High density ferroelectric Na0.5K0.5NbO3 ceramics : preparation and applications

Abstract: This thesis describes the production of high density ferroelectric Na0.5K0.5NbO3-ceramics (NKN). The main steps in the production are milling, calcination, pressing and sintering. To produce a full dense ceramic material several of these steps have to be considered. In milling the main concern is to produce a powder with small grains and a normally distributed range of grain size. This is done to achieve an optimal packing arrangement with a minimum of porosity. Several different milling techniques and milling parameters such as milling additives and milling media are also discussed. Sintering of the ceramics may be performed in a conventional furnace with or without special atmosphere, so called pressureless sintering. Another method is hot isostatic pressing which is a combination of high isostatic pressure and high temperature; this gives a more efficient sintering. Both methods are discussed here. Paper I describes sintering conditions of NKN produced with different sintering techniques, the results show high density and good ferroelectric properties. Paper II describes the production and properties of thin films laser deposited on different substrates from high dense ceramic targets. Paper III also describes properties of laser deposited thin films on different substrates.