INVESTIGATIONS ON THE EXISTENCE OF A HIGH-TEMPERATURE PHASE-TRANSITION IN AMMONIUM-SULFATE CRYSTALS

The existence of a high-temperature phase transition in ammonium sulph ate (AS) crystals is discussed. The DC electrical conductivity and the dielectric permittivity in the temperature range K are measured and t he results are examined trying to detect the proposed phase transition . The results indicate no evidence for a ferroelectric phase transitio n, but the anomaly observed at 423 K simply is the result of variation s in the conduction mechanism which could be attributed to an order-di sorder type of phase transition.