Ferroelectrics yog Lub tswv yim, txhais, cov khoom thiab daim ntawv thov

2024 Tus sau: Angel Austin | [email protected]. Kawg hloov kho: 2024-01-15 17:25

Ferroelectrics yog cov ntsiab lus nrog spontaneous electric polarization (SEP). Cov pib ntawm nws qhov kev thim rov qab tuaj yeem yog daim ntawv thov ntawm hluav taws xob ntau E nrog qhov tsim nyog thiab cov vectors coj. Cov txheej txheem no hu ua repolarization. Nws yuav tsum tau nrog hysteresis.

Cov yam ntxwv zoo ib yam

Ferroelectrics yog cov khoom uas muaj:

1. Kev tso cai tso cai.
2. Powerful piezo module.
3. Loop.

Kev siv cov ferroelectrics yog nqa tawm hauv ntau qhov kev lag luam. Nov yog qee qhov piv txwv:

1. Radio engineering.
2. Quantum electronics.
3. ntsuas tshuab.
4. Electric acoustics.

Ferroelectrics yog cov khoom uas tsis yog hlau. Lawv txoj kev kawm tau zoo tshaj plaws thaum lawv lub xeev yog ib qho siv lead ua.

Zaj meej meej

Tsuas muaj peb yam ntawm no:

1. Reversible polarization.
2. Nonlinearity.
3. Tus yam ntxwv tsis zoo.

Ntau lub ferroelectrics tsis ua ferroelectric thaum lawv nyob hauvkub hloov tej yam kev mob. Cov kev txwv no hu ua T_K. Cov khoom coj txawv txawv. Lawv cov dielectric tas li txhim kho sai thiab nce mus txog qib khoom.

Kev faib tawm

Nws nyuaj heev. Feem ntau nws cov ntsiab lus tseem ceeb yog kev tsim cov ntsiab lus thiab cov thev naus laus zis ntawm kev tsim SEP nyob rau hauv kev sib cuag nrog nws thaum lub sij hawm hloov ntawm theem. Ntawm no muaj kev faib ua ob hom:

1. Muaj kev sib tw. Lawv cov ions hloov pauv thaum lub sijhawm txav mus los.
2. Order is chaos. Raws li cov xwm txheej zoo sib xws, cov dipoles ntawm theem pib raug txiav txim hauv lawv.

Cov hom no kuj muaj subspecies. Piv txwv li, cov khoom tsis ncaj ncees poob rau hauv ob pawg: perovskites thiab pseudo-ilmenites.

hom thib ob muaj faib ua peb chav:

1. Potassium dihydrogen phosphates (KDR) thiab alkali hlau (xws li KH₂AsO₄ thiab KH _{2 PO}4_).
2. Triglycine sulfates (THS): (NH₂CH₂COOH₃) × H ₂SO_4.
3. Ua kua siv lead ua khoom

Perovskites

Cov ntsiab lus no muaj nyob hauv ob hom:

Monocrystalline.

Lawv muaj cov pa oxygen octahedron, uas muaj Ti ion nrog lub valence ntawm 4-5.

Thaum lub sijhawm paraelectric tshwm sim, cov muaju tau txais cov qauv cubic. Ions zoo li Ba thiab Cd yog concentrated nyob rau sab saum toj. Thiab lawv cov pa oxygen yog nyob rau hauv nruab nrab ntawm lub ntsej muag. Qhov no yog li cas nws yog tsimoctahedron.

Thaum titanium ions hloov ntawm no, SEP ua tiav. Xws li ferroelectrics tuaj yeem tsim cov khoom sib xyaw nrog kev tsim cov qauv zoo sib xws. Piv txwv li, PbTiO₃-PbZrO₃ . Qhov no ua rau cov ceramics uas tsim nyog rau cov khoom siv xws li varicondas, piezo actuators, posistors, thiab lwm yam.

Pseudo-ilmenites

Lawv txawv ntawm rhombohedral teeb tsa. Lawv qhov tshwj xeeb ci ntsa iab yog qhov ntsuas kub Curie siab.

Lawv kuj yog cov muaju. Raws li txoj cai, lawv yog siv nyob rau hauv acoustic mechanisms nyob rau sab sauv loj nthwv dej. Cov khoom siv hauv qab no yog tus yam ntxwv ntawm lawv lub xub ntiag:

- resonators;

- lim nrog kab txaij;

- siab zaus acousto-optic modulators;

- pyro txais.

Lawv kuj tau nkag mus rau hauv cov khoom siv hluav taws xob thiab kho qhov muag uas tsis yog-linear.

KDR and TGS

Ferroelectrics ntawm thawj chav kawm muaj cov qauv uas npaj cov protons hauv hydrogen hu. Lub SEP tshwm sim thaum tag nrho cov protons nyob rau hauv kev txiav txim.

Cov ntsiab lus ntawm pawg no yog siv hauv cov khoom siv kho qhov muag uas tsis yog-linear thiab hauv hluav taws xob optics.

Hauv ferroelectrics ntawm qeb thib ob, protons raug txiav txim zoo ib yam, tsuas yog dipoles tsim nyob ze glycine molecules.

Cov khoom ntawm pab pawg no yog siv rau qhov tsawg. Feem ntau lawv muaj pyro receivers.

Ua kua Crystal views

Lawv yog tus yam ntxwv los ntawm lub xub ntiag ntawm cov polar molecules txheej txheem. Ntawm no, cov ntsiab lus tseem ceeb ntawm ferroelectrics tau pom meej meej.

Lawv qhov zoo ntawm qhov muag tau cuam tshuam los ntawm qhov kub thiab txias thiab vector ntawm sab nraud hluav taws xob spectrum.

Raws li cov xwm txheej no, kev siv ferroelectrics ntawm hom no yog siv rau hauv cov khoom siv kho qhov muag, saib, banners, thiab lwm yam.

Qhov sib txawv ntawm ob chav kawm

Ferroelectrics yog tsim nrog ions lossis dipoles. Lawv muaj qhov sib txawv tseem ceeb hauv lawv cov khoom. Yog li, thawj cov khoom tsis yaj nyob rau hauv dej, tab sis lawv muaj zog txhua yam muaj zog. Lawv tau yooj yim tsim nyob rau hauv polycrystal hom muab hais tias lub ceramic system yog ua.

Cov tom kawg yooj yim yaj hauv dej thiab muaj lub zog tsis txaus ntseeg. Lawv tso cai tsim ib qho crystals ntawm cov khoom tsis zoo los ntawm cov dej sib xyaws.

Domains

Txhua tus yam ntxwv ntawm ferroelectrics nyob ntawm thaj chaw. Yog li, qhov hloov pauv tam sim no muaj feem cuam tshuam nrog lawv tus cwj pwm. Lawv pom ob qho tib si hauv ib lub pob zeb thiab hauv ceramics.

Tus qauv sau ntawm ferroelectrics yog ib qho ntawm cov macroscopic qhov ntev. Nyob rau hauv nws, lub vector ntawm arbitrary polarization tsis muaj qhov sib txawv. Thiab tsuas muaj qhov sib txawv ntawm cov vector zoo sib xws hauv cov khoom nyob sib ze.

Domains cais cov phab ntsa uas tuaj yeem txav mus rau hauv qhov chaw sab hauv ntawm ib qho siv lead ua. Hauv qhov no, muaj qhov nce hauv qee qhov thiab txo qis hauv lwm qhov. Thaum muaj repolarization, cov sectors txhim kho vim yog kev hloov ntawm phab ntsa lossis cov txheej txheem zoo sib xws.

Cov khoom hluav taws xob ntawm ferroelectrics,uas yog ib leeg siv lead ua, yog tsim raws li symmetry ntawm cov siv lead ua lattice.

Cov qauv siv hluav taws xob tau txais txiaj ntsig zoo tshaj plaws yog tus cwj pwm los ntawm qhov tseeb tias thaj tsam ntawm nws yog hluav taws xob nruab nrab. Yog li, lub polarization vector yog npaj mus rau thaj tsam ntawm ib qho chaw tshwj xeeb thiab sib npaug rau nws qhov ntev. Nyob rau tib lub sij hawm, nws yog opposite nyob rau hauv kev coj mus rau lub zoo tib yam vector los ntawm sab ntawm lub ze tshaj domain.

Yog li ntawd, cov hluav taws xob tsis zoo ntawm cov thawj coj tau tsim los ntawm lub hauv paus ntawm lub taub hau-tail tswvyim. Linear qhov tseem ceeb ntawm cov thawj yog txiav txim siab. Lawv nyob 10^-4-10^-1 see

Polarization

Vim rau sab nraud hluav taws xob, lub vector ntawm hluav taws xob ua ntawm cov thawj hloov pauv. Yog li, muaj zog polarization ntawm ferroelectrics tshwm sim. Yog li ntawd, qhov dielectric tas li mus txog qhov muaj nuj nqis loj.

Lub polarization ntawm cov thawj yog piav qhia los ntawm lawv lub hauv paus chiv keeb thiab kev loj hlob vim kev hloov pauv ntawm lawv thaj tsam.

Cov qauv qhia ntawm ferroelectrics ua rau muaj kev cuam tshuam ncaj qha ntawm lawv qhov induction ntawm qib ntawm qhov hluav taws xob ntawm sab nraud. Thaum nws tsis muaj zog, kev sib raug zoo ntawm cov sectors yog linear. Ib ntu zoo li qhov txwv txwv tau hloov pauv raws li lub hauv paus ntsiab lus thim rov qab.

Nyob hauv thaj tsam ntawm thaj chaw muaj zog, cov txheej txheem zoo li no tsis tuaj yeem thim rov qab. Nyob rau tib lub sij hawm, cov sectors uas SEP vector tsim lub kaum sab xis yam tsawg kawg nkaus nrog lub teb vector loj hlob. Thiab ntawm ib qho kev nro, txhua tus thawj kab nyob raws nraim hauv thaj teb. Technical saturation tab tom tsim.

Nyob rau hauv cov xwm txheej zoo li no, thaum qhov nro txo mus rau xoom, tsis muaj qhov cuam tshuam zoo sib xws ntawm induction. Nws yogtau qhov seem D_r. Yog tias nws raug cuam tshuam los ntawm thaj chaw nrog tus nqi sib txawv, nws yuav txo qis thiab hloov nws cov vector.

Kev txhim kho tom qab ntawm kev nruj dua ua rau kev ua haujlwm zoo. Yog li, qhov dependence ntawm ferroelectric ntawm polarization reversal nyob rau hauv txawv spectra yog denoted. Ua ke nrog cov txheej txheem no, hysteresis tshwm sim.

Kev siv zog ntawm ntau yam E_r, at uas induction ua raws li tus nqi xoom, yog lub zog quab yuam.

Hysteresis txheej txheem

Nrog nws, cov ciam teb ciam teb tau hloov pauv tsis tau raws li kev cuam tshuam ntawm thaj chaw. Nws txhais tau tias muaj qhov poob ntawm dielectric vim cov nqi hluav taws xob rau kev teeb tsa ntawm cov thawj.

A hysteresis voj daim ntawv ntawm no.

Nws thaj chaw sib raug rau lub zog siv hauv ferroelectric hauv ib lub voj voog. Vim poob, lub tangent ntawm lub kaum sab xis 0, 1 yog tsim nyob rau hauv nws.

Hysteresis loops yog tsim los ntawm qhov sib txawv ntawm qhov muaj nuj nqis. Ua ke, lawv cov ncov tsim lub ntsiab polarization nkhaus.

ntsuas kev ua haujlwm

Lub dielectric qhov tsis tu ncua ntawm ferroelectrics ntawm yuav luag txhua chav sib txawv ntawm cov khoom muaj nqis txawm nyob ntawm qhov muaj nqis deb ntawm T_K.

Nws ntsuas raws li hauv qab no: ob lub electrodes yog siv rau cov siv lead ua. Nws lub peev xwm yog txiav txim siab nyob rau hauv ntau yam sib txawv.

Saum toj nontsuas T_K permeability muaj qee yam thermal dependence. Qhov no tuaj yeem xam raws li txoj cai Curie-Weiss. Cov qauv hauv qab no ua haujlwm ntawm no:

e=4pC / (T-Tc).

Nyob hauv nws, C yog Curie tas li. Hauv qab cov nqi hloov pauv, nws poob sai heev.

Tsab ntawv "e" hauv cov qauv txhais tau tias tsis yog-linearity, uas yog tam sim no nyob rau hauv ib tug nqaim spectrum nrog ib tug hloov voltage. Vim nws thiab hysteresis, qhov permeability thiab ntim ntawm ferroelectric nyob ntawm qhov kev khiav hauj lwm hom.

Type of permeability

Cov khoom siv nyob rau hauv kev ua haujlwm sib txawv ntawm cov khoom siv tsis yog-linear hloov nws qhov zoo. Cov nram qab no hom permeability yog siv los qhia lawv:

1. Statistical (e_st). Xaiv nws, siv lub ntsiab polarization nkhaus: e_st =D / (e₀E)=1 + P / (e 0_{E) » P / (e}0_E).
2. Rov qab (e_p). Qhia txog kev hloov pauv ntawm polarization ntawm ferroelectric nyob rau hauv qhov sib txawv raws li qhov sib npaug ntawm qhov chaw ruaj khov.
3. effective (e_ef). Xam los ntawm qhov tseeb tam sim no kuv (hais txog yam uas tsis yog-sinusoidal) mus ua ke nrog cov khoom tsis-linear. Nyob rau hauv cov ntaub ntawv no, muaj ib tug active voltage U thiab ib tug angular zaus w. Cov mis ua haujlwm: e_ef ~ C_ef =I / (wU).
4. pib. Nws tau txiav txim siab hauv qhov tsis muaj zog heev.

Ob hom pyroelectrics

Cov no yog ferroelectrics thiab antiferroelectrics. Lawv muajmuaj BOT sectors - domains.

Nyob rau hauv thawj daim ntawv, ib tug sau ua ib tug depolarizing sphere nyob ib ncig ntawm nws tus kheej.

Thaum ntau qhov chaw tsim, nws txo qis. Lub zog ntawm depolarization kuj txo, tab sis lub zog ntawm cov phab ntsa sector nce. Cov txheej txheem ua tiav thaum cov ntsuas no nyob hauv tib qho kev txiav txim.

Tus cwj pwm ntawm HSE yog dab tsi thaum ferroelectrics nyob rau sab nraud, tau piav qhia saum toj no.

Antiferroelectrics - assimilation ntawm tsawg kawg yog ob lub sublattices tso rau hauv ib leeg. Nyob rau hauv txhua tus, cov kev taw qhia ntawm dipole yam yog parallel. Thiab lawv qhov ntsuas dipole feem ntau yog 0.

Hauv cov spectra tsis muaj zog, antiferroelectrics txawv los ntawm ib hom kab ntawm polarization. Tab sis raws li lub teb lub zog nce, lawv tuaj yeem tau txais ferroelectric tej yam kev mob. Field parameters tsim los ntawm 0 mus rau E _1. Polarization loj hlob linearly. Ntawm qhov rov qab txav mus, nws twb tau tsiv tawm ntawm thaj teb - ib lub voj tau txais.

Thaum lub zog ntawm ntau yam E _{2 yog tsim,} ferroelectric hloov mus rau nws cov antipode.

Thaum hloov lub teb vector E, qhov xwm txheej zoo ib yam. Qhov no txhais tau hais tias qhov nkhaus yog symmetrical.

Antiferroelectric, tshaj qhov Curie cim, tau txais cov kab mob paraelectric.

Nrog rau qhov qis dua mus rau qhov no, qhov permeability nce mus txog qhov siab tshaj plaws. Saum toj no, nws txawv raws li Curie-Weiss mis. Txawm li cas los xij, qhov tseeb permeability parameter ntawm qhov taw tes qhia yog qis dua ntawm ferroelectrics.

Ntau zaus, antiferroelectrics muajcrystalline qauv akin rau lawv cov antipodes. Hauv cov xwm txheej tsis tshua muaj thiab nrog cov sib xyaw sib xyaw, tab sis ntawm qhov kub sib txawv, theem ntawm ob qho tib si pyroelectrics tshwm sim.

Cov tshuaj tiv thaiv nto moo tshaj plaws yog NaNbO _3, NH ₄ H ₂ P0 4 _{lwm yam. Lawv tus lej qis dua tus lej ntawm cov ferroelectrics.}