| Budget Amount *help |
¥2,400,000 (Direct Cost: ¥2,400,000)
Fiscal Year 1986: ¥100,000 (Direct Cost: ¥100,000)
Fiscal Year 1985: ¥2,300,000 (Direct Cost: ¥2,300,000)
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| Research Abstract |
DSC measurements with the purpose of searching for new materials exhibiting structural phase transitions revealed that (1) <TlH_2AsO_4> shows a peak, which seems to be associated with a phase transition, at -18゜C with an area of <about> 0.2 cal/g. (2) <Tl_3H(SeO_4)_2> has a peak at the onset temperature of 393゜C with an area of <about> 0.8 cal/g. (3) <CsH_3(SeO_3)_2> shows a new peak at the onset temperature of around -37゜C on cooling and at that of -10゜C on heating with an area of <about> 0.02 cal/g, in addition to the known -128゜C antiferroelectric phase transition.
The distortions of the <PO_4> tetrahedra of acid phosphate groups <H_nPO_4> (n=1-3) have been studied by examining the correlations of the P-O bond lengths, OPO angles, O-O lengths and Baur's distortion indices with the hydrogen-bond length O-H・・・O. The main conclusions are summarised as (1) all three distortion indices correlate with O-H・・・O, indicating that the <PO_4> distortion becomes larger with an increase in O-H・・・O. (2) Some of average or indevidual P-O bond lengths and OPO angles and O-O lengths also correlate with O-H・・・O. (3) The mean value of P-O, OPO and O-O are reasonably constant in each <H_nPO_4> type, most notably in the case of OPO. (4) <HPO_4> shows clearer correlation than <H_2PO_4> . (5) The dependence of the <PO_4> distortion on O-H O can be described approximately by a model in which the P atom shifts away from the centroid of the regular tetrahedral framework, while retaining 3m symmetry for <HPO_4> -type structure and mm2 for <H_2PO_4> -type structures.
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