dongjee33:
Hello.
Is there any qebsite that I could buy ultrasonic transducer?
I find 1.5mhz (or it will find 1.4 or 1.6) long bandwidth frequency transducer.
Or is it possible to make transducer with piezo crystal?
You haven't said what you want to do with this transducer, but for many applications transducers are operated at their resonant frequency to maximize efficiency. Thus you would have to use a piezo device appropriate to your operating frequency. In addition any mounting, enclosure, and interface to the transmit medium will affect the tuning of the piezo device which is very much a non-trivial design task.
That said a wide range of devices is available: Piezo Disc - STEMINC - Piezoceramic Discs, Plates, Transformers, Bimorphs and Cylinders