3. Explain the following experimental observations: (a) TiO can be used as an efficient electrical gas sensor for wide concentrations of O2 whereas NiO is not as effective for this application. (5 marks) (b) Manganese(II) oxide cannot be poled in a magnetic (M) field. (5 marks) (c) The Curie temperature (Tc) of a barium titanate thermistor can be adjusted by doping with strontium cations at the A site in the crystal lattice. (5 marks) (d) The addition of few-layer graphene into the grain boundaries of strontium titanate thermoelectric ceramics improves the thermoelectric figure of merit (ZT) for these materials compared to strontium titanate ceramics with no graphene added