CBE Research Report Spring 2016 | Page 42

Poster Presentation 31 Crystal Growth of Elpasolite K2PbCu(NO2)6 in Gel Lianyang Dong Department of Chemical & Biomedical Engineering, FAMU-FSU College of Engineering, Florida State University, Tallahassee, Florida, USA The non-conducting hexanitro copper compound K2PbCu(NO2)6 has attracted special interest because it exhibits successive phase transitions at 281 K and 273 K due to the cooperative Jahn-Teller effect1-5. In K2PbCu(NO2)6, The spins from Cu are weakly interacting due to the long contact distance (7.55Å) between Cu atoms, so low temperature ordering effects are expected. Single crystals of K2PbCu(NO2)6 can be grown by slow cooling a saturated aqueous solution containing proper amounts of potassium nitrite, lead acetate and copper nitrate1,4. However, the rapid nucleation rate and convective transport makes it difficult to obtain large high quality single crystals. To reduce the convective transport and high nucleation rate, we grew elpasolite K2PbCu(NO2)6 single crystals in gel. A number of variables were investigated in the growth of K2PbM(NO2)6 crystals in gels: the pH before gel formation, the concentration of reactants, the choice of where to disperse the reactants, and the type of tube to use during the experiments. All growth experiments were carried out at room temperature. The U-tube setup with a neutral gel tended to produce large single crystals up to 2 mm cubes for K2PbCu(NO2)6 (figure. 1.). Figure. 1. K2PbCu(NO2)6 single crystal References 1. Noda, Y.; Mori, M.; Yamada, Y. Successive Jahn-Teller Phase-Transitions in K2PbCu(NO2)6. J. Phys. Soc. Jpn. 1978, 45, 954-966. 2. Kashida, S.; Kaga, H. Effect of Hydrostatic-Pressure on Successive Phase-Transitions in K2PbCu(NO2)6. J. Phys. Soc. Jpn. 1978, 44, 930-932. 3. Kashida, S. Successive Jahn-Teller Phase-Transitions in K2PbCu(NO2)6. J. Phys. Soc. Jpn. 1978, 45, 414421. 4. Kashida, S. Ultrasonic Velocities of K2PbCu(NO2)6 Near the Cooperative Jahn-Teller Phase-Transitions. J. Phys. Soc. Jpn. 1978, 45, 1874-1879. 5. Kashida, S. Effect of Uniaxial-Stress upon the Successive Phase-Transitions in K2PbCu(NO2)6. J. Phys. Soc. Jpn. 1979, 47, 1134-1140. 41 | P a g e