Centre National De La Recherche Scientifique

France Telecom

Compagnie D'electronique Et De Piezo-electricite C.e.p.e.

Etat Francais, Represente Par Le Ministre Des Ptt (centre National

Compagnie D'electronique Et De Peizo-electricite Cepe

Aline Goiffon

Etienne Philippot

Jacques Detaint

Maurice Maurin

Yves Toudic

Albert Zarka

Jacquie Schwartzel

Alain Ibanez

Olivier Cambon

Jean-Claude Jumas

Bernard Capelle

Roger Arnaud

Jean-Pierre Aubry

Jean-Claude Doukhan

Daniele Cachau Hereillat

Bernard Cappelle

Quartz sections having a surface condition as polished as possible are prepared by controlled dissolution by placing said quartz sections in a bath of a quartz solvent or a mixture of solvents, wherein the bath is basic and comprises an alkaline hydroxide or fluoride, or ammonium hydroxide, or a mixture of these compounds; and conducting controlled dissolution of the quartz sections at atmospheric pressure.

Controlled dissolution of quartz

The present invention relates to a process for increasing the dimensions of quartz crystals and of quartz-isomorphic materials, which can be produced by hydrothermal growth from seed, in which a seed obtained by assembly of several crystalline plates is used, wherein there are assembled at least two plates of strictly identical lengths and/or widths and of similar thicknesses, cut in at least one crystal and having, on at least three faces crystalline orientations, the deviations from which remain, between the plates, smaller than about 10' of arc, and wherein said plates are brought together on a support by guidance elements, thus ensuring their alignment on the aforementioned three faces while maintaining crystalline orientation deviations smaller than about 10' of arc, one face per plate being left free for growth of the assembled seeds, leading to the production of a single crystal exhibiting at least one dimension greater than that corresponding to the original crystalline plate. The subject of this invention is also to the crystals obtained by this process.

Process for increasing the dimensions of crystals which can be produced

Process for dissolution of a crystalline material

The invention relates to a process for the preparation of berlinite crystals AlPO.sub.4, with a high Q factor, from seeds or crystalline flakes of AlPO.sub.4, by a hydrothermal method. It is characterized in that the crystallization solution is a sulfuric solution of AlPO.sub.4. The invention also relates to the berlinite monocrystals obtained by this process.

Process for the preparation of berlinite crystals with high Q factor

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Saint Clement la Riviiere, France

Aline Goiffon