Method of producing composite metal oxide material

A method of producing a composite material having a layer of a first metal oxide having the formula:

• LnBa.sub.2 Cu.sub.3 O.sub.y
• wherein Ln stands for Y or an element belonging to the lanthanoid and y is a number of 6-7, said method comprising the steps of:
• providing a seed material including a substrate comprising an alkaline earth metal oxide, and a non-uniformly oriented film with a x-ray diffraction pattern showing a diffraction peak for one axis, which is normal to the plane of the substrate, and additional diffraction peaks, said oriented film having a thickness of 0.01-1 .mu.m and provided over a surface of said substrate, said oriented film being formed of a second metal oxide which has a crystal structure of a Y123 metal oxide and which has the formula:
• LnBa.sub.2 Cu.sub.3 O.sub.y
• wherein Ln stands for Y or an element belonging to the lanthanoid and y is a number of 6-7;
• and
• contacting said oriented film with a liquid phase which contains a melt composed of Cu, Ba and O and in which a solid phase is present at a position separated by said liquid phase from the position at which said oriented film contacts said liquid phase, said solid phase providing said liquid phase with solutes which constitute said first metal oxide so that said solutes are transported to the position at which said oriented film and said liquid phase contact, thereby permitting said first metal oxide to grow on said oriented film as a single crystal.