Synthesis, second-harmonic generations (SHG), and photoluminescence (PL) properties of Ca(4)Bi(6-x)Ln(x)O(13) (Ln=La and Eu) solid solutions

Abstract

Noncentrosymmetric (NCS) Ca(4)Bi(6-x)Ln(x)O(13) (Ln=La and Eu; x=0, 0.06, and 0.12) solid solutions have been synthesized through conventional solid state reactions by using CaCO3, Bi2O3, and Ln(2)O(3). Crystal structures of the reported materials have been determined by powder X-ray diffraction using Rietveld method. Ca(4)Bi(6-x)Ln(x)O(13) solid solutions crystallizing in the polar NCS space group, C2mm (No. 38), are composed of unidimensional bands with BiO3 and BiO5 polyhedra. Second-harmonic generation (SHG) measurements, using 1064 nm radiation, indicate that Ca(4)Bi(6-x)Ln(x)O(13) solid solutions are type-I phase-matchable and reveal moderate SHG efficiencies ranging from 30 to 80 times that of alpha-SiO2. Detailed structure-SHG property relationship analyses suggest that the net moment arising from the alignment of the asymmetric polyhedra of the lone pair cation, Bi3+ in Ca(4)Bi(6-x)Ln(x)O(13) solid solutions is critical for the observed SHG phenomena. Photoluminescence (PL) properties measurements on Ca4Bi6-xEuxO13 solid solutions reveal the characteristic narrow emission lines attributable to D-5(0)-> F-7(j) (j=4, ..., 0) transitions and confirm the unsymmetrical coordination environment of the doped-Eu3+ cation sites. Further PL measurements at different temperatures suggest that while Ca4Bi6-xEuxO13 exhibit the nonradiative emissions at high temperatures, the solid solutions show the radiative emissions with strong intensities at low temperatures.