Single crystals of phosphoric acid (H3PO4) doped triglycine sulfate (TGSP) are grown from aqueous solution containing 10-50 mol% of H3PO4. Large sized crystals of dimension (70 turn x 40 mm x 25 mm) suitable for IR detector applications are obtained with 20 mol % of H3PO4. They exhibit elongated domains, and the domain density is higher than in undoped TGS crystals. FT-IR analysis indicates the presence of both zwitter and glycinium ions in the doped TGSP crystals, which is, due to the low incorporation of H3PO4 into the TGS crystal lattice. The dielectric properties TGSP crystals measured in the temperature range 27-65degreesC and in frequency range 102-105 Hz show a broad transition, and the peak dielectric constant values are reduced with increasing H3PO4 concentration. Hysteresis loops with high coercive fields are observed up to 20 mol % of H3PO4. At a higher concentration, double loops are observed due to the polarization switching inhibition by H3PO4 molecules. Dopant concentration is found to have a marginal influence on the spontaneous polarization of the TGSP crystals. (C) 2003 Elsevier B.V. All rights reserved.