Effect of incorporation of iron and aluminum on the thermoelastic properties of magnesium silicate perovskite
Effect of incorporation of iron and aluminum on the thermoelastic properties of magnesium silicate perovskite
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DOI：
10.1007/s00269-006-0134-6
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发表时间：
2007-04-01
影响因子：
1.4
通讯作者：
Kikegawa, Takumi
中科院分区：
文献类型：
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作者：
Nishiyama, Norimasa;Yagi, Takehiko;Kikegawa, Takumi
对由天然斜方辉石合成的含铁和铝的富镁硅钙钛矿（FeAl - Pv）进行了原位X射线衍射测量。测量是在19 - 32吉帕的压力和300 - 1500开尔文的温度下，使用带有八个烧结金刚石压砧的川井型装置和同步辐射进行的。使用带有两个样品室的高压腔进行了两次实验，在同一个腔中同时合成了镁硅钙钛矿（Mg - Pv）和FeAl - Pv。因此，我们能够在相同的压力 - 温度条件下测量Mg - Pv和FeAl - Pv的比容（V/V₀）。在所有测量条件下，FeAl - Pv的比容值与Mg - Pv的比容值在2倍标准偏差范围内一致，这有力地表明在这种成分、压力和温度范围内，铁和铝的掺入对硅酸镁钙钛矿的热弹性性质的影响无法检测到。使用具有一个样品室的高压腔又进行了两次实验，并分别在高达32吉帕的压力和1500开尔文的温度下测量了FeAl - Pv的晶胞体积。将FeAl - Pv钙钛矿的所有晶胞体积数据拟合到高温的Birch - Murnaghan状态方程，并在假设K'(300,0) = 4的情况下确定了这种钙钛矿的一整套热弹性参数。所确定的参数为：K₃₀₀,K₀ = 243(±3)吉帕，(∂Kₜ,K₀/∂T)(P) = - 0.030(±8)吉帕/开尔文，a(0) = 2.78(±18)×10⁻⁵ 开⁻¹，b(0) = 0.88(±28)×10⁻⁸ 开⁻²，其中a₀和b₀是描述零压热膨胀的以下表达式的系数：α(T,0) = a(0) + b(0)T。FeAl - Pv的状态方程参数与在下地幔最上部对应的条件下的镁硅钙钛矿的参数非常吻合。
In situ X-ray diffraction measurements of Fe- and Al-bearing MgSiO3-rich perovskite (FeAl-Pv), which was synthesized from a natural orthopyroxene, were performed at pressures of 19 - 32 GPa and temperatures of 300 - 1,500 K using a combination of a Kawai-type apparatus with eight sintered-diamond anvils and synchrotron radiation. Two runs were performed using a high-pressure cell with two sample chambers, and both MgSiO3 perovskite (Mg-Pv) and FeAl-Pv were synthesized simultaneously in the same cell. Thus we were able to measure specific volumes (V/V-0) of Mg-Pv and FeAl-Pv at the same P - T conditions. At all the measurement conditions, values of the specific volume of FeAl-Pv are consistent with those of Mg-Pv within 2 Standard Deviation, strongly suggesting that effect of incorporation of iron and aluminum on the thermoelastic properties of magnesium silicate perovskite is undetectable in this composition, pressure, and temperature range. Two additional runs were performed using a high-pressure cell that has one sample chamber and unit-cell volumes of FeAl-Pv were measured at pressures and temperatures up to 32 GPa and 1,500 K, respectively. All the unit-cell volume data of FeAl-Pv perovskite were fitted to the high temperature Birch - Murnaghan equation of state and a complete set of thermoelastic parameters of this perovskite was determined with an assumption of K'(300,0) = 4. The determined parameters are K-300,K-0 = 243( 3) GPa, (partial derivative K-T,K- 0/partial derivative T)(P) = - 0.030( 8) GPa/ K, a(0) = 2.78( 18) x 10(-5) K-1, and b(0) = 0.88( 28) x 10(-8) K-2, where a0 and b0 are the coefficients of the following expression describing the zero-pressure thermal expansion: alpha(T,0) = a(0) + b(0)T. The equation-of-state parameters of FeAl-Pv are in good agreement with those of MgSiO3 perovskite at the conditions corresponding to the uppermost part of the lower mantle.