# Dielectric dispersion and piezoelectric resonance in benzil single crystals grown by Bridgman-Stockbarger technique

Shankar, MV and Varma, KBR (1996) Dielectric dispersion and piezoelectric resonance in benzil single crystals grown by Bridgman-Stockbarger technique. In: Bulletin of Materials Science, 19 (5). pp. 791-798.

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Large single crystals of an organic nonlinear optical (NLO) material, benzil, have been grown by employing an indigenously built Bridgman-Stockbarger crystal growth system. The dielectric constant $(\epsilon_r)$, dielectric loss tangent (tan 5) and impedance (Z) of these crystals, monitored along the crystallographic a-axis, as a function of frequency in the 100kHz-10MHz range, exhibit sharp resonance effects in the 100-300kHz region. These strong resonance effects are attributed to the piezoelectric nature of the crystal. The origin of the appearance of the sharp peaks in the frequency variation of $(\epsilon_r)$, and tan S is in response to the elastic resonances induced via the externally applied electric field. The resonance peak positions shift towards lower frequencies with increase in temperature as a consequence of the decrease in the stiffness coefficient $(C_{11})$ of the crystal.