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|Title:||Effect of variation in frame work composition on the thermal expansivity of NZP phases|
|Authors:||Govindan Kutty, K.V.|
|Keywords:||Anisotropy; Atoms; Composition effects; Crystal lattices; Niobium compounds; Phase transitions; Sodium compounds; Thermal expansion; Thermal stress; Tin compounds; X ray analysis; Chemical bond; Ionic radius; X ray diffraction; Phosphates|
|Citation:||Materials Research Bulletin, 29(10), 1009-1016|
|Abstract:||Two series of NZP compounds, NaM2(PO4)3 and NbM(PO4)3 [M = Ti, Zr, Hf, Sn and Th] have been synthesised and their thermal expansion coefficients in the temperature range 298 - 1273 K determined by using high temperature x-ray powder diffractometry. In the first series, the influence of the M - O bond is clearly seen even in the presence of the large contribution of the Na - O bond to thermal expansion; the expansivity of the lattice is found to vary with the ionic radius of the M atom. This trend is also reflected in the infra-red absorption frequencies of these compounds. In the second series, while the expansion behaviour is found to be dependent on M, the variation of expansivity with M is different from that found in the first series. The tin compounds in both the series display anomalous behaviour. We also report here, for the first time, a phase transformation in NbSn(PO4)3 around 673 K characterized by a maximum and a minimum in the lattice parameters a and c respectively. ? 1994.|
|Appears in Collections:||Articles|
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