Subsolidus phase relations in CaO–In 2O 3–B 2O 3 system and crystal structure of CaInBO 4

Abstract

Subsolidus phase relations of CaO–In 2O 3–B 2O 3 system have been investigated mainly by the conventional solid-state reaction technique and powder X-ray diffraction method. There are nine definite three-phase regions under present experimental conditions. Six binary compounds and one ternary compound were found to exist in this system. Crystal structure of the ternary compound CaInBO 4 was determined from X-ray powder diffraction data using Rietveld method. It crystallizes in the orthorhombic space group Pnma (No. 62) with a = 10.3120(3) Å, b = 3.42519(8) Å, c = 9.5150(3) Å, V = 336.07(2) Å 3 and Z = 4. Mixed occupancies were confirmed in this structure, Ca and In atoms are distributed between two atom sites: 93.6%Ca and 6.4%In occupy one site, 93.6%In and 6.4%Ca occupy another. Two In(Ca)O 6 octahedra and two Ca(In)O 7 polyhedra are linked each other by sharing edges to form ribbons in the a– c plane and extend infinitely along the direction of the b axis. The infrared spectrum of CaInBO 4 has been measured, which is consistent with the crystallographic study. In general, compounds MRBO 4 (M and R are divalent and trivalent cations, respectively) are in a large family of monoborates with different structure types strictly depending on the relative size of the M and R ions.