Alkaline niobates KxNa1-xNbO3 represents a class of materials with manifold functional properties. While NaNbO3 is antiferroelectric at room temperature, the addition of small amounts of K results in a solid-solution with ferro-/piezoelectric properties. However, strictly speaking, this only applies to bulk materials.
In heteroepitaxial films, lattice strains can easily be incorporated, which is shown to a have a strong impact on the functional properties of oxides. In this talk, amongst others, this will be discussed for the antiferroelectric NaNbO3 compound. The application of tensile in-plane lattice strain results in the formation of regularly arranged ferroelectric stripe domains. In contrast, compressively strained NaNbO3 thin films exhibit relaxor behavior and a large shift of the phase transition to lower temperatures. Further examples are given for strained KxNa1-xNbO3 epitaxial films grown by metal-organic vapor phase epitaxy and pulsed laser deposition on different rare-earth scandate substrates.