Effect of Calcination Conditions and Excess Alkali Carbonate on the Phase Formation and Particle Morphology of Na0.5K0.5NbO3 Powders

Sodium‐potassium niobate [Na0.5K0.5NbO3] powders were prepared following the conventional mixed oxide method. An orthorhombic XRD pattern, consistent with single‐phase Na0.5K0.5NbO3, was obtained after calcination at 900°C for 6 h. Introducing 5 mol% excess Na2CO3 and K2CO3 into the starting mixture allowed milder calcination conditions to be used, for example 800°C for 2 h. Primary particles in 5 mol% excess samples were cuboid, with maximum sizes of ∼2.5 μm. Equiaxed 0.3–0.4‐μm particles were formed for non‐excess powders, and also for powders prepared with 1 and 3 mol% excess alkali carbonates. The results suggest liquid formation during calcination of the excess 5‐mol% starting powders.