Evaluation of high quality berlinite crystals grown in sulphuric acid medium

This investigation concerns berlinite crystal growth in sulphuric acid solvent through the reverse temperature gradient method and its consequences on crystalline quality and piezoelectric characteristics. Systematic study of growth parameters shows a high sensitivity of growth rates to crystal growth temperature, temperature gradient and acid concentration. The choice of good crystal growth conditions allows us to obtain crystals with a very good crystalline quality checked by X-ray topography. The -OH content, followed by infrared spectrometry, has been lowered to very small values and then electrical measurements of Y and Y-rotated resonators lead to high Q factors, first and second order temperature coefficients lower than those of quartz and a favourable coupling coefficients. For extensional bars, the existence of compensated cuts is also demonstrated.