Process for preparing a barium titanate film

Claim 1

A process for preparing a tetragonal barium titanate film with a thickness of from about 0.1 millimeter to about 1.5 millimeters, comprising the steps of sequentially: (a) providing a batch comprising from about 46 to about 54 mole percent of a barium compound, from about 18 to about 32 mole percent of a titanium compound, and from about 32 to about 18 mole percent of a boron compound, wherein each of said compounds is calculated on the oxide basis in mole percent and wherein: 1. said barium compound is selected from the group consisting of barium oxide, barium carbonate, barium nitrate, barium oxalate, barium hydroxide, barium peroxide, barium per-hydrateoxide, barium acetate, and mixtures thereof; 2. said titanium compound is selected from the group consisting of titanium dioxide, titanium monoxide, titanium sesquioxide, titanium oxalate, and mixtures thereof; 3. said boron compound is selected from the group consisting of boron oxide, boric acid, metaboric acid, tetraboric acid, and mixtures thereof; 4. said titanium compound, and said boron compound contains less than about 0.1 percent by weight, of impurities, and said barium compound contains less than 1.0 percent, by weight, of impurities; (b) melting said batch at a temperature of from about 1300 to about 1400 degrees centigrade for from about 25 to about 40 minutes until it is molten; (c) reducing the temperature of the molten batch from the temperature of the melt to ambient temperature in a period of less than about 30 seconds, thereby producing glass; (d) placing the glass upon a surface of a polycrystalline isostructural substrate, thereby producing a substrate/glass assembly; (e) subjecting the substrate/glass assembly to a temperature of from about 1150 to about 1250 degrees centigrade for from about 10 to 30 minutes until the glass becomes molten and flows over the surface of the substrate; (f) reducing the temperature of the assembly to from about 950 to about 1,050 degrees centigrade; and (g) maintaining the temperature of the assembly at from about 950 to about 1,050 degrees centigrade for from about 25 to about 60 minutes.