Abstract: A method is disclosed for growing thermally unstable ferroelectric materials having the formula MH.sub.2 XO.sub.4, where M is potassium, rubidium, cesium or ammonium; H is hydrogen or deuterium and X is phosphorus or arsenic. The ferroelectric material is heated to melt temperature in a constant volume cylindrical chamber (10) which is moisture-free. Improved crystal formation is accomplished by axially cooling the melt from the bottom end (18) of the chamber by thermal conduction along the chamber longitudinal axis predominantly and only minimally by radial thermal conduction through the sides (16) of the chamber. The axial cooling produces a crystal interface which is flat and perpendicular to the chamber axis and which gradually progresses toward the chamber top to provide uniform growth of a single crystal of ferroelectric material.

Abstract: An improved method and apparatus for crystallizing amorphous or polycrystalline material is disclosed. In this invention, a material which is to be crystallized is formed on a substrate and single crystalline seed material is disposed in contact and/or adjacent to or with at least a portion of the material which is to be crystallized. A layer of material which serves as a "wetting agent" is then formed over the material to be crystallized. The structure thus formed is subjected to a heat treatment which melts the material being crystallized and when the material solidifies its crystalline structure is substantially epitaxial based on the seed material. The "wetting agent" layer serves to prevent deleterious balling up of the material during crystallization.