Discovery of new nitride perovskite materials by high-throughput methods

Abstract

Perovskites are an abundant and commercially-important class of materials. From oxide ceramics used in ultrasonics applications to hybrid inorganic-organic halide perovskites for photovoltaics, perovskites span constituent species and application fields. Despite their abundance and tolerance of different elemental makeup, there are very few known nitride perovskites.

This work describes the materials discovery of two entirely new nitride perovskites: CeMoN3 and CeWN3. These materials were made in thin film form using high-throughput combinatorial methods. These compounds were selected via high-throughput screening, both computational and experimental. The narrowed scope set by this screening step led to the choice to focus on the optimization of the (Ce,Mo)Nx and Ce,W)Nx systems.

The main outcome of this thesis is the addition of the nitride perovskites CeMoN3 and CeWN3 to the list of known nitride perovskites, which was done by optimizing the processing conditions of each. The oxygen-free nitride perovskite CeMoN3 was isolated from other phases using rapid thermal annealing (RTA) of films. The nitride CeWN3 was grown as a single-phase perovskite using a high temperature film growth technique.

Another outcome of this work is the identification of an often-seen competing phase as a fluorite-family phase, similar to that observed in oxide perovskites. Fluorite phases in the (Ce,Mo)Nx and (Ce,W)Nx systems have never been reported before. The addition of this information led to the hypothesis that similar to those oxide perovskites, fluorite is an intermediate phase between amorphous and perovskite. This was confirmed by annealing films for the perovskite CeMoN3, although annealing films in the (Ce,W)Nx system often resulted in W reduction.

Preliminary properties are reported for the new nitride perovskites. Magnetic property measurements indicate that CeWN3 is paramagnetic to low temperatures (2K) with short-range antiferromagnetic correlations and that CeMoN3 has an antiferromagnetic ordering temperature of ~8K.

This work highlights the effectiveness of combined computational and experimental high-throughput approaches in materials discovery efforts. The successful identification of two novel nitride perovskite phases in this work demonstrates a positive outlook for identification of new perovskite nitride phases and phase evolution information provides useful assistance for those developing them.