Other types of disorder Solid state ionics

1 other types of disorder

1.1 ionic glasses
1.2 polymer electrolytes
1.3 nanostructures

other types of disorder
ionic glasses

the studies of crystalline ionic conductors excess ions provided point defect continued though 1950s, , specific mechanism of conduction established each compound depending on ionic structure. emergence of glassy , polymeric electrolytes in late 1970s provided new ionic conduction mechanisms. relatively wide range of conductivites attained in glasses, wherein mobile ions dynamically decoupled matrix. found conductivity increased doping glass salts, or using glass mixture. conductivity values high 0.03 s/cm @ room temperature, activation energies low 20 kj/mol. compared crystals, glasses have isotropic properties, continuously tunable composition , workability; lack detrimental grain boundaries , can molded shape, understanding ionic transport complicated lack of long-range order.

historically, evidence ionic conductivity provided in 1880s, when german scientists noticed well-calibrated thermometer made of thuringian glass show −0.5 °c instead of 0 °c when placed in ice shortly after immersion in boiling water, , recover after several months. in 1883, reduced effect 10 times replacing mixture of sodium , potassium in glass either sodium or potassium. finding helped otto schott develop first accurate lithium-based thermometer. more systematic studies on ionic conductivity in glass appeared in 1884, received broad attention century later. several universal laws have been empirically formulated ionic glasses , extended other ionic conductors, such frequency dependence of electrical conductivity σ(ν) – σ(0) ~ ν, exponent p depends on material, not on temperature, @ least below ~100 k. behavior fingerprint of activated hopping conduction among nearby sites.

polymer electrolytes

in 1975, peter v. wright, polymer chemist sheffield (uk), produced first polymer electrolyte, contained sodium , potassium salts in polyethylene oxide (peo) matrix. later type of polymer electrolytes, polyelectrolyte, put forward, ions moved through electrically charged, rather neutral, polymer matrix. polymer electrolytes showed lower conductivities glasses, cheaper, more flexible , easier machined , shaped various forms. while ionic glasses typically operated below, polymer conductors typically heated above glass transition temperatures. consequently, both electric field , mechanical deformation decay on similar time scale in polymers, not in glasses. between 1983 , 2001 believed amorphous fraction responsible ionic conductivity, i.e., (nearly) complete structural disorder essential fast ionic transport in polymers. however, number of crystalline polymers have been described in 2001 , later ionic conductivity high 0.01 s/cm 30 °c , activation energy of 0.24 ev.

nanostructures

in 1970s–80s, realized nanosized systems may affect ionic conductivity, opening new field of nanoionics. in 1973, reported ionic conductivity of lithium iodide (lii) crystals increased 50 times adding fine powder of ‘’insulating’’ material (alumina). effect reproduced in 1980s in ag- , tl-halides doped alumina nanoparticles. similarly, addition of insulating nanoparticles helped increase conductivity of ionic polymers. these unexpected results explained charge separation @ matrix-nanoparticle interface provided additional conductive channels matrix, , small size of filler particles required increase area of interface. similar charge-separation effects observed grain boundaries in crystalline ionic conductors.