Boron substitution in ternary metal phosphide superconductors

Partial substitution of boron for phosphorus in the ternary phosphide superconductors ZrRuP and LaRu2P2 induces highly anisotropic structural changes and suppresses the superconducting transition temperatures. Undoped ZrRuP [hexagonal, a=6.445(4) Å, c=3.765(2) Å] systematically expands for ZrRuP1−xBx (x=0.05, 0.10, 0.15, 0.20, 0.40) in the a direction to 6.949(4) Å and shrinks in the c direction to 3.601(3) Å. Superconductivity is still present in the boron-substituted samples, although Tc drops from 10.1 K in ZrRuP to 5.6 K in ZrRuP0.6B0.4. LaRu2P2 [tetragonal, a=4.032(2) Å, c=10.632(7) Å] remains essentially unchanged along the a axis [a=4.037(1) Å] upon substitution at a starting composition of LaRu2P1.6B0.4, but shrinks along the c axis to 10.477(5) Å. Accordingly, the superconducting Tc drops from 4.0 K for LaRu2P2 to 2.0 K for LaRu2P1.6B0.4.