Integrated ferroelectrics HxLi1-xNbO₃, HxLi1-xTaO₃and Znx/2Li1-xTaO₃formed by ion exchange technique: The crystal structure and optical properties

A method to determine both the a and c lattice parameters of unstrained lithium tantalate and lithium niobate based solid solutions existing in the strained state by examining surface layer structures formed on “rotated” crystal cuts is proposed. This method, as well as the prism coupling technique, has been applied to characterize both structurally and optically the solid solutions HxLi1-xNbO3, HxLi1-xTaO3 and Znx/2Li1-xTaO3 formed by proton-exchange and the nonisovalent ion-exchange technique. It is shown that, depending on exchange and annealing conditions and crystal cuts, many new phases can be identified in these solid solutions. The relationships between the lattice parameters and the index change in all phases of unstrained HxLi1-xNbO3, HxLi1-xTaO3 and Znx/2Li1-xTaO3 solid solutions have been experimentally determined. The regularities of proton exchange in lithium tantalate crystals under different exchange and annealing conditions are studied and various specific features are explained.