(1977-01) Western, Arthur B.; Baker, A. G.; Pollina, R. J.; Schmidt, V. Hugo
The proposed tricritical point in KDP occurs if the critical field, Ecr, can be brought to zero by applying pressure. The Landau equation of state E = A0(T - T0)P + BP3 + CP5 gives straight-line “isopols” in the T-E plane. We obtain values for A0, B and C and thus Ecr by observing such isopols. We find A0 = 4.3 × 10-3; B = -2.35 × 10-11 C = 5.91 × 10-19 cgs esu for the crystal studied at ambient pressure. These values lead to Ecr = 232 V/cm and δPspon (Tc) = 1.82 C/cm2. High pressure results are imminent.
(1978-01) Schmidt, V. Hugo; Western, Arthur B.; Baker, A. G.; Bacon, Charles R.
Static dielectric results for a KH2PO4 crystal at pressures of 0, 2, and 2. 4 kbar are analyzed in terms of a Landau free energy expansion using the “isopol” technique. The measured exponent δ at 2. 4 kbar is consistent with the mean-field tricritical value of 5. This result and the Landau parameter values indicate a tricritical point near 2. 4 kbar.
