BiCoPO5 is isostructural with BiNiPO5, a = 7.253(1) Angstrom, b = 11.294(1)
Angstrom, c = 5.230(1) Angstrom, beta = 107.82(1)degrees, P2(1)/n, z = 4,
R-1 [I > 2 sigma(I)] = 0.025, R-1 for all reflections = 0.030, Co is in a s
lightly distorted octahedral coordination with Co-O bonds ranging from 2.00
7(5) to 2.150(5) Angstrom. Pi is in six-fold coordination to oxygen in a di
storted octahedral coordination with Bi-O bonds ranging from 2.129(4) to 2.
693(5) Angstrom. The lone-pair electrons are 0.39 Angstrom from the Pi nucl
eus. The PO, tetrahedron is quite regular with P-O bonds 1.532(5)-1.558(5)
Angstrom. Phases in the solid solution series BiNi1-xCoxPO5, 0 less than or
equal to x less than or equal to 1 are monoclinic, Magnetic susceptibility
measurements show that they are all antiferromagnets with T-N varying from
20 K for the pure Ni phase to 15 K for pure Co. The materials are semicond
uctors with E-g = 0.38 ev and E-g = 0.9 ev for the Ni and Co compounds, res
pectively. When monoclinic BiCoPO5 is heated past the melting point to 950
degrees C it decomposes and an orthorhombic phase is formed. Single crystal
Weissenberg photographs of this new phase yield lattice parameters a = 14.
688(3) Angstrom, b = 11.229(2) Angstrom, c = 5.438(1) Angstrom, space group
Ibam or Iba2, (C) 1999 Academic Press.