Sintering and properties of lead-free (K,Na,Li)(Nb,Ta,Sb)O3 ceramics

Two different stoichiometric (K0.44Na0.52Li0.04)(Nb0.86Ta0.Sb-10(0.04))O-3 and non-stoichiometric (K0.38Na0.52Li0.04)(Nb0.86Ta0.10Sb0.04) O-2.97 compositions were prepared by the conventional mixed oxide and carbonate route. Low temperature synthesis process at 700 degrees C for 2 h. and further attrition milling process resulted in agglomerated powder of 500nm of primary particles in the range of 50-70nm. The ceramics sintered at 1125 degrees C showed the highest densification that decreased for higher sintering temperatures. Non-stoichiometric composition densification process was assisted through the presence of a liquid phase that promotes grain growth and the appearance of a secondary ferroelectric phase with tungsten-bronze type structure. The samples showed a relaxor type behaviour that diminished because of the compositional homogeneity improvement of the liquid phase in the non-stoichiometric samples. The higher piezoelectric properties were obtained for the samples with high ferroelectric type dielectric constant versus temperature behaviour. In the non-stoichiometric samples piezoelectric constant d(33) values reach similar to 200pC/N. (c) 2007 Elsevier Ltd. All rights reserved.