Abstract Na3Bi(PO4)2 exhibits several phase transitions at about 575, 820 and 905°C. The structure was determined at ambient temperature (α-form) and above the first transition (β-form). The α-form cell is monoclinic with a = 19.86(1), b = 5.353(6), c = 13.96(3) A, β = 110.64(7)°, Z = 8, space group P21/ c ; the structure was solved from 3769 independent reflections to an R value, calculated on intensities, of 0.069. The β-form cell is orthorhombic with a = 18.71(3), b = 7.18(2), c = 5.429(7) A, Z = 4, space group Pnam; the structure was solved to an R value, calculated on structure factors, of 0.055 using intensities of 858 unique reflections measured on a single crystal at 650°C. Both structures are related to that of glaserite. At high temperature, one of the PO4 tetrahedra is statistically disordered over two positions related by the m-mirror. Below the transition, ordering of this ion leads to a unit cell of lower symmetry. At the transition, two individuals grow on the two sides of the m-mirror whic...
[1]
J. Wignacourt,et al.
Phase transitions in the Na3PO4-BiPO4 system
,
1988
.
[2]
P. Hagenmuller,et al.
The structures of the Na3Ln(XO4)2 phases (Ln = rare earth, X = P, V, As)
,
1980
.
[3]
S. Chinn,et al.
Crystal structure and fluorescence lifetime of potassium neodymium orthophosphate, K3Nd(PO4)2, a new laser material☆
,
1976
.
[4]
H. Tompa,et al.
The absorption correction in crystal structure analysis
,
1965
.
[5]
G. D. Rieck,et al.
International tables for X-ray crystallography
,
1962
.