The crystal structure of type III KG
d(PO
3)
4 has been solve
d, an
d the relate
d data are presente
d in thispaper. KG
d(PO
3)
4 (KGP) is monoclinic an
d has
P2
1 as space group. Its cell parameters are
a = 7.255(4)Å,
b = 8.356(5) Å,
c = 7.934(5) Å,
![](/images/gifchars/beta2.gif)
ddle"> = 91.68(5)
![](/images/entities/<font color=)
deg.gif">, an
d Z = 2. KGP is characterize
d by infinitepolyphosphate long chains, which run along the [100]
direction an
d are linke
d through ga
doliniumpolyhe
dra. We
determine
d the crystallization region of KG
d0.47N
d0.53(PO
3)
4, an
d compare
d it to those ofKGP an
d KN
d(PO
3)
4 (KNP). The isotherms of the saturation temperature an
d four neighboring phaseswere also
determine
d. Small N
d-substitute
d KGP single crystals free of macroscopic
defects weresuccessfully grown un
der con
ditions similar to those use
d to grow KGP an
d KNP crystals. N
d substitutionon the structure was efficient, an
d its effect was analyze
d. We
determine
d the transparency win
dows ofboth KGP an
d KNP crystals, an
d evaluate
d the optical tensors at room temperature an
d 632.5 nm. Finally,we use
d the Kurtz metho
d to qualitatively measure the secon
d harmonic efficiencies of N
d-substitute
dKGP crystals. The values obtaine
d for all substitutions were similar to those showe
d by KGP an
d KNPan
d at least to that of H
2PO
4 (KDP).