Inorg. Chem. 2006, 45, 2779−2781
Phase Transitions and Second-Harmonic Generation in Sodium
Monothiophosphate
Nathan J. Takas and Jennifer A. Aitken*
Department of Chemistry and Biochemistry, Duquesne UniVersity, Pittsburgh, PennsylVania 15282
Received November 23, 2005
Oxythiophosphate compounds, which contain anions comprised
of oxidized phosphorus bound to oxygen and sulfur, are scarce
3 3
Although the crystal structure of R-Na PO S has been
1
1
solved using neutron powder methods, recent solid-state
NMR experiments have introduced the possibility of disorder
and, in general, poorly characterized. Although
3 3
R-Na PO S has
1
2
in this structure. Although no direct structural information
is offered in this paper, indirect evidence confirming the
noncentrosymmetry of the structure (see Figure 1) is offered
by the determination of the second-harmonic-generation
been known for over 60 years, little has been revealed about this
compound. Here we present thermal analysis and second-
harmonic-generation (SHG) efficiency of
its transformation to the high-temperature
Under vacuum, -Na PO S undergoes one endothermic event at
53 C upon heating and two exothermic events at 504 and 467
C upon cooling. -Na PO S can be trapped upon quenching
Na PO S from high temperature. We have observed that the
phase converts back to the phase at room temperature.
Interestingly, relative humidity has been determined to catalyze
this phase transformation. -Na PO S oxidizes at 315 C in air to
produce Na and Na SO . Upon exposure to 1064-nm incident
radiation, noncentrosymmetric -Na PO S produces an SHG
efficiency 200 times that of
type 1).
3 3
R-Na PO S. Details about
â
phase are discussed.
(
SHG) properties of the material. The thermal stability of
the material in air as well as in vacuo is also presented.
â-Na PO S, previously reported by Jansen et al., can be
trapped by the quenching samples of Na PO S from high
R
3
3
5
°
3
3
°
â
3
3
3
3
â
12
3
3
temperature. We present the first report of a phase transition
from the â phase back to the R phase at room temperature.
Interestingly, this transition is catalyzed by atmospheric
water, even though neither form of the material is hydrated.
Phase transitions catalyzed by atmospheric water are well-
R
R
3
3
°
P O
4 2 7
2
4
1
3
known in the pharmaceutical literature. These transitions
most often involve conversions between anhydrous and
hydrated states. A few transitions among anhydrous glasses
and anhydrous crystalline states have also been reported. In
these processes, adsorbed water acts as a plasticizing agent,
which lowers the glass transition temperature, enhancing the
molecular mobility to an extent that rapid recrystallization
R
3
3
R-quartz and is nonphase-matchable
(
1
Metal oxythiophosphates are compounds that contain
metals bound to anions comprised of oxidized phosphorus
bonded to oxygen and sulfur. There are few oxythiophos-
phates reported in the literature, with less than 30 compounds
published, to date.2-6 Considering the outstanding structural
(
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1
17-129. (c) Brec, R. Solid State Ionics 1986, 22, 3-30.
diversity and myriad of useful applications that exist for the
related metal phosphates and thiophosphates, such as ion
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5
1
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7
8
9
10
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oxythiophosphates.
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*
To whom correspondence should be addressed. E-mail: aitkenj@duq.edu.
J. Power Sources 1995, 55, 133-141.
(
1) The oxy prefix should not be confused with the oxo prefix, for example,
oxophosphates, where the oxo refers to additional oxygen anions that
are bound to metal ions and not to oxidized phosphorus.
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(
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0.1021/ic0520216 CCC: $33.50
© 2006 American Chemical Society
Inorganic Chemistry, Vol. 45, No. 7, 2006 2779
Published on Web 03/10/2006