Rapid cooling for avoiding the recombination of Zn vapor and O-2 derived from the solar thermal dissociation of ZnO is investigated using a thermogravimeter coupled to a quenching apparatus. The ZnO sample, which is placed in a cavity receiver and directly exposed to concentrated solar irradiation, underwent dissociation in the temperature range 1,820-2,050 K at a rate monitored by on-line thermogravimetry. The product gases were quenched by water-cooled surfaces and by injection of cold Ar at cooling rates from 20,000 to 120,000 K/s, suppressing the formation of ZnO in the gas phase and at the walls. Zinc content of the collected particles downstream varied in the range 40-94% for Ar/Zn(g) dilutions of 170 to 1,500.