Xaar Technology Limited

A piezoelectric thin film element having a first electrode, a second electrode and a piezoelectric thin film between the electrodes, wherein the thin film comprises a laminate having two or more piezoelectric thin film layers and wherein a first thin film layer is doped by one or more dopants and a second film layer is doped by one or more dopants and wherein at least one dopant of the second thin film layer is different from the dopant or dopants of the first thin film layer.

The present invention relates to a method of preparing a solid solution ceramic material having increased electromechanical strain, as well as ceramic materials obtainable therefrom and uses thereof. In one aspect, the present invention provides a method A method of increasing electromechanical strain in a solid solution ceramic material which exhibits an electric field induced strain derived from a reversible transition from a non-polar state to a polar state; i) determining a molar ratio of at least one polar perovskite compound having a polar crystallographic point group to at least one non-polar perovskite compound having a non-polar crystallographic point group which, when combined to form a solid solution, forms a ceramic material with a major portion of a non-polar state; ii) determining the maximum polarization, P max , remanent polarisation, P r , and the difference, P max −P r , for the solid solution formed in step i); and either: iii)a) modifying the molar ratio determined in step i) to form a different solid solution of the same perovskite compounds which exhibits an electric field induced strain and which has a greater difference, P max −P r , between maximum polarization, P max , and remanent polarisation, P r , than for the solid solution from step i), or; iii)b) adjusting the processing conditions used for preparing the solid solution formed in step i) to increase the difference, P max −P r , in maximum polarization, P max , and remanent polarisation, P r , of the solid solution.

The present invention relates to a method for identifying a solid solution ceramic material of a plurality of perovskite compounds which exhibits an electric field induced strain derived from a reversible phase transition, as well as a method for making such ceramic materials and ceramic materials obtainable therefrom. In particular, the present invention is directed to a method of identifying a solid solution ceramic material of at least three perovskite compounds which exhibits an electric field induced strain derived from a reversible phase transition; said method comprising the steps of: i) determining a molar ratio of at least one tetragonal perovskite compound to at least one non-tetragonal perovskite compound which, when combined to form a solid solution, provides a ceramic material comprising a major portion of a tetragonal phase having an axial ratio c/a of greater than 1.005 to 1.04; and ii) determining a molar ratio of at least one additional non-tetragonal perovskite compound to the combination of perovskite compounds from step i) at the determined molar ratio which, when combined to form a solid solution, provides a ceramic material comprising a major portion of a pseudo-cubic phase having an axial ratio c/a of from 0.995 to 1.005 and/or a rhombohedral angle of 90±0.5 degrees.