Sol-gel studies of the Yb2O3-Al2O3 system and alumina garnets with ytterbium.

Sol-gel science and techniques have mainly been used to synthesize inorganic oxides. Thousands of inorganic oxides or mixed oxides have been manufactured by the sol-gel method. They can take the form of thin films, powders, monolithic, and fibres. Many sol-gel oxides systems have been studied. One of the most important systems is the Y[2]O[3]-AI[2]O[3] system which has been studied for many years by sol-gel methods. In this system, there are several phases which have widespread uses in industry such as Y[3]AI[5]O[5], YAIO[3], and Y[4]AI[2]O[9]. For example, Nd doped Y[3]AI[5]O[5] is presently the most widely used solid-state laser material. Yb doped YAG is one of the most promising laser active materials and is more suitable for diode pumping than the traditional Nd-doped YAG. In fact, the rare earth aluminium garnet family is one of the most active areas of activities in recent years because of their optical, mechanical, and thermodynamical properties.In this thesis, the production and properties of the sol-gel Yb[2]O[3]-Al[2]O[3] system are studied using sol-gel science and techniques. Ytterbium is a rare earth element in the lanthanide series and belongs to the same group as yttrium in the periodic table and hence, the oxides that they form often have very similar properties and applications in industry. The research focuses on the sol-gel synthesis, sol-gel processing, crystallisation, and structures of alumina garnets in the Yb[2]O[3]-Al[2]O[3] system. The thermal behaviour of the sol-gel Yb[2]O[3]-Al[2]O[3] system was studied by DTA and TG. The crystallisation characteristics were investigated in the pure Yb[2]O[3]-Al[2]O[3] system. The effects of the crystallisation were also studied after other elements were doped in this system. Thin films, thick coatings, and nanosize powders of the pure and doped alumina garnets were produced by the sol-gel method. Their morphologies and structures were studied and consideration was given to their potential uses in industry.In this thesis, novel Mo doped YbAG garnets were synthesised for the first time by the sol-gel technique. Their application depends on the existing state of Mo (VI) cations in the YbAG matrix. Laser materials, Yb doped YbAG garnets, were successfully produced for the first time using the sol-gel method and their structural changes have been studied. The host crystal structures deform after doping with various concentrations of Yb[3+]. However, this deformation does not show a linear relationship with the doped Yb[3+] concentration, which could, in part, explain why around 20 atomic % doped Yb:YAG generally exhibits good properties in laser or scintillator applications.