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The zeta potential-pH and yield stress-pH behaviour of washed spherical α-Al₂O₃ suspensions with and without adsorbed multilayer polyelectrolytes up to 4 layers of poly(styrene sulphonic acid) sodium salt or PSSNa (100 kDa) and polyethyleneimine or PEI (70 kDa) adsorbed sequentially were characterised. The maximum yield stress (τ_ymax) of washed spherical α-Al₂O₃ is 81.8 Pa located at pH_ξ=0 at ~9.2. Particles with the first layer (layer 1) of PSSNa displayed negative zeta potential over the whole pH range of 3 to 8. Particles containing 3 layers with layer 3 being PSSNa also displayed negative zeta potential over the same pH range. The magnitude of the Layer 3 PSSNa is smaller. Similarly, the zeta potential remained positive for layer 2 and layer 4 PEI over the whole pH range of 3 to 8. At the dosage of 0.5 dwb% PSSNa and 0.1 dwb% PEI, monolayer coverage of PSSNa for layer 1 and 3 and of PEI for …