Growth of cubic KTa1−xNbxO3 crystal by Czochralski method

Abstract

Cubic KTa_1−xNb_xO₃ (KTN) single crystals with different compositions have been grown by the Czochralski technique in a KTaO₃–KNbO₃ solid-solution system. The growth habit, morphological features, and other basic properties of the KTN crystal are discussed. The composition of the crystals was measured by electron probe microanalysis. The Nb composition of the crystals is x(Nb) =0.14, 0.19 and 0.33, corresponding to three different raw materials ratios: Ta₂O₅:Nb₂O₅ (mol)=0.65:0.35, 0.55:0.45 and 0.35:0.65, respectively. The corresponding segregation coefficients are α_Nb=0.400, 0.402, and 0.508, respectively. X-ray diffraction results show that the crystals belong to the cubic phase, with lattice parameters a=4.00289, 4.00251 and3.99279 Å, corresponding to compositions x(Nb)=0.14, 0.19, 0.33, respectively. The transmittance spectra of the crystals show that they have a broad transparent wavelength range from 385 to 3200 nm, except for an absorption band near 2865 nm. The electro-optical coefficient of the crystals was measured by using a Mach–Zehnder interferometer.