Enhancement of the piezoelectric effect in Fe-substituted GaAsO4: A combined XRD, Raman spectroscopy and first principles study

Abstract

GaAsO4 is the highest performance piezoelectric material of the M III X V O4 alpha-quartz type group.First principles based calculations of the pure FeAsO4 show that the piezoelectric properties are strongly improved by replacing Ga 3+ by a chemical element of the d-bloc like Fe 3+ . 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 M III O4 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 analogs 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-

Anodic Reconstructed p+‐GaAs/a‐InAsN for Stable and Efficient Photoelectrochemical Hydrogen Evolution

“…According to the comparison of the Pourbaix diagram in the literature, [23][24][25] under the action of corresponding pH and applied bias voltage, the gallium atom will remain stable, while arsenic atom should be oxidized to GaAsO 4 , the highest value arsenate of pentavalent. However, we do not detect any characteristic vibration peaks belonging to AsO 4 3− groups (894, 861, 837, 826, 460, 433, 394, 346, 327 cm −1 ) [26] in the Raman spectra of the samples, suggesting that no hypervalent arsenate is produced on the sample. Hence, after the catalytic oxidation of active indium clusters to In 3+ on the surface of GaAs (200), the arsenic atoms in GaAs are anchored to form In─As chemical bond to avoid arsenide oxidation.…”

Composites, Fabrication and Application of Polyvinylidene Fluoride for Flexible Electromechanical Devices: A Review

“…The polarization process is usually performed by applying a high electric field. PZT-series materials such as PMN-PZT The piezoelectric effect [27,28] refers to the polarization of certain dielectrics in a specific direction under the action of an external force. A dielectric material has positive and negative charges on two opposite surfaces.…”