摘要:

It has been reported that synthetic quartz can be unlike natural quartz with regard to its behaviour as a mechanical resonator. In particular, differences may be observed in the frequency/temperature characteristics and Q-factor of AT-cut synthetic-crystal units. These derive from imperfections in the quartz structure, the concentrations of which are known to depend critically upon certain physical-chemical growth conditions.Recently it has been demonstrated that the electrolysis of synthetic quartz results in the effective elimination of those imperfections which, in terms of the acoustic behaviour of synthetic quartz, sets it apart from the natural material. Specifically, the so-called 50° K and 300° K defects are removed, the latter defect being common to fast-grownZ-growth quartz (material grown on a seed surface oriented perpendicular to theZ-axis). Beyond this, however, electrolysis is found to effect a unique improvement in the performance of synthetic and natural quartz at high temperatures. The Q-factor of an AT-cut resonator operating at 500° C is reported to be 5 × 105, representing an improvement of at least two decades above previously recorded values. An analysis of these results is given, together with a discussion of the significance of this discovery in relation to frequency control.

DOI:10.1049/pi-b-2.1962.0053

出版商:IEE    

年代:1962

数据来源: IET

摘要:

The flexural vibrator, designed to vibrate at about 1 kc/s, basically consists of identical cantilever arms extending from a common area to form a symmetrical element. Two distinct shapes have been considered—the H and the ‘zigzag’. Some of the H elements have uniform cross-section while others are arranged to have most of their mass at the free ends in order to reduce the frequency for a specimen of given length. The ‘zigzags’ have folded arms of any number of sections (increasing the number of sections reduces the frequency).The theory of the various forms and their frequency equations are derived. Conditions for perfect balance of the reactions at the supports are discussed.Measurements have been made on H and ‘zigzag’ forms made from quartz slices ZYbΦ(Φ = 0 – 10°) and on ‘zigzag’ form from e.d.t.XYltlΦ, 90°, 90°. Frequency, temperature behaviour, Q-factor and displacement patterns of the elements are compared with theory. Since some of the conventional driving methods proved unsatisfactory a short Section is included on circuits.

DOI:10.1049/pi-b-2.1962.0054

出版商:IEE    

年代:1962

数据来源: IET

摘要:

A new technique for suppressing unwanted resonances in thickness-shear-mode quartz crystals having spherically-bevelled edges has been developed. The technique is based on the fact that the strain associated with inharmonic overtones of vibration extends closer to the perimeter of the crystal along certain axes than along others, while the fundamental thickness-shear mode may, with correct geometry, have negligible amplitude near the crystal perimeter. In view of this it has been found possible, by placing small amounts of an adhesive such as an epoxy resin at certain points on the edge of the crystal, to damp the inharmonic modes selectively without greatly influencing the main response.The new technique permits relatively large variations in electrode diameter to be made without having to alter the crystal geometry to maintain suppression of the unwanted resonances. This facility greatly reduces the problem of crystal-filter design by extending the range of crystal inductances which are available. The paper describes the basic theory underlying the technique, called ‘selective damping’, and illustrates its application to obtain single-response crystals in the frequency range 2–8 Mc/s.

DOI:10.1049/pi-b-2.1962.0055

出版商:IEE    

年代:1962

数据来源: IET

摘要:

Processes for the growth of large crystals of synthetic quartz of piezo-electric quality are now well-established. They all involve the recrystallization of quartz from solution under conditions of elevated temperature and pressure.Two recent developments, which could have profound effect in the future, are described, namely the use of impure nutrients as the source of silica, and the development of a technique for the growth of crystals of the highest possible quality for use in frequency standards and other high-stability applications.

DOI:10.1049/pi-b-2.1962.0056

出版商:IEE    

年代:1962

数据来源: IET

摘要:

The upper frequencies for direct crystal control of oscillators have now been extended to over 100 Mc/s by the development of suitable crystals and circuits. The processes employed for the manufacture of these precision overtone oscillator plates are outlined and details of the methods of inspection are given. The measurement of electrical parameters is discussed and a new test set described. It is probable that at the very high frequencies complete packaged oscillators will be required. Details of such a unit are given.

DOI:10.1049/pi-b-2.1962.0057

出版商:IEE    

年代:1962

数据来源: IET

摘要:

The need for microminiaturization is discussed and the three main approaches to this are briefly described. The problem of the manufacture of a highly reliable microminiature digital integrator using transistors and the microcircuit technique is discussed and the circuit reliability consideration analysed. The microminiature transistor and diode are described and the design of passive components considered under the headings: substrates, resistors, conductors and capacitors, and some of their properties are described. Finally, a brief outline of the special problems of interconnection and encapsulation is given.

DOI:10.1049/pi-b-2.1962.0059

出版商:IEE    

年代:1962

数据来源: IET

摘要:

Microminiaturization work at Government establishments and under Government sponsorship by commercial firms and research organizations is reviewed. It is shown that sponsored research and development is limited to the microcircuit and solid-circuit systems of micro-miniaturization. The relative advantages and disadvantages of the three microminiaturization systems are outlined.

DOI:10.1049/pi-b-2.1962.0060

出版商:IEE    

年代:1962

数据来源: IET

摘要:

The ferro-electric and piezo-electric properties of polycrystalline solid solutions of lead titanate and lead zirconate are reviewed. Major variations in dielectric and electro-mechanical properties obtained by substitution of ions different in valency from the major components are presented, and a theory explaining these variations on the basis of a lattice vacancy-hole equilibrium is outlined.

DOI:10.1049/pi-b-2.1962.0062

出版商:IEE    

年代:1962

数据来源: IET

摘要:

The results of investigations into the design and performance of composite resonators, for use in electric wave filters in the frequency range 15–30 kc/s, are reported. Each resonator comprises a ferro-electric ceramic element bonded between two metal rods so as to form a half-wavelength resonator. By using metal having a low temperature coefficient of elastic modulus, the frequency/temperature stability of the resonators can be restricted to a few parts per million per degree Celsius over the range 10–50° C. Ageing of the electrical parameters at present imposes limitations on the use of such resonators which, by comparison with low-frequency quartz crystals, offer advantages of cheapness, simplicity of manufacture and low capacitance ratios.

DOI:10.1049/pi-b-2.1962.0063

出版商:IEE    

年代:1962

数据来源: IET

摘要:

The maximum speed of switching of ferro-electric crystals is discussed in the light of recent experiments on the switching mechanism. Domain nucleation is studied by experiments with liquid electrodes and by calculations for solid electrodes. The relation of nucleation to domain growth is discussed, and expressions are derived for the attainable speed. Deficiencies in our present understanding are pointed out for further study. It is concluded that startling improvements are not to be expected, but recommendations are given for achieving the best speed.

DOI:10.1049/pi-b-2.1962.0064

出版商:IEE    

年代:1962

数据来源: IET