The experimental study of acoustic waves of frequency ∼ 40GHz

The temperature dependencies of attenuation of: (i) longitudinal and shear waves in lithium niobate, (ii) longitudinal waves in ruby, and (iii) longitudinal and shear waves in magnesium aluminate spinel (spinel) at the frequency 36.5 GHz were measured. For the most crystals and wave types the temperature range was 78- ~150 K, i.e. the strong attenuation did not allow to watch the echo-pulses at the room temperature. The exemption was the shear wave in spinel with the ratio of oxides 1:2, for which we could confidently watch the echo-pulse at 300 K delayed on 0.78 ¿s. The comparison of the attenuation of this wave at frequencies 36.5 GHz (54 dB/mks) and 9.4 GHz (3.5 dB/mks) at 300 K showed the quadratic frequency dependency.