Synthesis, second-harmonic generations (SHG), and photoluminescence (PL) properties of Ca₄Bi_6-<i>x</i>Ln_<i>x</i>O₁₃ (Ln=La and Eu) solid solutions

다국어 초록 (Multilingual Abstract)

<P><B>Abstract</B></P> <P>Noncentrosymmetric (NCS) Ca<SUB>4</SUB>Bi<SUB>6-<I>x</I> </SUB>Ln<SUB> <I>x</I> </SUB>O<SUB>13</SUB> (Ln=La and Eu; <I>x</I>=0, 0.06, and 0.12) solid solutions have been synthesized through conventional solid state reactions by using CaCO<SUB>3</SUB>, Bi<SUB>2</SUB>O<SUB>3</SUB>, and Ln<SUB>2</SUB>O<SUB>3</SUB>. Crystal structures of the reported materials have been determined by powder X-ray diffraction using Rietveld method. Ca<SUB>4</SUB>Bi<SUB>6-<I>x</I> </SUB>Ln<SUB> <I>x</I> </SUB>O<SUB>13</SUB> solid solutions crystallizing in the polar NCS space group, <I>C</I>2<I>mm</I> (No. 38), are composed of uni-dimensional bands with BiO<SUB>3</SUB> and BiO<SUB>5</SUB> polyhedra. Second-harmonic generation (SHG) measurements, using 1064nm radiation, indicate that Ca<SUB>4</SUB>Bi<SUB>6-<I>x</I> </SUB>Ln<SUB> <I>x</I> </SUB>O<SUB>13</SUB> solid solutions are type-I phase-matchable and reveal moderate SHG efficiencies ranging from 30 to 80 times that of α-SiO<SUB>2</SUB>. Detailed structure-SHG property relationship analyses suggest that the net moment arising from the alignment of the asymmetric polyhedra of the lone pair cation, Bi<SUP>3+</SUP> in Ca<SUB>4</SUB>Bi<SUB>6-<I>x</I> </SUB>Ln<SUB> <I>x</I> </SUB>O<SUB>13</SUB> solid solutions is critical for the observed SHG phenomena. Photoluminescence (PL) properties measurements on Ca<SUB>4</SUB>Bi<SUB>6-<I>x</I> </SUB>Eu<SUB> <I>x</I> </SUB>O<SUB>13</SUB> solid solutions reveal the characteristic narrow emission lines attributable to <SUP>5</SUP>D<SUB>0</SUB>→<SUP>7</SUP>F<SUB> <I>j</I> </SUB> (<I>j</I>=4, …, 0) transitions and confirm the unsymmetrical coordination environment of the doped-Eu<SUP>3+</SUP> cation sites. Further PL measurements at different temperatures suggest that while Ca<SUB>4</SUB>Bi<SUB>6-<I>x</I> </SUB>Eu<SUB> <I>x</I> </SUB>O<SUB>13</SUB> exhibit the nonradiative emissions at high temperatures, the solid solutions show the radiative emissions with strong intensities at low temperatures.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Noncentrosymmetric calcium bismuth oxide solid solutions, Ca<SUB>4</SUB>Bi<SUB>6-<I>x</I> </SUB>Ln<SUB> <I>x</I> </SUB>O<SUB>13</SUB> (Ln=La and Eu) are synthesized. </LI> <LI> The net polarization originating from the lone pair cation, Bi<SUP>3+</SUP> is critical for the SHG efficiencies of the solid solutions. </LI> <LI> Ca<SUB>4</SUB>Bi<SUB>6-<I>x</I> </SUB>Eu<SUB> <I>x</I> </SUB>O<SUB>13</SUB> reveal the nonradiative and radiative emissions at high and low temperatures, respectively. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>Second-harmonic generations and photoluminescence properties of noncentrosymmetric (NCS) Ca<SUB>4</SUB>Bi<SUB>6-<I>x</I> </SUB>Ln<SUB> <I>x</I> </SUB>O<SUB>13</SUB> (Ln=La and Eu; <I>x</I>=0, 0.06, and 0.12) solid solutions are reported.</P> <P>[DISPLAY OMISSION]</P>