New advances in crystal growth of high purity berlinite: a new solvent the sulfuric acid

The solubility of berlinite in sulfuric acid as a function of temperature and solvent concentration is studied, and it is found that this solubility is much higher in sulfuric acid than in all other known solvents. The crystal growth parameters were determined for the reverse temperature gradient method in 375 cm³ platinum-lined autoclaves for different values of the crystal growth temperature, the vertical temperature difference, and the acid concentration. Infrared spectrometry was used to monitor the water concentration in crystals, which was found to be principally dependent on the growth rate and the acid concentration. X-ray topography has shown a very low dislocation density. Electrical measurements of resonators of several orientations have shown that the Qf product can exceed 3.5×10¹² and that the first- and second-order temperature coefficients of Y-rotated resonators are lower than those of quartz resonators of corresponding orientations. The AT cut displays a cubic temperature behavior and it was verified that k for the AT cut is twice that for AT quartz