Large Difference in Nonlinear Optical Activity of Rare Earth Ion Substitution of Bi 3+ in A 3 TeBO 9 (A = Bi, La, Pr, Nd, Sm-Dy).

A series of oxides with high rare earth contents, RE 3 TeBO 9 (RE = La, Pr, Nd, Sm-Dy), were synthesized, and they all crystallize in the noncentrosymmetric space group P 6 3 resembling that of a previously reported Bi 3 TeBO 9 ( J. Am. Chem. Soc. 2016 , 138 , 14190-14193), which showed a very strong second harmonic generation (SHG) signal believed to come from all three structural units [BO 3 ], [TeO 6 ], and [BiO 6 ]. Surprisingly, compared with the isostructural compound Bi 3 TeBO 9 , both theoretical calculations and powder SHG tests show that RE 3 TeBO 9 has an abnormally small SHG effect (0.2 × KDP). Based on the group theory analysis, the possible reasons are attributed to the misalignments and lack of distortions of the [BO 3 ], [TeO 6 ], and [REO 8 ] groups in the unit cell. The 2 1 symmetric operation (a subset operation of the 6 3 -screw axis) of the [TeO 6 ], [BO 3 ], and [REO 8 ] groups leads to complete cancellation of their contributions to the xy directions, while the absence of lone pair electrons in RE 3+ and Te 6+ results in small distortion in the c axis, hence small contributions to the SHG coefficients d ijk involving the z axis. Diffuse reflectance spectra of RE 3 TeBO 9 (RE = La, Pr, Nd, Sm-Dy) show typical absorption of different RE 3+ , and the similarity of their infrared spectra is due to the same crystal structure and same structural units of the [TeO 6 ] and [BO 3 ] groups. The strong fluorescence intensities of Eu 3 TeBO 9 and Tb 3 TeBO 9 show the characteristic emissions of Eu 3+ and Tb 3+ , which may serve as luminescence materials with proper doping.