Substrate, liquid crystal antenna and high-frequency device

A substrate, comprising:

• SiO2;
• Al2O3;
• B2O3;
• alkali metal oxides including Na2O and K2O;
• and
• alkaline-earth metal oxides including MgO, CaO, and SrO,
• wherein the SiO2 is a main component in a mole percentage on an oxide basis,
• a total amount of the Al2O3 and the B2O3 is in a range of more than 3 to 24%,
• the substrate has a content molar ratio of {Al2O3/(Al2O3+B2O3)} in a range of 0.01 to 0.45,
• a content molar ratio of {Na2O/(Na2O+K2O)} in a range of 0.01 to 0.99,
• an amount of the Al2O3+1% is equal to or greater than 4% and is less than a total amount of the MgO, the CaO, and the SrO,
• a content of the MgO is 3% or higher,
• a total amount of the alkaline-earth metal oxides is in a range of 5 to 13%,
• and the substrate has a relative permittivity (a) as measured at 20° C. and 10 GHz of 4 or more and 10 or less,
• a relative permittivity (b) as measured at 20° C. and 35 GHz of 4 or more and 10 or less, and
• a ratio represented by [a relative permittivity (c) as measured at an arbitrary temperature in a range of −40 to 150° C. and at 10 GHz]/[the relative permittivity (a)] of 0.993-1.007.