High temperature piezoelectric properties of flux-grown α-GeO 2 single crystal

International audienceThe 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

Order-disorder evolution in solid solutions of the NLO material KTiOPO

K0.88Rb0.12TiOPO4 and K0.465Rb0.535TiOPO4 solid solutions of the potassium titanyl phosphate (KTiOPO4, space group Pna21) family, are described at 293, 473, 673, 873 and at 973 K. Their high resolution structures are obtained by using accurate single-crystal X-ray diffraction techniques at high resolution, (sin $\theta / \lambda)_{\rm max} = 1.36$ Å-1. Large anharmonic motion of alkaline ions increasing with temperature allows the evolution of the rubidium and potassium ions repartition in the two alkaline sites versus temperature. To describe this motion inducing ionic conductivity phenomenon and to determine accurately the order-disorder evolution, two alkaline site refinement models are developed and discussed. A thermodynamic model, which uses a barrier-potential model, is also developed to specify the different interactions operating in the order-disorder evolution, and more generally interactions between alkaline ions and the framework

Experimental demonstration of Surface Acoustic Wave propagation on α-GeO2 for wireless, passive sensor design

International audienceOn the path towards developing passive transducers for wireless sensing in high temperature >560◦C) environments.We experimentally demonstrate the design, manufacturing and interrogation of resonators patterned on GeO2 substrates

Experimental demonstration of Surface Acoustic Wave propagation on α-GeO2 for wireless, passive sensor design

International audienceOn the path towards developing passive transducers for wireless sensing in high temperature >560◦C) environments.We experimentally demonstrate the design, manufacturing and interrogation of resonators patterned on GeO2 substrates

Anharmonicity and Effect of the Nanostructuring on the Lattice Dynamics of CrSi 2

International audienc

Optical characterization of YCa4 O(BO3 )3 and Nd :YCa4 O(BO3 )3

International audienceWe report a complete optical characterization of YCa4O(BO3)3 and Nd:YCa4O(BO3)3 crystals. We studied the relative orientation between the dielectric and the crystallographic frames as a function of the wavelength and performed accurate phase-matching angles measurements for second harmonic generation, using a single crystal cut as a sphere. We also recorded polarized luminescence spectra of Nd:YCOB along the principal axes of the dielectric frame. For both crystals, we measured the gray-tracking and the thermo-optic properties as a function of temperature and wavelength using oriented slabs. Finally, we measured all their dielectric and electro-optic coefficients, as a function of frequency and wavelength

Optical characterization of YCa4O(BO3)3 and Nd:YCa4O(BO3)3 crystals

We report a complete optical characterization of YCa4O(BO3)3 and Nd:YCa4O(BO3)3 crystals. We studied the relative orientation between the dielectric and the crystallographic frames as a function of the wavelength and performed accurate phase-matching angles measurements for second harmonic generation, using a single crystal cut as a sphere. We also recorded polarized luminescence spectra of Nd:YCOB along the principal axes of the dielectric frame. For both crystals, we measured the gray-tracking and the thermo-optic properties as a function of temperature and wavelength using oriented slabs. Finally, we measured all their dielectric and electro-optic coefficients, as a function of frequency and wavelength