Avl Gesellschaft Fur Verbrennungskraftmaschinen Und Messtechnik M.b.h.

Wolfgang Wallnofer

Peter W Krempl

Uwe Posch

Gabriele Voborsky

A piezoelectric crystal element for surface acoustic wave applications with a quartz substrate with at least one substantially planar quartz surface, the planar quartz surface having an epitaxially grown layer of a quartz-isomorphous crystal with the total molecular formula ABO.sub.4, A standing for Al or Ga, and B for P or As, and the quartz surface and the epitaxial layer having approximately the same crystallographic orientation.

Piezoelectric crystal element

In order to obtain large, high-quality crystals or crystal layers of a me orthophosphate, in particular, GaPO.sub.4 or AlPO.sub.4, from a nutrient solution with the use of a seed plate, the proposal is put forward that in the initial phase of the growth process a seed plate of alpha-quartz (.alpha.-SiO.sub.2) be introduced into the nutrient solution, and that fluoride ions (F.sup.-) be added to this solution, at least for formation of the primary crystal layer on the quartz seed plate.

Hydrothermal process for growing large crystals or crystal layers

For surface acoustic wave devices temperature-compensated piezoelectric crystal elements with one or more planar faces are used. An improvement in temperature stability may be expected if the crystal element is made from GaPO.sub.4 and the planar face is defined by Euler angles .lambda. in the range of 0.degree., .mu. in the range of 40.degree. to 75.degree., i.e. preferably 50.degree. to 60.degree., and .theta. in the range of 0.degree..

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Graz, Austria

Wolfgang Wallnofer