Microwave dielectric tangent losses in KDP and DKDP crystals

Upadhyay, Trilok Chandra; Semwal, B. S.

doi:10.1007/bf02706161

Cited by 3 publications

(5 citation statements)

References 18 publications

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“…In present study, a two-sublattice pseudospin-lattice coupled mode model 9 along with third-and fourth-order phonon anharmonic interactions terms 19 for Rochelle salt has been used. By applying double-time thermal Green's function method 20…”

Section: Research Articlementioning

confidence: 99%

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Study of Dielectric Constant and Loss Tangent of Rochelle Salt Crystal

2016

Chem Sci Trans

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A two sub-lattice pseudospin-lattice coupled mode model along with third and fourth order phonon anharmonic interactions terms is considered for Rochelle salt. Double Time temperature dependent Green's function method is used for development. Expression for shift, width, renormalized soft mode frequency, Curie temperature, dielectric constant and loss tangent have been derived. Model values of physical quantities are fitted. Theoretical results were compared with experimental results of literature, which show a good agreement.

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Section: Research Articlementioning

confidence: 99%

“…Differentiating Eq. (2) twice with respect to time t and ' t with the help of Hamiltonian (1b), Fourier transforming it and setting into Dyson's equation form 19 .…”

Section: Theorymentioning

confidence: 99%

Study of Dielectric Constant and Loss Tangent of Rochelle Salt Crystal

2016

Chem Sci Trans

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“…Busch [4] was the first to show that KDP (KH 2 PO 4 ) exhibits a phase transition at low temperature. KDP is prototype of a family of crystals with bridging hydrogen bonds and its physical properties have been extensively studied [3,[5][6][7][8][9][10]. Kaminow and Damen [11] first observed the soft mode associated with the ferroelectric phase transition of the KDPtype crystal at 122.3 K by measuring the low frequency Raman scattering in ( ) configuration.…”

Section: Introductionmentioning

confidence: 99%

Study of Dielectric Properties and Ultrasonic Attenuation in KDP-Type Ferroelectrics

Bist

Panwar

2016

Physics Research International

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The soft mode dynamical model has been used to study dielectric properties and ultrasonic attenuation in KDP-type ferroelectric crystals. The model Hamiltonian proposed by Blinc and Zeks has been modified by considering lattice anharmonicity up to fourth-order. The correlations appearing in the dynamical equation have been evaluated using double-time thermal retarded Green’s functions method and Dyson’s equation. Without any decoupling, the higher order correlations, appearing in the dynamical equation, have been evaluated using the renormalized Hamiltonian. The expressions for collective frequencies, width, dielectric constant, ultrasonic attenuation, and tangent loss have been calculated. The dielectric properties and ultrasonic attenuation strongly depend on the relaxational mode behavior of stochastic motion of H2PO4group in KDP-type ferroelectrics. By fitting model values of physical quantities, the temperature dependence ofSqzandSqxfor different value of four-body coupling coefficient and dielectric constant and loss tangent has been calculated. The calculated and observed results have been found in good agreement.

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“…It was first shown by Bush 1 that potassium dihydrogen phosphate, KDP (KH 2 PO 4 ), exhibits a phase transition at low temperature. KDP is prototype of a family of crystals with bridging hydrogen bonds and its physical properties have been extensively studied [2][3][4][5][6][7][8][9][10][11][12][13] . Above the Curie temperature (T c ), KDP has tetragonal structure belonging to space group Fdd2 C V and exits at room temperature lower than T c = 123 K. In the ferroelectric phase the positions of all hydrogen are fixed to PO 4 radicals and a spontaneous polarization appears along the c-axis, and is not attributed directly to hydrogen, but to the displacement of K + ions and deformation of the tetrahedra of PO 4 radicals which are induced by the ordered arrangement of hydrogen.…”

Section: Introductionmentioning

confidence: 99%

“…At first, Pak 25 employed Green's function methods in the order-disorder type ferroelectrics, who however, did not consider the anharmonic interactions. The phonon anharmonic interactions have been found very important in explaining dielectric, thermal and scattering properties of solids by many authors [9][10][11][12][13]26 in the past. Pak's theory was further developed by Ramakrishanan and Tanaka 27 , who calculated the excitation spectrum of the system, but did not consider the anharmonic interactions.…”

Section: Introductionmentioning

confidence: 99%

Phase Transitions in KDP-Type Crystals

2015

Chem Sci Trans

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Curie temperature is determined by investigating the variation of order-parameter   S z q with temperature. The model Hamiltonian proposed by Blinc and Zeks has been modified by considering the lattice anharmonicities up to fourth order. The correlations appearing in the dynamical equation have been evaluated using double-time thermal retarded Green's function and Dyson's equation. The expressions for shift, width, renormalized soft mode frequency, Curie temperature, the expectation value of the proton collective mode components at site q , (  S z q and)   S x q have been derived and discussed in KDP-type crystals. By fitting model values of physical quantities, the temperature dependence of ,   S z q and   S x q for different value of four-body coupling have been calculated. The theoretical results are found in good agreement with the experimental results.

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Microwave dielectric tangent losses in KDP and DKDP crystals

Cited by 3 publications

References 18 publications

Study of Dielectric Constant and Loss Tangent of Rochelle Salt Crystal

Study of Dielectric Constant and Loss Tangent of Rochelle Salt Crystal

Study of Dielectric Properties and Ultrasonic Attenuation in KDP-Type Ferroelectrics

Phase Transitions in KDP-Type Crystals

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