.996) is also observed by the electron paramagnetic resonance. This signal disappears by illuminating red LED with a wavelength of 654 nm, indicating V to V transition. The existence of V would suggest the formation of zinc interstitial (Zn ). In analogy with the low resistivity after Al-implanted ZnO, the origin of the low resistivity in gamma-ray irradiated ZnO is attributed to the Zn located at ∼30 meV below the conduction band. 4 2 + + 2+ Zn O i Zn O i O Zn. O O O Zn i i