Effect of pressure on ionic conductivity in rubidium silver iodide and silver iodide

The effect of pressure on the ionic conductivity of RbAg4I5 and AgI has been measured, using single crystals and polycrystalline samples, up to pressures of 6 kbar. The activation volumes for motion in cr-RbAg4I5 and B-RbAgI5, respectively, are -0.4 ±.2 cm3/mole and -0.2 ±.l cm3/mole. In 4a-AgI, the motion volume increases from 0.56 ±.l cm3 /mole at 435 K to 0.8 ±.l cm3/mole at 623 K. These values are unusually small in relation to the activation energies and are not consistent with the strain energy model or a domain diffusion mechanism. The negative activation volume for super-ionic RbAgIand the small size of the activation volume for cr-AgI may be 4S the result of pressure increasing the interaction enthalpy between the diffusing ions. The logarithms of the ionic conductivities of cr-and B-RbAgIin4S crease linearly at first and then decrease quadratically with pressure. This is related to the large quadratic pressure dependence of the second-order transition temperature, 6T (K) = 0.14lP (kbar) + 0.111p2 (kbar2). c The variation of the 122 K transition temperature with pressure is 6T(K) = S.6SP (kbar) -0.S3P2 (kbar2), implying a molar volume change of c VB -Vy = 0.37 ±.Ol cm3 /mole and a change in compressibility KB -Ky = 0.033 ±.OOI x 10-11 cm2/dyne, across the transition. The ionic conductivity of y-RbAg Iinitially decreases with an 4S activation volume of 9 ±l cm3/mole, and then levels off with increasing pressure. This may be the result of an extrinsic-like region or of grain-boundary conduction. The negative activation volume for conduction along the c-axis in B-AgI has been confirmed. Both low-temperature phases have large formation volumes consistent with the theory of Rice et al. of transitions to the superionic phase.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Physics

Year dc:date

2011

Author dc:creator

• Allen, Paul Clement

Contributors dc:contributor

• Lazarus, David

• ionic conductivity
• rubidium silver iodide
• silver iodide
• single crystals
• polycrystalline

Statement dc:rights

• 1977 Paul Clement Allen

Language dc:language

en

Identifier

252664

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/25625