Ba(5)LnZnTa(9)O(30) (Ln = La, Sm) ceramics were prepared by high temperature solid-state reaction route. The samples were characterized by X-ray diffraction, scanning electron microscopy (SEM), and differential scanning calorimetry (DSC) methods. They belong to paraelectric phase of filled tetragonal TB structure at room temperature with unit cell a = 12.5909(4) Angstrom, c = 3.9622(2) Angstrom for Ba5LaZnTa9O30; and a = 12.5777(4) Angstrom, c = 3.9544(2) Angstrom for Ba5SmZnTa9O30. At 1 MHz, Ba5LaZnTa9O30 has high dielectric constants of 89 with low dielectric loss 0.0067, and temperature coefficients of the dielectric constant (tau(epsilon)) - 811 ppm degreesC(-1); Ba5LaZnTa9O30 has dielectric constants of 74 with low dielectric loss 0.0035, and tau(epsilon) -474 ppm degreesC(-1). (C) 2004 Elsevier Ltd. All rights reserved.