| Abstract
| - The type III crystal structure of KGd(PO3)4 (KGP) has been solved. Type III KGP has an advantage over the isomorphs type IV and type A in that it has a noncentrosymmetrical structure, so nonlinear optical processes may be allowed. Moreover, type III KGP possesses two important features in solid-state laser technology. It has a high doping acceptance of lanthanide ions, and it is prevented from deforming when working above room temperature because of its almost isotropic thermal expansion. Type III KGP is therefore regarded as a promising self-doubling host, which could be used to obtain light all over the UV−vis range to low wavelengths because the UV cutoff is around 180 nm. We analyzed the effect of substituting Gd with Nd on the synthesis and on some structural and optical properties.
- The crystal structure of type III KGd(PO3)4 has been solved, and the related data are presented in thispaper. KGd(PO3)4 (KGP) is monoclinic and has P21 as space group. Its cell parameters are a = 7.255(4)Å, b = 8.356(5) Å, c = 7.934(5) Å, β = 91.68(5)°, and Z = 2. KGP is characterized by infinitepolyphosphate long chains, which run along the [100] direction and are linked through gadoliniumpolyhedra. We determined the crystallization region of KGd0.47Nd0.53(PO3)4, and compared it to those ofKGP and KNd(PO3)4 (KNP). The isotherms of the saturation temperature and four neighboring phaseswere also determined. Small Nd-substituted KGP single crystals free of macroscopic defects weresuccessfully grown under conditions similar to those used to grow KGP and KNP crystals. Nd substitutionon the structure was efficient, and its effect was analyzed. We determined the transparency windows ofboth KGP and KNP crystals, and evaluated the optical tensors at room temperature and 632.5 nm. Finally,we used the Kurtz method to qualitatively measure the second harmonic efficiencies of Nd-substitutedKGP crystals. The values obtained for all substitutions were similar to those showed by KGP and KNPand at least to that of H2PO4 (KDP).
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