NOVELTY - Ceramic spray suspension (S1) comprises a minority terpineol-based solvent; a majority organic solvent having a vapor pressure higher than the vapor pressure of terpineol; an organic binder; a dispersant; and a powdered ceramic composition selected from an electrolyte material and an electrode material.    USE - As ceramic spray suspension used in the fabrication of electrochemical systems e.g. solid oxide fuel cells, solid oxide electrolysers, ceramic oxygen generation systems or ceramic membrane reactors.    ADVANTAGE - The spray suspension allows aerosol deposition of green ceramic layers that can be sintered to produce both dense and porous ceramic layers. The suspensions and deposition approach allow formation of thin layers of varying microstructure and composition in the sintered state. The ceramic suspension is well-suited to coating porous or dense layers. The system has high viscosity and solids loading, which allows the films to bridge pores in porous substrates effectively. The system also has wetting behavior that allows effective coating of dense substrates. Electrolytes applied by spray coating may be co-sintered at the same time as their electrode supports, which reduces production cost. Spray coating also allows sequential spray deposition of multiple layers of ceramic materials having composition, which may then be fired together to achieve simultaneous densification. The ability to deposit at least two functional layers or layer thicknesses within a single firing cycle reduces manufacturing cost.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for:    (a) a method (M1) of coating a porous substrate involving forming a porous substrate; applying a coating of (S1) to the substrate; applying a second coating of (S1) to the coated substrate; and co-sintering the coated substrate;    (b) making (M2) an electrochemical cell involving providing a porous electrode; applying coating to the electrode according to method (M1); applying a coating of a third ceramic suspension comprising an electrode interlayer material having a polarity opposite the polarity of the porous electrode; applying a coating of a fourth ceramic suspension to the electrode interlayer-coated electrode comprising a current-carrying electrode material having a polarity opposite the polarity of the porous electrode; and co-sintering the coated electrode.