Growth and Evaluation of Single Crystal Bismuth and Related Compounds.

Attempts were made to grow thick single crystals of bismuth titanate by the top seeded solution method. Unfortunately, the authors were unable to overcome the tendency of bismuth titanate to grow in platey form. There is some indication that germanium oxide, and perhaps molybdenum oxide, added to the melt as a flux promotes denser growth. Large, optically clear crystals of gadolinium molybdate were grown by the RF-Czochralski method. Large single crystals of gadolinium molybdate were also grown by the top seeded solution method these had lower strain than the RF-Czochralski grown crystals but showed a slight cloudiness. Ultransonic pulse-echo measurements at 10 MHz have been used to measure the temperature dependence of the diagonal elements of the elastic constant tensor of gadolinium molybdate, Gd2MoO43, in the neighborhood of the ferroelectric phase transformation at 159C. Mixed crystals in the KTaxNb1-xO3 systems have been grown with compositions ranging from KTaO3 to 60 KNbO3. The polarization dependence of the small signal dielectric constant was measured using a low duty factor ac bias technique. Raman scattering was observed in crystals with compositions between 6 and 33 KNbO3. The ferroelectric soft mode was overdamped in the tetragonal and orthorhombic phases of all crystals observed. Author