Some of the piezoelectric crystal can be calcined into the polycrystal ceramics, though there is a spontaneous polarization in each of the fine crystals in the piezoelectric ceramics which is cancelled as a whole and shows no piezoelectricity.
But when a high D.C. voltage is applied to such ceramics, the directions of the spontaneous polarizations are brought to an uniformity and a ferroelectricity ceramics is attained. With some additives, the material with extremely stable frequency, temperature and aging characteristics is being used by TOKEN for ceramic filter.
Compared with the single crystal, the piezoelectric ceramics has various advantageous features as follows :
Ceramic resonators use the mechanical resonance of piezoelectric ceramics. The oscillation mode varies with resonant frequency. The table of Ceramic Resonator Vibration Mode relationship with Frequency Range shows Flexural mode, Length mode, Area expansion mode, Radius vibration, Shear thickness mode, Thickness expander mode, and Surface acoustic wave.
As a resonator device, quartz crystal is well-known. RC oscillation circuits and LC oscillation circuits are also used to produce electrical resonance. The following are the characteristics of PIEZO-CERAMIC.
High stability of oscillation frequency stability is between that of the quartz crystal and LC or RC oscillation circuits. The temperature coefficient of quartz crystal is 10–6/°C maximum and approximately 10–3 to 10–4/°C for LC or RC oscillation circuits. Compared with these, it is 10–5/°C at –20 to +80°C for ceramic resonators.
Small configuration and light weight The ceramic resonator is half the size of popular quartz crystals.
Low price, non-adjustment PIEZO-CERAMIC is mass produced, resulting in low cost and high stability. Unlike RC or LC circuits, ceramic resonators use mechanical resonance. This means it is not basically affected by external circuits or by the fluctuation of the supply voltage. Highly stable oscillation circuits can therefore be made without the need of adjustment.
|Name||Symbol||Price||Size||Adjustment||Oscillation Frequency Initial Tolerance||Long-term Stability|
|Quartz Crystal||Expensive||Big||Not required||±0.001%||Excellent|
|Ceramic Resonator||Inexpensive||Small||Not required||±0.5%||Excellent|
Download Piezo Ceramic Resonators & Ceramic Filters in PDF file.