CRYSTAL-GROWTH AND CHARACTERIZATION OF K(TA1-XNBX)O3-SOLID SOLUTIONS

Single crystals of K(Ta1-xNbx)O3 with compositions 0.35 ≤ x ≤ 1 have been grown from a solution of molten KNbO3 + KTaO3 with an excess of K2O. In order to minimize variations in the Nb/Ta ratio, a method was developed to grow crystals at a small temperature gradient and at a low growth rate. To characterize the homogeneity of the crystals, the spatial fluctuations of the Nb/Ta ratio were resolved by electron microprobe analysis. The temperature dependence of the dielectric constant of the whole crystals was measured. The results indicate that the spatial variation of the Nb/Ta ratio cannot explain the dielectric behavior. We suppose that internal stress, caused by the tendency of exsolution in the system KNbO3 - KTaO3, must be taken into consideration. © 1990.