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DIN Standards Committee Optics and Precision Mechanics

Overview

This International Standard applies to synthetic quartz single crystals for the manufacture of piezoelectric elements for frequency stabilization and selection and for optical applications. Quartz crystal for optical applications is in many cases produced by the same manufacturers that produce quartz crystals for electronic applications. The same equipment and processes are used to manufacture quartz crystals for optical applications and quartz crystals for electronic applications. In addition, with few exceptions, the same methods are used to characterize electronic and optical materials. IEC 60758 is therefore the appropriate standard for the inclusion of additional information on quartz crystals for optical applications. The third clause introduces the terms and other clauses include the specification for synthetic quartz crystal, the specification for pre-processed synthetic quartz crystal and the testing of synthetic quartz crystal and pre-processed synthetic quartz crystal. This guide has been prepared at the general request of users and manufacturers in order to make the best possible use of synthetic quartz crystal with all its advantages. This guide is not intended to explain the techniques used in the manufacture of quartz crystal crystals, nor to attempt to describe all the properties of synthetic quartz crystal. Synthetic quartz crystals are grown using the hydrothermal temperature gradient method. At room temperature, a pressure chamber (autoclave) is partially filled with an alkaline growing solution. Crystal nuclei are placed in the upper part and nourishing quartz fragments are placed on the bottom of the autoclave, which is then closed and heated. The temperature in the upper part is kept lower than in the lower part. As a result, the dissolved nutrient material is transported by the convection currents and deposited on the crystal nuclei. The shapes, dimensions and physical properties of the grown crystals depend on the orientation, the dimensions of the crystal nuclei and the growth conditions. Good control of the growing process ensures uniform shapes and dimensions as well as homogeneity of quality. Synthetic quartz crystals "as grown" are surrounded by characteristic growth areas. The usual shape of a crystal grown on a Z-cut crystal nucleus with a small X dimension is shown. Other crystal shapes are produced with Z-cut crystal nuclei of other proportions or crystal nuclei of other cuts. The size of synthetic quartz crystals is determined by the three nominal dimensions X, Y (or Y') and Z (or Z'). These dimensions lie in the directions of the X, Y (or Y') and Z (or Z') axes. These dimensions are chosen so that an economic yield can be achieved both in the growing and in the manufacturing of the quartz components, although it shall be emphasized that the dimensions are subject to agreement between the manufacturer and the user. The informative Annex A deals with frequently used sampling procedures. Whole volume counting is a method used by both manufacturers and users when the control of the concentration of inclusions in quartz crystals is of paramount importance. Each crystal is tested using the inclusion counting method, except that the entire usable volume of the crystal is tested. If the dimension of the crystal in the X direction is greater than the depth of field of the microscope, then care shall be taken when scanning and measuring to ensure that no inclusions are overlooked by adjusting the focal plane in the necessary range. The number of inclusions is recorded for each size range in the entire usable volume of the crystal to be calculated. The concentration of inclusions in the crystal is calculated by dividing the number of inclusions in each size range by the usable volume. Further procedures are the simplified sampling of Y-bars - procedure 1, the simplified sampling of Y-bars - procedure 2 and the application of comparative procedures for a 100% test of crystals. The informative Annex B describes a numerical example. If a stereo microscope with a magnification of 30 times and a field of view of 0.6 cm diameter and 0.1 cm depth of field is used to count the inclusions in six areas over the entire height of a crystal bar with an X dimension of 2.0 cm, then the number of inclusions given in the table is selected. The informative Annex C contains an example for the selection of reference samples. For a reference sample for each class range, some suitable cultured crystal bars are carefully selected as the bars to be tested. If the bars to be tested have crystal nuclei with a large X dimension, then Y-cut slices are sawn from the bars and machined to a thickness of 10 mm with a polished surface. The sample volumes are divided into 1 cubic centimeter pieces on the Y surface within the Z growth zones, with the exception of the crystal nucleus, by drawing squares with an edge length of 10 mm. In the case of a small X dimension, such as a Y bar, the X-cut slices can be obtained by pre-machining and finished to a thickness of 10 mm with a polished surface. By applying 10 mm squares on the X surface within the Z growth zones, excluding the crystal nucleus, the sample volumes are divided into 1 cubic centimeter pieces. A line drawn near the crystal nucleus shall be approximately 0.5 mm from the surface of the crystal nucleus to avoid counting in the veil area of the crystal nucleus. The informative Annex D contains explanations on calipers with measuring tips. Calipers with measuring tips and digital calipers with measuring tips have two movable measuring points and are suitable for measuring specimens with irregular surfaces such as the Z-face of grown synthetic quartz. The informative Annex E describes the compensation of the infrared absorption value alpha. It is known that when alpha values are measured in different laboratories using the methods recommended in this standard and with the same measuring equipment, measurement deviations between laboratories occur which exceed the limits of measurement uncertainty required to ensure compliance with the alpha value requirements of this standard. To solve this problem and to ensure correlation between laboratories, a round robin test was carried out with five test specimens with a wide range of alpha values in twenty laboratories. A procedure was established to determine correction terms based on the differences between the individual results and the mean values of the laboratories at constant wavenumbers and test samples. The procedures described in this Annex can be used in future to determine correction terms. The interlaboratory study used grating infrared spectrometers with dispersive arrangement and FT-IR spectrometers so that the process can be applied to facilities with any measurement method. The informative Annex F explains the differences between the IEC standard and the IEEE standard for the orthogonal axis system for quartz. The IEEE standard 176-1946 was revised in 1978 and published as IEEE standard 176-1987 after further revision in 1987. The main change was the +X direction in the orthogonal crystal axis system. This differs from the current IEC 60758. The informative Annex G explains the agreement between the alpha values determined with the dispersive infrared spectrometer and the Fourier transform infrared spectrometer. In the past, the dispersive infrared spectrometer was mainly used as the measuring device for determining the infrared absorption coefficient (alpha value). However, the dispersive infrared spectrometer, which was used for the measurement method according to Annex E, has generally not been available on the market for a decade. Today, the Fourier transform infrared spectrometer (FT-IR spectrometer) is available for measuring the infrared absorption of materials. The responsible committee is DKE/K 642 "Piezoelektrische Bauteile zur Frequenzstabilisierung und -selektion" ("Piezoelectric and dielectric devices for frequency control and selection") of the DKE (German Commission for Electrical, Electronic and Information Technologies) at DIN and VDE.

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Responsible national committee

DKE/K 642 - Piezoelektrische Bauteile zur Frequenzstabilisierung und -selektion