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微波介质陶瓷.pdf

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PLYSICALREVIE%'VOLUME1~9,NUMBER41SFEBRUARY1963 TemyeratureDeyendenceofDielectricConstantsofCubicIonicComyounds A.J.BoslKANAiNDE.E.HAvINGA I'hilipsResearchLaboratories,X.V.I'hilips'GloeilamPenfabriekenBindhoeen-Vetherlands (Received19September1962) Thetemperatureandpressuredependenceofthedielectricconstantofanumberofcubichalidesand oxideswithabroadrangeofdielectricconstantshavebeendetermined.Forlow-~compoundsthedielectric constantincreaseswithincreasingtemperature,whereasforhigh-ecompoundsthedielectricconstantde- creaseswithincreasingtemperature.Hydrostaticpressurelowersthevalueofthedielectricconstantfor allcompoundsmeasured.l.orferroelectricsandantiferroelectricsarelationhasbeenfoundbetweenthe CurietemperatureandtheCurieconstant.Threeeffectscontributetothetemperaturedependenceofa dielectricconstant:thedecreaseinthenumberofpolarizableparticlesperunitvolumeasthetemperature increases,whichisadirectresultofthevolumeexpansion(A),theincreaseofthemacroscopicpolarizability duetothevolumeexpansion(8),andthetemperaturedependenceofthemacroscopicpolarizabilityatcon- stantvolume(C).Theexperimentaldatahavebeenusedtocalculatethesedifferentcontributions.Itis foundthatthevolume-dependentcontribution(A+8)isalwayspositiveandthatthedirecttemperature contribution(C)canbeeitherpositiveornegative.Whereopticaldatawereavailableinliteraturetheywere usedtocalculatethecontributionsoftheopticalandinfraredpartsofthepolarizabilitytothetemperature andvolumedependenceofthepolarizability.Theresultsarediscussedwiththeuseofaclassicalionic model. I.INTRODUCTIONinAuencesaffectitsmagnitude.Itcan,namely,beshown ' Napreviouspaper'ithasbeenshownthatthreethattheinternalQeldsduetothenon-cubicenviron- -~effectscontributetothetemperaturedependenceofmentsmakethemselvesnoticeableonlyoverrather thedielectricconstanteofacubicorisotropicmaterial.shortdistances.Intheperovskitestructure,forexample, ForsuchamaterialthemacroscopicClausius-3Tossottithemaincontributiontothesefieldsarisesfromthe formula1)olds:nearestne