Optical studies of terahertz phonons dynamics in small-grain polycrystalline cor

2019-06-10 21:26:50

The grain size dynamics phonons

责任者: Feofilov, S.P.;Kaplyanskii, A.A.;Kulinkin, A.B.;Zakharchenya, R.I. 单位: A.F. Ioffe Physical-Technical Inst, St. Petersburg, Russia 来源出处: Physica B: Condensed Matter,1999,263-264():695-697 摘要: The dynamics of terahertz acoustic phonons generated by optical pumping in ceramic-like α-Al2O3 with grain size to approximately 100 nm produced with the help of sol-gel technology was studied with the technique of optical detection of phonons by observation of probe Cr3+ and Mn4+ ions fluorescence. The dynamics of phonon distribution is very slow (approximately ms) and drastically differs from that in regular α-Al2O3 ceramics with micron grain size and is similar to that observed earlier in oxide glasses. The results are discussed in the framework of studies of phonons in different structured and spatially restricted Al2O3 materials with different ratios between phonon wavelength λ and crystallite size a. It is shown that the acoustic mismatch model which describes phonon scattering in regular ceramics is not valid for small-grain sol-gel produced ceramics-like material. 关键词: Corundum;Polycrystalline materials;Phonons;Grain size and shape;Nanostructured materials;Fluorescence;Scattering;Sol-gels;Mathematical models;Phonon scattering