Piezoelectric single crystals with the ordered langasite structure A 3BC3D2O14 including Sr 3TaGa3Si2O14Sr3NbGa 3Si2O14 Ca3TaGa3Si 2O14 and Ca3TaAl3Si 2O14 (CTAS), were studied as a function of temperature, up to 900 °C. The dielectric permittivity ε11 and piezoelectric coefficient d11 of the ordered crystals were found to be on the orders of 12-16 and 4-5 pC/N, respectively, slightly lower than langasite (La3Ga5SiO14-LGS) or langanite (La3 Ga5.5Nb00.5O14) crystals which possess a disordered structure. The mechanical quality factor Q and electrical resistivity ρ, however, were found to be greatly improved at elevated temperatures 500 °C, being one to two orders of magnitude higher, due to cation ordering. Of particular interest is the CTAS crystal, in which, the Ga cations are totally replaced by low cost Al cations. Together with its thermally stable piezoelectric properties and high electrical resistivity, CTAS crystals offer a competitive material for high temperature sensing applications. © 2009 American Institute of Physics.