Mircostructures of LiNbO3:Gd and LiNbO3:Gd,Cu single crystals

Lithium niobate (LN) single crystals were grown by Czochralski at air from platinum crucibles at facility Crystal-2 (Zavod Kristall Ltd, Russian Federation). There were 2 double-doped crystals LiNbO3:Gd,Cu, sample 1 ([Cu]=0.57, [Gd]=0.07 wt%), sample 2 ([Cu]=0.041, [Gd]=0.076 wt%) and 4 single-doped crystals LiNbO3:Gd, sample 3 ([Gd]=0.003 wt%), sample 4 ([Gd]=0.01 wt%), sample 5 ([Gd]=0.05 wt%) and sample 6 ([Gd]=0.26 wt%). Macro- and microstructure of as-grown crystals before turning them to a single-domain state were studied by image analysis system «Thixomet» (optical microscope Axio Observer.D1m (Carl Zeiss, Germany) connected to a camera PixeLink PL-B774U (PixeLink, Canada) and a computer equipped with a program «ThixometPRO» (Thixomet, Russia)). As-grown LN crystals were polished and etched at a room temperature for 20h in a mixture of mineral acids HF:HNO3 = 1:3. Studied plates were X- and Z-cut.