Increased photorefractive sensitivity in double-doped KTa_1−xNbxO_3:Fe,Ti

Abstract

Three KTN crystals with different dopant combinations were grown with the top-seeded solution growth method. 6 The first crystal was doped with Metal electrodes were evaporated onto each sample. The KTN:Fe sample measured 5 mm X 5.7 mm X 3.7 mm, the KTN:Ti sample measured 6.4 mm X 6.7 mm X 2.9 mm, and the KTN:Fe,Ti sample measured 3.8 mm X 3.8 mm X 5.5 mm. The chemical composition of each sample was determined with electron microprobe analysis. The results are summarized in Table 1. The Fe and Ti concentrations were below the detection limit of 100 parts in 106 by weight. The Curie temperatures were determined from peaks in the dielectric constant to occur at T, = -8CC for the KTN:Fe sample, T, = -15'C for the KTN:Ti sample, and T, = -28'C for the KTN:Fe,Ti sample. The variations in the Curie temperatures are a result of the differing Ta/Nb concentration ratios.7