Electronic structure and properties of RbTiOPO4:Ta crystals

Abstract

RTP crystals doped with four different Ta concentrations were grown by high-temperature solution method. Ta dopants changed the growth habit of RTP and the (100) faces were more developed than the other crystal faces. The chemical composition and electronic structure were analyzed using Electron Probe Microanalysis (EPMA) and X-ray photoelectron spectroscopy (XPS). Ta elements could easily incorporate into RTP crystals from the melt due to the large distribution coefficient. As Ta content increased, the Rb 3d, Ti 2p, P 2p, O 1s XPS spectra showed a shift towards higher binding energy. The relative Ta atomic concentration in RTP:Ta crystals was calculated and it was determined that the molar ratio between Ta and Ti was higher than the nominal ratio. The thermal properties and SHG efficiency were also studied. Ta dopants decreased the transition temperature from the orthorhombic RTP phase to the cubic RTP phase and increased the decomposition temperature of the cubic RTP phase. When the Ta concentration increased to 9 mol%, the specific heat of the doped crystal was 1.5 times that of pure RTP crystal at 300 °C and SHG intensity was improved by 59% when compared with pure RTP. The results show that Ta doping is helpful for improvement of SHG efficiency and increasing resistance to laser irradiation.