Subsolidus phase relations and crystal structure of compounds in the PrO x–CaO–CuO system

Abstract

The subsolidus phase relations of the PrO x –CaO–CuO pseudo-ternary system sintered at 950–1000°C have been investigated by X-ray powder diffraction. In this system, there exist one compound Ca 10Pr 4Cu 24O 41, one Ca 2Pr 2Cu 5O 10-based solid solution, seven three-phase regions and two two-phase regions. The crystal structures of Ca 10Pr 4Cu 24O 41 and Ca 2Pr 2Cu 5O 10-based solid solution have been determined. Compound Ca 10Pr 4Cu 24O 41 crystallizes in an orthorhombic cell with space group D 2 h 20− Cccm, Z=4. Its lattice parameters are a=11.278(2) Å, b=12.448(3) Å and c=27.486(8) Å. The crystal structure of Ca 2Pr 2Cu 5O 10-based solid solution is an incommensurate phase based on the orthorhombic NaCuO 2 type subcell. The lattice parameters of the subcell of the Ca 2.4Pr 1.6Cu 5O 10 are a 0=2.8246(7) Å, b 0=6.3693(5) Å, c 0=10.679(1) Å, and those of the orthorhombic superstructure are with a=5 a 0, b= b 0, c=5 c 0. The Ca 2.4Pr 1.6Cu 5O 10 structure can also be determined by using a monoclinic supercell with space group C 2 h 5− P2 1/ c, Z=4, a=5 a 0, b= b 0, c=c 0/ sin β and β=104.79(1)° or 136.60(1)°, V=5 a 0 b 0 c 0.