We report the first Simultaneous measurement of a crystal's complete elastic and piezoelectric coefficients: Cif, eijk. The studied crystal was lithium niobate (LiNbO3) with trigonal crystal symmetry (3 m point group), thus six independent Cijk, four eijk, and two dielectric coefficients Kij. We used a single specimen: an oriented rectangular parallelepiped measuring about 5 mm. Our measurement method, acoustic spectroscopy, focuses on the crystal's macroscopic resonance frequencies, reflecting any property that affects the crystal's macroscopic vibrations. We overcame the principal obstacle to precise measurements-mode misidentification -by using laser-Doppler interferometry to detect the crystal's displacement surface. This approach yields unambiguous mode identification. We considered fifty-six resonances ranging in frequency from 0.3 to 1.2 MHz to deduce inversely Cij and eijk with known Kij. The ten unknowns always converged to the same values even with unreasonable initial guesses. The Cij uncertainty verages 0.09% for the diagonal Cij. The eijk uncertainties average 5%. All our coefficients fall within the (surprisingly wide) error limits of previous (conventional) measurements.
Citation: Journal of Applied Physics
Issue: No. 5
Pub Type: Journals
acoustic spectrosocpy, dielectric coefficients, displacement figure, elastic coefficients, lithium niobate, mechanical waves, piezoelectric coefficients