Abstract GaAsO4 is the highest performance piezoelectric material of the MIIIXVO4 alpha-quartz type group. First principles based calculations of the pure FeAsO4 show that the piezoelectric properties are strongly improved by replacing Ga3+ by a chemical element of the d-bloc like Fe3+. For GaAsO4, our calculations give, d11 = 7.08 and d14 = 5.76 pC/N, while these values are significantly higher in FeAsO4 to reach d11 = 18.77 and d14 = 13.78 pC/N; about a factor of three greater than in GaAsO4 due to the increase of the elastic compliances of FeAsO4 with respect to GaAsO4. These results show that the electronic configuration and particularly the involvement of the d-orbitals in the M-O bonds in the MIIIO4 tetrahedron could be at the origin of this increasing. By considering a linear dependence of d11 or d14 between the parent compounds, GaAsO4 and FeAsO4, we get the following equations for the Ga(1-x)FexAsO4 solid solution: d11 [pC/N] = 11.689 xFe + 7.082 and d14 [pC/N] = 8.021 xFe + 5.762. These predictions motivated the first synthesis of mixed Ga(1-x)FexAsO4 solid solutions with x = 0,09; 0,18 and 0,45. The hydrated compounds, Ga1-xFexAsO4,2H2O, were obtained by hydrothermal synthesis and the alpha-quartz phases Ga1-xFexAsO4 were crystallized with a thermal treatment in an oven at 600 °C for 24h. XRD patterns show that the cell parameters are in accordance with a Vegard's law for the orthorhombic hydrated phases (Pbca space group) and for the trigonal dehydrated alpha-quartz phases (P3121 space group). Raman spectroscopy data obtained for the hydrated phases confirm the results of the literature on FeAsO4·2H2O, GaAsO4·2H2O and other arsenate analogues as well as their substituted analogues on the M and X sites. For the dehydrated alpha-quartz phases, all the main peaks observed in Raman spectra have been observed and the assigned by analyzing the experimental spectra measured in solid solutions and the calculated spectra in the parent end-member compounds. DFT calculations were used to identify the Raman vibrational modes. As in the case of GaAsO4, no libration mode of oxygen atoms is present for FeAsO4 that could lead to a very high thermal stability. These results prove the interest of α-quartz type FexGa1-xAsO4 solid solutions.

中文翻译：

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Fe 取代 GaAsO4 压电效应的增强：结合 XRD、拉曼光谱和第一性原理研究

摘要 GaAsO4 是 MIIIXVO4 α-石英型族中性能最高的压电材料。基于第一性原理的纯 FeAsO4 计算表明，通过将 Ga3+ 替换为 d-bloc 的化学元素（如 Fe3+），压电性能得到显着改善。对于 GaAsO4，我们的计算得出，d11 = 7.08 和 d14 = 5.76 pC/N，而 FeAsO4 中的这些值明显更高，达到 d11 = 18.77 和 d14 = 13.78 pC/N；由于 FeAsO4 相对于 GaAsO4 的弹性柔量增加，大约比 GaAsO4 大三倍。这些结果表明，电子构型，特别是 MIIIO4 四面体中 MO 键中 d 轨道的参与可能是这种增加的起源。通过考虑母体化合物之间 d11 或 d14 的线性相关性，GaAsO4 和 FeAsO4，我们得到以下 Ga(1-x)FexAsO4 固溶体方程：d11 [pC/N] = 11.689 xFe + 7.082 和 d14 [pC/N] = 8.021 xFe + 5.762。这些预测促成了 x = 0,09 的混合 Ga(1-x)FexAsO4 固溶体的首次合成；0,18 和 0,45。水合化合物Ga1-xFexAsO4,2H2O是通过水热合成获得的，α-石英相Ga1-xFexAsO4在600℃的烘箱中热处理24小时结晶。XRD 图案表明，对于正交水合相（Pbca 空间群）和三角脱水 α-石英相（P3121 空间群），电池参数符合 Vegard 定律。为水合相获得的拉曼光谱数据证实了有关 FeAsO4·2H2O 的文献结果，GaAsO4·2H2O 和其他砷酸盐类似物以及它们在 M 和 X 位点上的取代类似物。对于脱水的 α-石英相，通过分析在固溶体中测量的实验光谱和母体端元化合物中的计算光谱，已经观察到了在拉曼光谱中观察到的所有主峰，并进行了分配。DFT 计算用于识别拉曼振动模式。与 GaAsO4 的情况一样，FeAsO4 不存在氧原子的释放模式，这可能导致非常高的热稳定性。这些结果证明了 α-石英型 FexGa1-xAsO4 固溶体的重要性。通过分析在固溶体中测量的实验光谱和母体端元化合物中的计算光谱，已经观察到并分配了在拉曼光谱中观察到的所有主峰。DFT 计算用于识别拉曼振动模式。与 GaAsO4 的情况一样，FeAsO4 不存在氧原子的释放模式，这可能导致非常高的热稳定性。这些结果证明了 α-石英型 FexGa1-xAsO4 固溶体的重要性。通过分析在固溶体中测量的实验光谱和母体端元化合物中的计算光谱，已经观察到了在拉曼光谱中观察到的所有主峰并进行了分配。DFT 计算用于识别拉曼振动模式。与 GaAsO4 的情况一样，FeAsO4 不存在氧原子的释放模式，这可能导致非常高的热稳定性。这些结果证明了 α-石英型 FexGa1-xAsO4 固溶体的重要性。