Doping ceramics

FIGURE1.9 The grain boundary and bulk conductivities at 300°C for 8YSZ ceramics doped with ZnO with reference to the undoped YSZ sintered at the same temperature as a function of ZnO content [52]. 

S. L. Wu, H. P. Li et al.. Sol-gel preparation and characteristic on ultrafme BaTiOj and Semiconducting BaTiOj Ceramics doped with yttrium, Functional Material, 26(1995) pp. 427-430. 

The importance of transparent glass-ceramics doped by Cr as potential new materials for luminescent solar concentrators and tunable lasers is considerable It has been shown that Cr(III) exhibits exceptionally high quantum efficiency of luminescence in these materials as compared to glasses of the same compositions . Cr is also used as a probe for nucleation of and crystallization of cordierite into glass-ceramics . ... 

The variety of emission lines in the gahnite-like glass-ceramics and the possibility to ascribe these lines to various Cr " centers can be a useful tool in following the mechanisms of the nucleation of glass-ceramics doped by Cr(III). The high quantum efficiency of Cr(III) emission in glass-ceramics and the proximity of T2 and levels in the distorted sites may have importance in designing tunable lasers. 

The dissolution rate of zircon in water (Soxhlet tests) decreases from 4.1x10 at 250 to 4.6x10 g/(m xday) at 90 °C [184]. Synthetic ceramics doped with of 6 to 10 wt.% Pu were produced [185]. Leach rates of Pu (MCC-1, 90 °C) were found to be 7x10 (sample with 6 wt.% Pu) and 0.2 g/(m xday). In the sample with 10 wt.% Pu, extra PUO2 was also present. Zircon is amorphized at a dose of 10 a-events/g or 0.6 dpa [72,186,187] and exhibits significant volume expansion (by 18-20%). This leads to microcracking [188] and an increase of the leach rate. Zircon has a rather low capacity with respect to trivalent actinides... 

PREPARATION AND INVESTIGATION OF TRANSPARENT YAG CERAMICS DOPED WITH d IONS... 

We tried to obtain YAG optical ceramics doped with other d ions and to investigate properties of the samples. Ti ion can be a possible d dopant for YAG, and absorption and luminescence spectra of Ti were reported to resemble Ti3 spectra in sapphire It was found that Ti distribution in YAG depends strongly on crystal growth atmosphere, with appearance of precipitates in some cases. The situation can change in case of ceramics. So we decided at the beginning to investigate YAG Ti ceramics as well as YAG with less usual d dopant - Zr. ... 

Preparation and Investigation of Transparent YAG Ceramics Doped with d Ions... 

Transparent colored YAG ceramics doped with Ti and Zr ions as possible broad-band materials for tunable and ultra-short pulses lasers were obtained. The procedure of doped ceramics fabrication included chemical co-precipitation, precursors heat treatment, YAG powder grinding, high pressure colloidal slip-casting for nanopowders compaction and vacuum sintering of performs at 1730-1800 C. Absorption spectra of Zr ceramics samples are similar to the spectra of correspondingly doped YAG single crystals. Zr luminescence was observed for the first time. Possibility to obtain laser action is discussed. 

Dense ceramic (doped High purity H2 Low purity hydrogen Requires significant cooling of IGCC exhaust gas Inadequate electronic conductivity... 

F. 2.6 Photographs of representative Y2O3 ceramics doped with different levels of Zr02, processed through the eombination of slip casting and vacuum sintering. Reproduced with permission from [103]. Copyright 2010, Elsevier... 

Optical properties of Y2O3 ceramics, doped with rare-earth ions, are of special interest for some applications, such as solid-state lasers and scintillators [95]. Luminescence properties, such as upconversions, are also of special significance. For instance, REA"b co-doped Y2O3 transparent ceramics (RE = Er, Ho, Pr and Tm), exhibited very efficient NIR-visible upconverters [96]. 

Fig. 8.7 Variation in microstructure of Nd YAG ceramics doped with a small amount of SiOa sintered at 1780 °C for 0, 2, and 5 h. Reproduced with permission from [61], Copyright 2007, Elsevier...

Qualitative models involving upconversion of excitation to the charge transfer band and then to the conduction band of the materials, including the involvement of transient or permanent Yb " centers, have been reported [223, 224], whereas a quantitative explanation of the observed effects has not been available. According to the thermal effects of the Yb YAG ceramics doped with 10 and 20 at.% Yb at different intracavity intensities, the presence of an additional nonlinear effect at high Yb concentrations and high excitations has been confirmed [221]. 

Fig. 2.61 Tensile ductility of fine-grained iron carbide as function of the Zener-Hollomon parameter is compared with some superplastic ceramics doped with various impurities. The strain rate sensitivity parameter is in the range m = 0.5-0.6 [28]. With kind permission of Elsevier...

Kakimoto, K, Masuda L, Ohsato, H., (2004). "Ferroelectricity and Solid-Solution Structure of KNbOs Ceramics Doped with La and Fe" Key Eng. Mater., 269, pp. 7-10. 

---