AbstractThe temperature dependence of NQR frequencies of halogens in ammonium hexahalotellurates(IV) has been reinvestigated in a wide range of temperature. A second‐order phase transition was definitely located at 89 K for (NH4)2TeCl6,below which temperature the existence of multiplet structure was suggested The temperature of a first‐order phase transition was determined for (NH4)2TeBr6at 194 K in addition to the phase transition previously reported, which was located accurately at 212 K. The lowest‐frequency line among the three81Br resonance lines observed below 194 K exhibited a positive temperature coefficient whereas the remaining two lines showed normal negative temperature coefficients. Except for the highest‐frequencyv1andv2lines, the all four127I lines observed for (NH4)2TeI6showed anomalous temperature dependences. These temperature dependences could be interpreted by considering that the Te‐I…H type hydrogen bonds partially break due to the thermal activation of the motion of ammonium ions in crystals. A phase transition was located at 449 K by means of differential therm