The high temperature preparation and property measurements of CaTaN2: A ternary superconducting nitride

Highly crystalline CaTaN2 was prepared by the reaction of Ca(NH2)2 and Ta3N5 in a specially designed reaction vessel at high temperatures (> 1300 °C). Even when reaction conditions varied considerably, the samples were always contaminated by small amounts of Ca2TaN3, TaN, or TaN0.1. SQUID measurements obtained on a sample contaminated by Ca2TaN3 and a sample contaminated by TaN and TaN0.1 showed superconducting transitions at 9.6 K and 9.1K, respectively. Resistivity measurements carried out on a sintered pellet of CaTaN2 contaminated by TaN0.1 showed a ρ(300K) = 0.0147 ω cm and weakly rising resistivity with lower temperatures, likely due to the random alignment of the polycrystalline grains.