Phase equilibria in the ternary system Pr-Co-B

The isothermal section at 600 C in the Co-rich ternary Pr-Co-B system was determined by means of X-ray diffraction. In this range, eleven ternary borides were observed: Pr3Co13B2, PrCo4B, Pr5Co19B6Pr3Co11B4, Pr2Co7B3, Pr2Co14B, PrCo12B6, PrCo4B4, Pr2Co5B3, PrCo2B2, Pr2Co5B2. Among the eleven ternary compounds, two had not been reported previously: hexagonal Pr3Co13B2 with a=5.0672(3) A and c=10.6850(6) A and hexagonal Pr5Co19B6 with a=5.1264(4) A and c=16.5602(6) A. The first five borides are members of the homologous series Rm+nCo5m+3nB2n formed by alternative stacking m layers of RCo5 with n layers of RCo3B2 along the c-axis. The Pr2Co5B2 compound belongs to the Rm+nCo2m+3nB2 family which is based on the MgZn2-type and the CeCo3B2-type structures. (orig.)