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The dielectric spectra of aqueous solutions of ribonuclease A (RNase) have been measured in the frequency domain over the whole absorption region between 2 MHz and 72 GHz at 20°C in two solvents, pure water and 8 mol/1 urea solution. These environmental conditions promote the native and unfolded state of the protein, respectively. The results are discussed with regard to (i) the low and (ii) the high frequency part of the spectra. The contribution to (i) which is attributable to the tumbling motion of RNase is changed by the presence of urea, indicating that the RNase moieties are increased in polarity, but only insignificantly in size. From (ii) it is concluded that addition of urea leads to a change in the overall water structure and dynamics which is accompanied by an increased fraction of non‐associated solvent molecules. These are likely to be instrumental in the denaturation process.

The crystal structure and dielectric properties of LaYbO3 ceramics prepared by the mixed‐oxide route have been investigated. Rietveld refinements performed on X‐ray and neutron diffraction data show the room‐temperature structure to be best described by the orthorhombic Pnma space group [a=6.02628(9) Å, b=8.39857(11) Å, and c=5.82717(7) Å; Z=4, and theoretical density, Dx=8.1 g/cm3] in agreement with electron diffraction experiments. LaYbO3 ceramics fired at 1600°C for 4 h attain ∼97% of Dx and their microstructures consist of randomly distributed equiaxed grains with an average size of ∼8 μm. Conventional transmission electron microscopy shows densification to occur in the absence of a liquid phase and reveals domain‐free grains. The relative permittivity, ɛr, of LaYbO3 ceramics at radio frequencies is ∼26 in the range ∼10–300 K; however, a small dielectric anomaly is detected at ∼15 K. At room temperature and microwave frequencies, LaYbO3 ceramics exhibit ɛr∼26, Q×fr∼20 613 GHz (at 7 GHz), and τf∼−22 ppm/K. Q×fr show complex subambient behavior, decreasing from a plateau value of ∼20 000 GHz between ∼300 and 200 K to a second plateau value of ∼6000 GHz at ∼90 K before decreasing to <1000 GHz at ∼10 K. The large decrease in Q×fr at low temperature may be related to the onset of antiferromagnetism at ∼2.7 K.1

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