Structure and properties of KTi1-xZrxOAsO4 (x=0.025, 0.05, 0.075, 0.1) crystals

A series of single crystals of solid solutions KTi_1-xZr_xOAsO₄ (x = 0.025, 0.05, 0.075, 0.1) have been grown by the Czochralski method. The structural analysis of this series of samples showed that at titanium partial substitution (0.025 ≤ x ≤ 0.1) Zr⁴⁺ occupies the T1 position of the Ti1O₆ octahedron, as well as the T2 position of the Ti2O₆ octahedron, at the same time the volume of octahedra increases. But at 0.05 ≤ x ≤ 0.1 the volume of the Ti1O₆ octahedron stops growing, and only the volume of Ti2O₆ increases, consequently, at x = 0.05 Zr saturation is observed at position Ti1. The Raman spectrum of a pure KTA crystal is very different from the spectra of the entire range of solid solutions. In the transmission spectrum of samples with partial substitution of titanium atoms by zirconium atoms, there is practically no wide absorption band at 3.5–4 μm typical for pure KTA, the maximum crystal transparency in this region is achieved for x = 0.075. It was found that the introduction of large Zr ions into the KTiOAsO₄ structure leads to a distortion of the lattice and an increase of the band gap.