We report on ZnO-based thin-film transistors (TFTs) employing lanthanum aluminate gate dielectrics (LaxAl1-xOy) grown by spray pyrolysis in ambient atmosphere at 440 C. The structural, electronic, optical, morphological, and electrical properties of the LaxAl1-xOy films and devices as a function ofthe lanthanum to aluminium atomic ratio were investigated using a wide range of characterization techniques such as UV-visible absorption spectroscopy, impedance spectroscopy, spectroscopic ellipsometry, atomic force microscopy, x-ray diffraction, and field-effect measurements. As deposited LaAlOy dielectrics exhibit a wide band gap (6.18eV), high dielectric constant (k~16),low roughness (1.9 nm), and very low leakage currents (<3nA/cm2). TFTs employing solution processed LaAlOy gate dielectrics and ZnO semiconducting channels exhibit excellent electron transport characteristics with hysteresis-free operation, low operation voltages (10 V), high on/off current modulation ratio of >106, subthreshold swing of 650 mV dec-11, and electron mobility of 12 cm2 V-1 s-1.