Na2RE2TeO4(BO3)(2) (RE = Y, Dy-Lu): Luminescent and Structural Studies on a Series of Mixed Metal Borotellurates

The first examples of metal borotellurates, namely, Na2RE2TeO4(BO3)(2) (RE = Y, Dy-Lu) have been prepared by using solid-state reactions. They possess similar structures and crystallize in space group P2(1)/c (No. 14). The compounds feature a novel [RE2TeO4(BO3)(2)](2-) 3D network structure,composed of linear [TeO4(BO3)(2)](8-) anions interconnected by RE3+ ions with the voids of the network filled by : the Na+ fans. They exhibit high thermal stability (higher than 800 degrees C). Results of magnetic measurements on Dy, Ho, and Er compounds indicate that they display weak antiferromagnetic interaction between RE(III) centers. Luminescent studies show that Na2Er2TeO4(BO3)(2) has a strong emission at 1.562 mu m with a wide fwhm (70 nm) and moderate lifetime (0.18 ms), whereas Na2Yb2TeO4(BO3)(2) has a strong NIR region emission around 1.02 mu m. Furthermore, UV-vis-NIR absorption spectra, infrared spectra, and DFT calculations for the Y compound as a representative were also accomplished.