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

Other

Gunter Engel

Peter W Krempl

Helmut List

Uwe Posch

Alfred Enko

Klaus-Christoph Harms

Hermenegild Mang

Alfred Nitsch

In order to prevent crystal seeds with retrograde solubility from dissolving in the hydrothermal growing solution at the beginning of the growing process, and to protect the finished crystal at the end of the growing process, and in order to reach the thermodynamic growth equilibrium as soon as possible, the proposal is put forward that the growing solution be prepared, pre-saturated and pre-heated to a temperature close to saturation temperature outside of the growing tank, and that, for the growing process proper, the hot growing solution be added to the pre-heated growing tank provided with crystal seeds, where it should be further heated to a temperature at which the crystals start growing, and, further, that the hot growing solution be quickly removed from the growing tank as soon as the growing process has been completed.

Apparatus for growing homogeneous crystals

Method of growing homogeneous crystals

In piecoelectric measuring elements comprising two or more crystal elements that are jointly subject to the mechanical variable to be measured and are provided with electrically conductive electrodes on opposite surfaces located essentially normal to the electric (x) axes of these crystal elements, disadvantages arising from shearing stresses can be prevented by using crystal elements (2) from crystals of point group 32, in which exist two opposite types of enantiomorphism, l and r, in which part of the crystal elements used belong to one of the two enantiomorphic types l or r, and have one of the two absolute orientations of the x-axis, .alpha..sub.1 or .alpha..sub.2, while the remaining crystal elements belong to the opposite enantiomorphic type and have the opposite orientation of the x-axis.

Piezoelectric measuring element

In order to reduce the water content in piezoelectric GaPO.sub.4 crystal elements the proposal is put forward that each GaPO.sub.4 crystal element should be cut in its entirety from one uniform growth zone of a GaPO.sub.4 raw crystal bar and should not contain any zone boundaries, and that the piezoelectric GaPO.sub.4 crystal elements should be treated with a dehydrating solution, until an infrared coefficient of .alpha.&lt;1.5 cm.sup.-1 is obtained at a wavelength in the vicinity of 2.0 .mu.m.

Method and device for reducing the water content in piezoelectric GAPO.sub.

A transducer comprising a flexible piezoelectric layer as a sensor element for measuring mechanical quantities in hollow bodies, above all pressures in pipes, the opposite sides of this layer being bonded to electrically-conductive contact layers and being connectable via leads to a display and evaluation unit. In order to achieve a high temperature stability in such transducers and to make them suitable for use at temperatures exceeding 80.degree. C., the piezoelectric layer is proposed to consist of wurtzite or sphalerite. One of the electrically-conductive contact layers can be of some heat-resistant, flexible supporting material, for instance flexible metal foil, such as Cu-Be foil, or a sheet of plastic, one or both of whose sides are metallized, and the other electrically-conductive contact layer can be a metal coating applied by evaporation.

Transducer with a flexible piezoelectric layer as a sensor element

In a process for producing crystals in crystallographic point group 32 and corresponding to the comprehensive chemical formula APO.sub.4, wherein symbol A is a chemical element taken from the group Al and Ga, P is phosphorus and O is oxygen, from heated solutions of salts of group A in phosphorus acid, the application of acid concentrations within the range of 12.5 to 20 mol/l, solution temperatures within the range of 110.degree. to 190.degree. C. and total pressures within the range of prevailing static vapour pressure to 2.5 bar provides a simple, safe and cost-effective method of producing perfect, flawless crystals.

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Leitring, Austria

Gunter Engel