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Processing of Barium Zinc Tantalate (BZT) Microwave Dielectric Ceramics for RF Window Application in Fusion Reactor

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Handbook of Advanced Ceramics and Composites

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Abstract

The ever-increasing energy demand by the human civilization and rapid depletion of conventional fossil fuel has triggered the scientists and engineers to look for alternative source of energy. Fusion energy, where four hydrogen nuclei combine to produce one helium nucleus with subsequent release of enormous amount of energy, could very well meet the future energy demand. Radio-frequency (RF) power is used as one of the noninductive methods to maintain the fusion plasma current under steady-state condition. RF window, used in the transmission line, acts as a vacuum barrier and transmits the microwave (MW) power to the plasma and hence a very critical component in the transmission line. Microwave dielectric ceramics, with high-quality factor/low loss, high dielectric constant, good temperature stability, high dielectric strength, high thermal conductivity, high mechanical strength, and ability to braze to the base metal, are most preferred materials for RF window application. High-purity dense alumina ceramics is the most common material for such application as of now. But the lower dielectric constant of Al2O3 ceramic poses a serious problem in thermal management of the window sections, and hence an alternate material is preferred. Barium zinc tantalate Ba(Zn1/3Ta2/3)O3 (BZT) is a well-known microwave dielectric ceramics with excellent properties such as high dielectric constant (εr), low loss (tanδ), very low temperature coefficient of resonance frequency (τf), and high-quality factor in the microwave frequency range and hence could be a potential candidate for MW window application. But, the major drawback in processing BZT ceramics at high temperatures is the volatilization of low-melting Zn from the BZT composition rendering the final product containing lot of defects including the presence of other phases. This chapter deals with the processing of BZT ceramics with properties suitable for RF window application. The effect of processing conditions and sintering techniques on development of mechanically robust BZT ceramics with highest density (close to the theoretical density), high dielectric constant, low loss (high-quality factor, Q), very low and stable temperature coefficient of resonance frequency, and high thermal conductivity has been discussed in detail.

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Abbreviations

BKZT:

Ba1-xKx(Zn(1-x)/3Ta(2 + x)/3)O3

BLZT:

Ba1-xLax(Zn(1 + x)/3Ta(2-x)/3)O3

BLZTG:

Ba1-xLax(Zn(1 + x-2y)/3Ta(2-x-y)/3Gay)O3

BMN:

Ba (Mg1/3Nb2/3)O3

BMT:

Ba(Mg1/3Ta2/3)O3

BZN:

Ba(Zn1/3Nb2/3)O3

BZT:

Barium zinc tantalate (Ba(Zn1/3Ta2/3)O3

BZT–SGT:

0.95BaZn1/3Ta2/3O3–0.05SrGa1/2Ta1/2O3

DRs:

Dielectric resonators

EM:

Electromagnetic

FWHM:

Full width at half maxima

LHCD:

Lower hybrid current drive

MLCC:

Multilayer ceramic capacitors

MW:

Microwave

POP:

Plaster of paris

RF:

Radio-frequency

SEE:

Secondary electron emission

SEM:

Scanning electron microscope

TD:

Theoretical density

UHV:

Ultrahigh vacuum

XRD:

X-ray diffraction

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Authors and Affiliations

  1. School of Engineering Sciences and Technology (SEST), University of Hyderabad, Hyderabad, India

    Swathi Manivannan & Dibakar Das

Authors
  1. Swathi Manivannan
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  2. Dibakar Das
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Correspondence to Dibakar Das .

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Editors and Affiliations

  1. ARCI, International Advanced Research Centre f ARCI, Hyderabad, India

    Yashwant Mahajan

  2. ARCI, International Advanced Research Centre f ARCI, Hyderabad, Telangana, India

    Johnson Roy

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  1. No affiliation provided

    Tetsuji NODA

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Manivannan, S., Das, D. (2019). Processing of Barium Zinc Tantalate (BZT) Microwave Dielectric Ceramics for RF Window Application in Fusion Reactor. In: Mahajan, Y., Roy, J. (eds) Handbook of Advanced Ceramics and Composites. Springer, Cham. https://doi.org/10.1007/978-3-319-73255-8_24-1

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  • DOI: https://doi.org/10.1007/978-3-319-73255-8_24-1

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