Heating of a ceramic green body is a key step in sintering. We have created inside a spark plasma sintering apparatus pressure-less sintering conditions that allow homogeneous and extremely rapid heating. Dense and crack-free zirconia ceramic was sintered at heating rates of up to 500 degrees C min(-1) and dwell times of 2 min. This extremely fast sintering process is accompanied by extremely rapid grain growth, indicating a non classical sintering mechanism. No grain size gradients were observed inside the sintered zirconia ceramics.