The incommensurate modulation in a synthetic iron-bearing åkermanite, Ca₂(Mg, Fe)Si₂O₇, has been determined at room temperature by the five-dimensional refinements of the structure. The basic structure is tetragonal P-42₁m with unit-cell dimensions a=7.8679(3), c=5.0144(2)Å, V=310.41(2)ų, Z=2, M=286.69, D_x=3.067Mg·m⁻³, MoKα with graphite monochromator, μ=3.199mm⁻¹, F(000)=284.49, Mg/(Mg+Fe)=0.554(6), R=0.065 for 770 unique reflections. The modulated structure is also tetragonal P_P4mg^p-42_1m, k₁=0.295(2)×(a^*+b^*), k₂=0.295(2)×(-a^*+b^*), where k₁, k₂ are the wave vectors and a^*, b^* the reciprocal lattice vectors of the basic structure. R=0.136 for 3965 unique reflections. The modulation is caused mainly by the shifts of Ca and O atoms, and substitutional modulation at (Mg, Fe) sites was not detected in the present studies. Six-coordinated Ca forming a distorted oxygen octahedra exists in the modulated structure and most of them form clusters together with the flattened (Mg,Fe)O₄ tetrahedra. The number of the clusters in the present material is less than that in Co-åkermanite. The reason may be attributed to the disorder of the modulation amplitudes and wavelength.

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Condensation experiments have been carried out with a new condensation furnace in H₂ at low pressures (1.4, 1.4×10⁻¹, and 1.4×10⁻² Pa) using an evaporation source of forsterite powder heated at about 1500°C. Large amounts of condensates (up to a few hundreds of mg) were recovered as a function of temperature (from about 1350°C to room temperature) at 1.4 Pa, where the evaporated molecules from forsterite sufficiently collided with H₂ molecules. Forsterite, forsterite + silicon, forsterite + silicon + enstatite and amorphous material condensed with decreasing temperature under a reducing condition in a Ta crucible, while forsterite, forsterite + clinoenstatite and amorphous materials condensed near a neutral redox condition in a Mo crucible. These condensation sequences are essentially the same as fractional condensation sequences expected from the phase diagrams in the system Mg–Si–O–H constructed by thermodynamic calculations. Kinetic effects are also superimposed on the fractional condensation. For example, dendritic crystals of forsterite and clinoenstatite, and amorphous materials condensed due to nucleation delay of the silicates. Each whisker of the den-drites was formed by the vapor-liquid-solid growth mechanism with metastable nucleation of melt droplets. The elongation of clinoenstatite whiskers (c-axis) is different from that in interplanetary dust particles (a-axis). Euhedral forsterite crystals (a few μm in size and elongated to the c-axis), which condensed at high temperatures (>1000°C), have similar size and morphologies of olivine in matrix of chondrites. Condensation of clinoenstatite at high temperature (about 900°C) may indicate easy pyroxene condensation in the primordial solar nebula.

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Cu₃BiS₃ has been synthesized to clarify the thermal nature related to the ionic conduction. Heating and cooling measurements by the DSC showed reversible nature as a whole, except for a little hysteresis on temperature of the first order transition around 100–110°C. Resistivity decreased steeply from room temperature to about 77–90°C, above which the material showed good ionic conductivity. In cooling process, however, the resistivity did not recover the original value until room temperature. Several days are necessary to get back the initial resistivity at room temperature. The irreversible nature on conductivity will be explained by the existence, at least partially, of the metastable and electrolytic state on cooling to the room temperature. The reversible profiles in DSC and TMDSC indicates that the first order transition has essentially little or no effect to the conversion to the solid electrolyte. Temperature modulated DSC data were correlated well to heat capacity profiles obtained so far from the adiabatic calorimety and DSC-data.

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