In the present work sintering and characterisation of lead free ceramic materials based on potassium sodium niobate (KNN) has been studied. Ceramics with the composition (K0.5Na0.5)(Nb1-xSbx)O3 (x=0÷0.10) and (1-x)(K0.5Na0.5)Nb1-ySbyO3-xBaTiO3 (x=0.02, 0.04; y=0.04, 0.07) were prepared by conventional ceramic processing technology. MnO2 of 0.5 mol% was added to improve the sintering and densification of ceramics. X-ray diffraction analysis confirmed that obtained samples had a pure perovskite structure with no evidence of secondary phase. The co-effects of MnO2 doping and Sb5+ substitution for Nb5+ at perovskite B-site lead to notable improvement in the dielectric permittivity if compared with pure KNN.