We have studied the influence of cryochemical and ultrasonic processing on the formation, structure, particle size, and thermal decomposition of xerogels in the ZrO2〈Y2O3〉–Al2O3 (20 wt %) system. Nanopowders of tetragonal-zirconia-based solid solutions with a high degree of tetragonality (c/a = 1.4366) have been synthesized. Al2O3 has been shown to slow down t-ZrO2 crystallite growth in the temperature range 600–1400°C. We have optimized nanopowder consolidation conditions, obtained nanoceramics stable to low-temperature “aging” in a humid medium, and investigated their physicochemical and mechanical properties.