Small electron polarons bound to interstitial tantalum defects in lithium tantalate.

The absorption features of optically generated, short-lived small bound electron polarons are inspected in congruent lithium tantalate, LiTaO(LT), in order to address the question whether it is possible to localize electrons at interstitial TaV:VLidefect pairs by strong, short-range electron-phonon coupling. Solid-state photoabsorption spectroscopy under light exposure and density functional theory are used for an experimental and theoretical access to the spectral features of small bound polaron states and to calculate the binding energies of the small bound TaLi4+(antisite) and TaV4+:VLi(interstitial site) electron polarons. As a result, two energetically well separated (ΔE≈0.

Microwave Acoustic Attenuation in CTGS Single Crystals.

This article presents a study of special material properties of the single crystalline material CaTaGaSiO (CTGS = Catangasite). The comparatively highly ordered crystal structure and acceptable piezoelectric strength make it a candidate for microacoustic applications under extreme conditions. Obviously, low-loss dynamic behavior is typical for this crystal which consequently enables high-temperature use.

Linking the Electrical Conductivity and Non-Stoichiometry of Thin Film CeZrO by a Resonant Nanobalance Approach.

Bulk ceria-zirconia solid solutions (CeZrO, CZO) are highly suited for application as oxygen storage materials in automotive three-way catalytic converters (TWC) due to the high levels of achievable oxygen non-stoichiometry δ. In thin film CZO, the oxygen storage properties are expected to be further enhanced. The present study addresses this aspect.

Single crystals of ferroelectric lithium niobate-tantalate LiNbTaO solid solutions for high-temperature sensor and actuator applications.

Ferroelectric LiNbTaO solid solutions with various Nb/Ta ratio were grown from the melt by the Czochralski method. The exact composition of the grown crystals was determined by inductively coupled plasma atomic mass spectrometry. The dependence of the crystal composition on the composition of the initial melt was obtained and explained by a wide separation between the phase boundaries of the liquid and solid phases on the LiNbO-LiTaO phase diagram.

Determination of the Dielectric Properties of Storage Materials for Exhaust Gas Aftertreatment Using the Microwave Cavity Perturbation Method.

Recently, a laboratory setup for microwave-based characterization of powder samples at elevated temperatures and different gas atmospheres was presented. The setup is particularly interesting for investigations on typical materials for exhaust gas aftertreatment. By using the microwave cavity perturbation method, where the powder is placed inside a cavity resonator, the change of the resonant properties provides information about changes in the dielectric properties of the sample.

Full set of piezo-optic and elasto-optic coefficients of CaTaGaSiO crystals at room temperature.

The photoelasticity of the (CTGS) crystal was studied by an interferometric method based on a single-pass Mach-Zehnder interferometer. The maximum number of sample orientations for the piezo-optic experiments was applied to prove accuracy in the determination of the piezo-optic coefficients. Based on the matrices of the piezo-optic coefficients and the elastic stiffness coefficients, all the coefficients of the elastic-optic matrix are calculated.

Compressional-Wave Effects in the Operation of a Quartz Crystal Microbalance in Liquids:Dependence on Overtone Order.

The operation of the quartz crystal microbalance (QCM) in liquids is plagued by small flexural admixtures to the thickness-shear deformation. The resonator surface moves not only in the transverse direction, but also along the surface normal, thereby emitting compressional waves into the liquid. Using a simple analytical model and laser Doppler vibrometry, we show that the flexural admixtures are stronger on the fundamental mode than on the overtones.

Transport and Electromechanical Properties of CaTaGaSiO Piezoelectric Crystals at Extreme Temperatures.

Transport mechanisms in structurally ordered piezoelectric CaTaGaSiO (CTGS) single crystals are studied in the temperature range of 1000-1300 °C by application of the isotope O as a tracer and subsequent analysis of diffusion profiles of this isotope using secondary ion mass spectrometry (SIMS). Determined oxygen self-diffusion coefficients enable calculation of oxygen ion contribution to the total conductivity, which is shown to be small. Since very low contributions of the cations have to be expected, the total conductivity must be dominated by electron transport.

High-temperature electroacoustic characterization of Y-cut and singly-rotated Ca3TaGa3Si2O14 resonators.

Synthetic piezoelectric crystals in the P321 crystal class have been a focus of substantial research that is largely driven by applications in high-temperature resonant BAW and SAW sensing. Fully ordered crystals in this class, such as Ca3TaGa3Si2O14 (CTGS), have been suggested as offering the potential of electroacoustic performance that is superior to more extensively studied langasite (LGS) and langatate (LGT), which are partially disordered. In this study, the resonant frequencies, acoustic damping, and electrical conductivity of CTGS bulk acoustic resonators with Y-cut and (YXl)-30° crystal orientations and fundamental frequencies near 5 MHz are investigated at temperatures between ambient and 1100°C.

Defect chemistry, redox kinetics, and chemical diffusion of lithium deficient lithium niobate.

High-temperature optical in situ spectroscopy was used to investigate the defect absorption, redox kinetics, and chemical diffusion of a lithium deficient (48.4 mol% Li(2)O) congruent melting lithium niobate single crystal (c-LN). Under reducing atmospheres of various oxygen activities, a(O(2)), UV-Vis-NIR spectra measured at 1000 °C are dominated by an absorption band due to free small polarons centered at about 0.

Diffusion-related implications for langasite resonator operation.

Oxygen and gallium diffusivities in langasite were experimentally determined by analysis of diffusion profiles of 18O and 71Ga tracers by SIMS analysis as functions of temperature and doping. Strontium-enhanced diffusivities and activation energies of approximately 1.2+/-0.