The influence of intense ultrasound applied during pressing on the optical and cathodoluminescent properties of conventionally sintered YSZ ceramics.

The aim of the present work was to investigate the effect of the ultrasonic treatment on the optical and cathodoluminescent properties of translucent ZrO2-8 mol.% Y2O3 (YSZ) ceramics obtained by conventional sintering of the pressed compacts. Treatment by intense ultrasound during dry pressing of the YSZ nanopowder leads to an increase in the relative density, a decrease in the pore size and an increase in the grain size of the sintered ceramics. It was shown that when the ultrasonic treatment is applied, the optical absorption cutoff wavelength of the sintered material is shifted to longer wavelengths, while the optical density of the material increases over the whole measurement spectrum. Samples subjected to ultrasonic treatment during pressing show higher intensity of luminescence than those obtained without the use of ultrasound, the shape of the luminescence spectra remaining unchanged. A correlation was obtained between the integral intensity of cathodoluminescence and the vacancy concentration in the sintered YSZ.

Speedup of doping fronts in organic semiconductors through plasma instability.

The dynamics of doping transformation fronts in organic semiconductor plasma is studied for application in light-emitting electrochemical cells. We show that new fundamental effects of the plasma dynamics can significantly improve the device performance. We obtain an electrodynamic instability, which distorts the doping fronts and increases the transformation rate considerably. We explain the physical mechanism of the instability, develop theory, provide experimental evidence, perform numerical simulations, and demonstrate how the instability strength may be amplified technologically. The electrodynamic plasma instability obtained also shows interesting similarity to the hydrodynamic Darrieus-Landau instability in combustion, laser ablation, and astrophysics.