熱測定
Online ISSN : 1884-1899
Print ISSN : 0386-2615
ISSN-L : 0386-2615
39 巻, 3 号
選択された号の論文の5件中1~5を表示しています
解説
  • 松岡 純
    2012 年 39 巻 3 号 p. 106-111
    発行日: 2012/07/25
    公開日: 2022/11/20
    ジャーナル フリー
    After introducing the basic approach to thermal conductivity of glass, composition dependence of the thermal conductivity of oxide and chalcogenide glasses are reviewed. In simple silicate glasses, increase of the non-bridging oxygen is found to decrease the phonon mean free path and also the thermal conductivity. Substitution of silicon to aluminum in silicate glass is found to increase the thermal conductivity, which should be due to the increase of connectivity of glass network or decrease of non-bridging oxygen. In borate glasses, increase of the four-fold coordinated boron is found to increase the thermal conductivity and borate anomaly or the maximum against alkali content is found in alkali borate glasses. In borosilicate glasses, thermal conductivity is not so high compared with aluminosilicate glasses. This should be due to the difference of the vibration frequency of Si-O and B-O bonds which would cause the termination of the propagation of lattice vibration. In chalcogenide glasses, maximum of the thermal diffusivity is shown when average coordination number is 2.6.
  • 八島 正知
    2012 年 39 巻 3 号 p. 112-115
    発行日: 2012/07/25
    公開日: 2022/11/20
    ジャーナル フリー
    Ferroelectric ceramic materials with large spontaneous polarization and high dielectric and piezoelectric responses are attractive due to a wide range of applications. Here I describe the crystal structure analysis of ferroelectric silver niobate AgNbO3 and 0.4 PbTiO3-0.6 BiFeO3. The space group of ferroelectric AgNbO3 was found to be non-centrosymmetric Pmc21. Through the neutron and synchrotron powder diffraction analyses, and first-principles Density Functional Theory (DFT) calculations we have determined the atomic positions in the unit cell of AgNbO3. The net spontaneous polarization in AgNbO3 is essentially ascribed to the atomic displacements along the c axis in Pmc21. The ferroelectric-antiferroelectric transition of AgNbO3 is suggested to be a Pmc21-Pbcm transformation. In ferroelectric tetragonal 0.4 PbTiO3-0.6 BiFeO3, we have demonstrated the experimental and theoretical evidences for the hybridization between (Bi,Pb)(6s,6p) and O(2p) orbitals, which is the key for the extremely large tetragonality (axial ratio c/a), high Curie temperature TC and ferroelectricity of 0.4 PbTiO3-0.6 BiFeO3.
  • 小林 広和
    2012 年 39 巻 3 号 p. 94-98
    発行日: 2012/07/25
    公開日: 2022/11/20
    ジャーナル フリー
    The current topics of inclusion compounds (ICs) synthesized using organic 1-D porous materials and organic radicals, as well as on the TG-DTA measurements of ICs are reviewed. In these ICs, organic 1-D porous materials, such as tris(o-phenylenedioxy)cyclotriphophazene (TPP) and 2,4,6-tris-4-(chlorophenoxy)-1,3,5-triazine (CLPOT), are used as templates to align stable organic radicals in a 1-D manner based on host-guest interactions. Several TG-DTA measurements of [(organic 1-D porous materials)/(organic radicals)] ICs, such as [(TPP)2/(DTBN)1.25] and [(CLPOT)2/TEMPO] ICs, have been explained in detail (DTBN = di-t-butyl nitroxide radical, and TEMPO = 2,2,6,6-tetramethyl-1-piperidinyl-1-oxyl radical). From the results of TG measurements, the inclusion of organic radicals in TPP or CLPOT nanochannels and the amount of guest radicals are confirmed. These results are available to design and construct a new “organic” magnet.
  • 隅山 兼治
    2012 年 39 巻 3 号 p. 99-105
    発行日: 2012/07/25
    公開日: 2022/11/20
    ジャーナル フリー
    This article briefly describes a history of the development of Fe-Ni Invar alloys whose temperature dependence of thermal expansion and elastic constants are extremely small: they have been used for a international metric standard and several precision instruments. It also describes a brief concept of low temperature thermometers whose electrical resistance are markedly dependent on temperature but independent on magnetic field: they can be used in a superconducting magnet. These characteristics are based on competing effects: anharmonic lattice vibration and magnetostriction in the former, while electron scattering and electron localization by low dimensionalities and random distribution of lattice impurities in the latter. The two examples presumably give researchers and engineers in the fields of calorimetric and thermal analyses some hints and guiding principles for developing environment-adaptable materials and sensors.
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