High temperature piezoelectric properties of flux-grown α-GeO2 single crystal

Abstract

The temperature-dependence of the piezoelectric properties of trigonal -GeO2 single-crystals obtained by the high-temperature flux method was measured by the resonance technique of the electrical impedance in the 20°C -600°C range. To approach the values of the two independent piezoelectric coefficients d11 and d14, we first measured as a function of temperature the elastic coefficients S11, S14 and S66 and the dielectric permittivity 11 which are involved in the coupling coefficient k of both the thickness shear mode and the transverse mode. A Y-cut plate with a simple +45°-rotation ((YXtwl) +45°/0°/0°) was used to measure the coupling coefficient of the thickness shear mode, and two X-turned plates ((XYtwl) +45°/0°/0° and (XYtwl) -45°/0°/0°) were prepared to characterize the coupling coefficient of two transverse modes. From the whole experimental measurements, the piezoelectric coefficients of -GeO2 were calculated up to 600 °C. They show that this crystal is one of the most efficient in regard of the -quartz-like family at room temperature, and that its thermal comportment retains large piezoelectric properties up to 600°C.

Impact of Crystal Density on the Electrochemical Behavior of Lithium-Ion Anode Materials: Exemplary Investigation of (Fe-Doped) GeO2

“…This finding has, in fact, potential implications also beyond battery research, as quartz-like GeO 2 is piezoelectric, and the phase stabilization therefore allows the potential application of such material in a substantially extended temperature range. 46 Eventually, we performed a comparative electrochemical characterization of these two samples, i.e., GeO 2 @700°C and Ge 0.9 Fe 0.1 O 2 @900°C, to study the effect of the Fe doping on the de-/lithiation behavior (Figure 7). The cyclic voltammograms of both samples (Figure 7a) show essentially the same features, i.e., three current peaks during the initial lithiation at around 1.0, 0.4, and 0.1/0.05 V, which can be ascribed to the SEI formation and potentially an initial lithiation forming Li x GeO 2 , 22 the conversion reaction, and the alloying reaction, respectively.…”

Thin films of the $$\alpha$$-quartz $$Si_xGe_{1-x}O_2$$ solid solution

“…The quartz family includes compounds with formulae (T = Si, Ge) and (M = B, Al, Ga, Fe, Mn and X = P, As). Among them, and have the most distorted structure, with displaying a 11 , 12 compared with the 2.31 pC / N of 13 . Theoretical calculations of a quartz-type SAW device estimate an electromechanical coupling coefficient that can reach a maximum value of 0.34% 14 , compared to the 0.16% of the well-known ST-cut crystals 15 .…”

The open-framework structure of KSbGe3O9 flux-grown crystals investigated by X-ray diffraction, vibrational spectroscopy, and DFT calculations

“…In this context, the searching and the development of transparent and colorless germanate single-crystals with a non-centrosymmetric structure and enhanced properties are important. For industrial applications in harsh environment (with T > 600°C), lead-free materials that can operate under extreme stress without degradation should have a stoichiometric chemical composition and structural stability in a large thermal domain as encountered for the non-polar uniaxial -GeO2 single crystal [6,7].…”