200 g ZnMoO4 single crystals, both pure and doped with WO3, were grown from appropriate powder mixtures of oxides via the lowerature gradient Czochralski technique, and plates cut from them were characterized in detail. The crystal-chemical formulas of non-stoichiometric Zn1.010ZnyMo1-yO1.010+3-2y (y = 0.007) crystals, being substitutional solid solutions with ionic defects, such as ZnMo4-, VO2+, and Zni2′, were established based on determination of the compositions, densities and lattice unit cell parameters with very high accuracy. This characterization allowed for clarification of the role played by each stage of crystal growth, including solid-phase powder synthesis, higherature homogenization and crystallization, which proceeded sequentially in one reactor that was semi-open to the air. It was shown that MoO3 volatility is the primary source of issues. The first stage, resulting in a non-equilibrium grain-zoning product, was the key to creating MoO3 vapor pressure in the reactor and a melt composition enriched by the ZnO component. The conditions for the stable crystallization of nonstoichiometric crystals were determined. The experimentally observed shifts in the characteristic liquidus and solidus temperatures of non-stoichiometric ZnMoO4 crystals doped by WO3 were found to be of importance to minimize the negative effects of peritectic melting.