Abstract
	Ultrasonic Contact Impedance (UCI) method is an experimental method for indirect measurement of hardness. It enables also an indirect measurement of Young's modulus, E, (modulus of elasticity). Previous experiments on sialons, ZrO2, Al2O3 show a good agreement of Young's modulus values measured by UCI method with the results obtained by other methods.
	A Vickers diamond is attached to one end of a magnetostrictive metal rod. The diamond tipped rod is excited to its natural frequency by a piezoelectric converter. The resonant frequency of the rod changes as the free end of the rod is brought into contact with the surface of a tested specimen. The change in the frequency, ?f, is proportional to the surface area of the indentation. This relation depends also on elastic properties (given by E) of the system "indenter - specimen". 
	The experiments were carried out on Si3N4 cutting tool inserts by an ultrasonic hardness tester MICRODUR 2. In the first step, the common Vickers measuring method was used, we obtained HV 5 = 14,4 GPa. Then the ultrasonic values HVUCI using the ultrasonic hardness tester were measured. Finally, the Young's modulus of tested ceramics was calculated, EP = 200/(1,222.k-0,222), with k = (HVUCI/HV)1/2, resulting in EP = 264 GPa.  This value is in a good agreement with published literature data. 
	The introduced method is easy to operate and fast, don't require special specimen, the surface of tested samples should be of the same quality as for ceramografic analysis.