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Large sized Fresnoite Ba 2 TiSi 2 O 8 single crystals were grown by the Czochralski method. Using coordinate transformation methods, the relative dielectric, piezoelectric and elastic constants of Fresnoite Ba 2 TiSi 2 O 8 as a function of orientation were investigated, and their two- and three-dimensional spatial distributions are presented. From them, the maximum values of the piezoelectric coefficients and the corresponding rotation angle can be obtained. The maximum values of coefficients d 22 ∗ , d 23 ∗ , d 24 , ∗ d 32 ∗ , d 33 ∗ and d 34 ∗ were achieved for rotation angles of 40°, 32°, 0°, 58°, 50° and 90°, respectively, and are on the order of 8.7, −4.7, 17.5, 4.7, 8.7 and 17.5 pC/N, respectively. Furthermore, the validity of the electromechanical properties investigation as a function of orientation was verified. The relative dielectric permittivity, elastic constant and piezoelectric coefficient of a ZXl50 o cut rod were calculated and found to be 14.1, 8.7 pC/N and 11.2 pm 2 /N, respectively, in good agreement with the experimental values of 12.7, 9.1 pC/N and 11.7 pm 2 /N. This investigation is important in providing direction for theoretical research and device design of piezoelectric Ba 2 TiSi 2 O 8 crystals.

KDP crystals were grown by the “point seed” rapid growth technique from aqueous solutions with different organic additives, including NTA, HEDTA, EDTA and DCTA. The growth rates were up to about 20 mm/day. The influences of these organic additives on the growth habit and optical properties of these as-grown KDP crystals have been studied. Such organic additives were all found to be able to enhance the solution stability and promote the growth rate for the (100) face of KDP crystals. Furthermore, the UV transmittance and laser damage threshold of the KDP crystals were both increased with the addition of these organic additives. It is proposed that the beneficial influences are due to the chelating action of such organic additives with metal ion impurities in the growth solutions.

A series of potassium dihydrogen phosphate (KDP) crystals were grown by “point seed” rapid growth technique from solutions with different concentrations of cyclohexane diamine tetraacetic acid (CDTA). Effects of CDTA on rapid growth and optical performances of KDP crystals were investigated. The measurement result of laser polarization interference showed that, with increasing the concentration of CDTA in solution, the growth critical supersaturation for the (100) face of KDP crystals decreased continuously, while the growth rate for the (100) face of KDP crystals first increased and then decreased, passing through a maximum. The addition of an appropriate amount of CDTA enhanced the solution stability, increased the UV transmittance and the laser damage threshold, and mitigated the light scattering of these as-grown KDP crystals. However, excess addition of CDTA had adverse effects. The effects of CDTA on the rapid growth and optical properties of KDP crystals are discussed in terms of the chelation of CDTA with impurity metal ions and adsorption of CDTA molecules onto the faces of KDP crystals.