Maximising ZT is a complex task due to the interconnected nature of its components. A high Seebeck coefficient is achieved by flat, non-disperse electronic bands with large charge-carrier effective masses. Conversely, a high electrical conductivity requires high charge-carrier mobility and relatively disperse band edges. At the same time, high electrical conductivity leads to high electronic thermal conductivity (κ e ∝ σT ). Lattice thermal conductivity is often the limiting factor in candidates that could otherwise challenge the current best-performing thermoelectric materials. Ideally TE materials would show the low thermal conductivity characteristic of an amorphous material (glass) and the high electrical conductivity of a crystal -a "phonon-glass, electron-crystal" material. In recent years the focus has been on transitioning from traditional thermoelectric materials such as PbTe, Bi 2 Te 3 and Bi 2 Se 3 , which contain toxic and rare elements, to materials formed from more abundant and environmentally-friendly components. In theory, oxides are a good fit for thermoelectric applications given their high-temperature stability in air, low toxicity and straightforward synthesis paths. Indeed, several p-type oxides with ZT exceeding unity have been discovered since 1997, when NaCo 2 O 4 showed promise as an oxide thermoelectric. Na x CoO 2 and Ca 3 Co 4 O 9 are currently some of the best ternary p-type thermoelectrics, with ZT exceeding 1 at 800 K and 1.1 at 1000 K, respectively. Mixed-anion materials have also proven to be successful, with p-type oxide BiCuOSe exhibiting a high ZT of 1.4 at 923 K. Recently, two oxypnictogens LaZnOP and LaZnOAs were predicted to have theoretical maximum p-type ZT scores of 2.10 and 1.92, respectively, at 2