Growth, electronic structure and properties of Rb2Ti1.95Yb0.05(PO4)3 crystals

• Rb2Ti1.95Yb0.05(PO4)3 crystals have been grown by high-temperature solution method.
• Two valances of titanium Ti3+ and Ti4+ were coexisting in this crystal.
• The chemical bonding in Rb2Ti1.95Yb0.05(PO4)3 crystals were characterized.
• The thermal and optical properties of Rb2Ti1.95Yb0.05(PO4)3 were also studied.

Rb2Ti1.95Yb0.05(PO4)3 crystals with langbeinite-type structure were grown by high-temperature solution method. The chemical composition and electronic structure were analyzed using inductive coupled plasma atomic emission spectroscopy (ICP-AES) and X-ray photoelectron spectroscopy (XPS). The deconvolution of Ti 2p3/2 photoemission line reveals two peaks at 459.3 eV and 458.1 eV, indicating titanium existence in two valence states: Ti4+ (459.3 eV) and Ti3+ (458.1 eV). The reduced BE difference ΔBE (O 1s-Ti 2p3/2) shows stronger ionicity of Ti–O bonds in Rb2Ti1.95Yb0.05(PO4)3 compared with RbTiOPO4. Additionally, UV absorption, specific heat, and second harmonic generation (SHG) efficiency were studied. The UV absorption edge of the Rb2Ti1.95Yb0.05(PO4)3 crystal was observed at 368 nm. The SHG intensity of Rb2Ti1.95Yb0.05(PO4)3 is 5–6 times greater than that of KDP crystal when the particle size is between 38 and 74 μm.