One-shot wet chemical synthesis and physical properties of pyrochlore iridates A2Ir2O7, (A = Sm, Gd, Dy and Er)

Abstract

Iridates of the pyrochlore A2Ir2O7 family are interesting materials whose low-temperature properties depend sensitively on the A/Ir ratio. Due to specific difficulties, namely: (i) the volatile nature of IrO2 above 1323 K, and (ii) slow reaction kinetics between IrO2 and A2O3 below 1323 K (where A is a members of the lanthanide series), it is challenging to prepare phase pure and stoichiometric A2Ir2O7 samples using the conventional solid state reaction (SSR) method in a reasonably short time. To overcome these limitations, we synthesized A2Ir2O7 with A = Sm, Gd, Dy, and Er using a wet chemical reaction (WCR) method in a single sintering step at T = 1273 K (a temperature well below the sublimation point of IrO2) for 12 h, and compared their electrical resistivity, magnetic susceptibility and specific heat with the SSR samples. We show that WCR samples exhibit metal-to-insulator & all-in all-out transitions in agreement with previous reports. The high density, low-sintering temperature, lack of IrO2 losses, and shorter preparation time are some of the attractive features of WCR method. This should be useful in exploring the true ground state properties of these materials in future.