The influence of the sample orientation on the effective value of the hydrostatic piezoelectric coefficients dh(i) of Sn2P2S6 crystals has been studied. The hydrostatic piezoelectric coefficients dh(1) and d′h(3), were measured, dh(1)=(244±3) pC/N and d′h(3)=(92±1) pC/N. The hydrostatic piezoelectric coefficient d h(3) for orthogonal axis system was calculated to be dh(3)=(87±2) pC/N. The, optimal orientation of the sample has been found as (Xy l)−20°-cut. Maximal value of the effective hydrostatic piezoelectric coefficient d h(1) equals 260 pC/N. Double rotated samples were also studied. The orientation of the samples insensitive to the pressure has been found. The theoretical mean value of hydrostatic piezoelectric coefficient (d h)mean corresponding to randomly oriented Sn2P2S6 grains in a poled composite has been calculated to be (d h)mean=136 pC/N.
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