Treść książki

Przejdź do opcji czytnikaPrzejdź do nawigacjiPrzejdź do informacjiPrzejdź do stopki
40
2.GrowthofABO
3andBO
2Crystals
growPZTcrystalsfromallconcentrationrange,includingthemorphotropic
boundaryregion.Unfortunately,thequalityofas-grownsamplesisnotvery
goodinmostcases,andPZTcrystalscompositionisnotuniform[36,37].
Bulkrutilecrystalscanbealsoobtainedduetochemicaltransport
inclosedsystems.Forexample,telluriumtetrachloridewasusedasatrans-
portagentunderconditionsofreversiblechemicalreactioncontrolledby
propertemperaturedistributionindissolutionandcrystallizationzones
ofTiO
2[38].
Althoughadetaileddiscussionofthincrystallinefilmsfabricationisnot
thesubjectofthischapter,itshouldbeunderlinedthatsophisticatedtech-
niques,allowingcontrolledcrystallizationevenontheatomicscale,and
thereforeenablingtheformationofcomplicatedmulti-componentstruc-
tureshavingdesirablephysicalproperties,arenowavailable.Themostuse-
fulofthesetechniquesareMolecularBeamEpitaxy(MBE)[39,40],Metal-
-OrganicChemicalVapourDeposition(MOCVD)[41,42],AtomicLayer
Deposition(ALD)[43,44],sputtering[45],sol-gel[46]andPulsed
LaserDeposition[47-49].
2.4.TypicalMethodsforEvaluationofQuality
ofOxideCrystals
Themostimportantmethodsforthedeterminationofcrystalqualityin-
cludethedifractionmethods,microscopicmethods,andthermalanalysis.
Difractionmethodsarebasedontheinterferenceofwavesscatteredbyat-
omsofacrystalstudiedandprovidefullinformationonthestructureofele-
mentarycells.Analysisofelasticwavescatteringbringsinformationonthe
staticstructureofmatter.Thedifractionmethodsemploythefactthatfor
smallwavelengthsthecrystalstructureisathree-dimensionaldifraction
gratingandthewavesarescatteredonlyincertaindefineddirections.There
aretwomainmethods:X-raydifractionandneutrondifraction.Inthe
X-raydifractionofsinglecrystals,onthebasisofthespatialdistribution
ofscatteredX-raysandtheirintensities,itispossibletoobtainaccurateval-
uesofelementarycellparametersanditssymmetry,usingBragg’slawor
Laueconditions[50-52].AccordingtotheBragg’slawtheX-raysreflected
fromparticularcrystallographicplanesundergoconstructiveinterference
ifthediferenceintheopticalpathwaysoftheraysreflectedfromafamily
ofplanesisequaltonλ:
(2.14)