ii ABSTRACTSOF PAPERSTO APPEAR IN J. PHYS. CHEM. SOLIDS Vol.8, No. 10

a localizationof conductionelectronsto the Al electrical resistivitiesof sampleswith severaland Sn atoms.The valuesof He~i are consistent valuesof x. For x ~ 0.06, eachsampleshowedwith the RKKY theory for spin-densityoscillations, two Zeemanpatternsin the Mössbauerspectra

which are attributed to tetrahedralandoctahedralReceived24 November1969 cationsrespectively.The spectrumdue toRevised16 ,~1arch1970 octahedralcationsappearedto be compositeand

an explanationis given.Whenx ~ 0.8, thespectrashowedonly quadrupolesplitting. From

4. AN X-RAY AND NEUTRON theseobservations,it appearsthat fast electronDIFFRACTION STUDY ON A PHASE hoppingoccurs amongoctahedralsitesforTRANSITION IN THE U409 PHASE x ~ 0.6. This conclusion,togetherwith the

TamotsuIshii, Keiji Naito, Keichi variation of conductivitywith x, suggeststhatOshima,Departmentof NuclearEngineering, the systemis metallic in type in the rangeFaculty of Engineering,University of 0 ~ x ~ 0.6, andn-type semiconductingin theTokyo, Bunkyo-ku, Tokyo, Japanand range 0.8 ~ x ~ 1.0.YoshikazuHamaguchi,PhysicsDivision,

Received6 February 1970JapanAtomic EnergyResearchInstitute,Tokai, Ibaraki, Japan

6. INITIAL AND DISCHARGE TIME-A neutronandX-ray diffraction studywas DEPENDENTCONDUCTIVITY IN

madeon the phasetransitionof 1340~and ALKALI HALIDE SINGLE CRYSTALSU4O9...~which occurs at a region slightly above L.B. Harris, School of Physics,Universityroom temperature.On the basis of the neutron of N.S.W., Kensington,N.S.W. 2033,dataof the fluorite type reflections,and the AustraliaX-ray diffraction dataof the superlatticelines,the behaviourof oxygen atomsduring thetransitionis discussed.In U 409~, the vacancies Initial transientconductivity as,. and dischargein the fluorite oxygen sites increaseat the conductivity ~d measuredin KBr and NaC1 singletransitionwhen it is approachedfrom low- crystalsfrom 50 to 200°Cis explainedin termstemperatureside. Above the transition tempera- of chargetransportandchargeblocking withoutture some portionsof the lattice oxygen atoms any needto postulatedipole relaxation. Experi-leave the lattice sitesand enterinto the inter- ment determinesa low-temperatureathermalstitial positions.Theseinterstitial oxygen atoms linear transient,which fits a simpleexhaustioncontributeto intensify the superlatticelines, processof chargeflow into traps,anda higher-

temperaturethermalnon-lineartransientwhichReceived7 July 1969 correlateswith the cation-vacancyflow of normal

Revised6 April 1970 conduction.The low-temperaturetrapsareidentified with sites in the dislocationsub-

structure,whilst transientconductivity at higher

5. MOSSBAUER STUDIES OF THE temperaturesresults from a patternof inhomo-CHARGE TRANSFERPROCESSIN geneouschargetransportdeterminedby theTHE SYSTEM Zna,Fe3_xO4 physicalsubstructure.Direct evidenceforD.C. Dobson, J.W. Linnett and M.M. inhomogeneousspacechargeis providedby the

anomalousreversalof chargeflow in certainRahman,Departmentof PhysicalChemistry,University of Cambridge, dischargetransients.England

Received17 December1969Revised30 March 1970

The ferrite systemZn~Fe3_2O4wasinvesti-gatedby taking Mössbauerspectraandmeasuring