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Electrical and Thermal Properties of Na1-xLixNbO3 (x = 0.08, 0.1 and 0.2) Ceramics Near the Morphotropic Phase Boundary Region

Konieczny K., Czaja P.

Archives of Metallurgy and Materials

2017

Vol. 62, iss. 2A

539--544

Na1-xLixNbO3 ceramics (for x = 0.08, 0.1, 0.2) were fabricated by the conventional solid state reaction method. The influence of LiNbO3 on the microstructure, electric, thermal properties of Na1-xLixNbO3 ceramics was studied and a significant influence of doped Li ions on the electrical properties was observed. The electrical properties were improved and are described as the best for x = 0.1 (near a morphotropic phase boundary) Na1-xLixNbO3 solid solutions. After crossing the morphotropic phase boundary for x = 0.2, the electric properties are getting worse. These types of solid compounds show some interesting properties suitable for practical applications.

Analysis of the Phase Transitions in BNT-BT Lead-Free Ceramics Around Morphotropic Phase Boundary by Mechanical and Dielectric Spectroscopies

Silva Jr P. S., Diaz J. C. C. A., Florêncio O., Venet M., M’Peko J. C.

Archives of Metallurgy and Materials

2016

Vol. 61, iss. 1

17--20

In this work, the syntheses and characterization by mechanical and dielectric spectroscopies of (1-x) Bi0.5Na0.5TiO3-xBaTiO3 (BNT-100xBT), with x = 0.05, 0.06 and 0.07, lead-free piezoelectric ceramics is reported. Ceramic samples of BNT-BT have been prepared by mixed-oxide method and then conventionally sintered. X-ray diffraction patterns of sintered samples, indicated for BNT-7BT the presence of tetragonal (P4mm) complex perovskite structure, whereas for BNT-5BT and BNT-6BT the samples exhibit a mixture of tetragonal (P4mm) and rhombohedral (R3c) crystalline phases, which reveal the presence of a morphotropic phase boundary (MPB) in the BNT-BT system. Measurements of internal friction, Q-1, and the storage modulus, E’, as a function of temperature at various frequencies were carried out in a Dynamic Mechanical Analyzer (DMA), in the temperature range from 0ºC to 600ºC. Dielectric profiles are recorded in the frequency range from 1kHz to 100kHz and the temperature range from room temperature to 475ºC. Mechanical loss spectra obtained for investigated compositions of BNT-BT samples showed different frequency-independent anomalies. Two main anomalies for BNT-5BT and BNT-6BT, observed around 100ºC and 430ºC were associated with the ferroelectric-antiferroelectric and antiferroelectricparaelectric phase transitions, respectively. The results obtained from mechanical loss measurements were supported by dielectric relaxation spectra. For BNT-7BT, outside the MPB, four different frequency-independent processes were observed.

Morphotropic phase boundary in Bi1-xCaxFe1-x/2Nbx/2O3 multiferroics

Troyanchuk I. O., Karpinsky D. V., Tereshko N. V., Fedotova V. V., Kopcewicz M., Kozak C.

Przegląd Elektrotechniczny

2013

R. 89, nr 3b

264--266

Investigation of crystal structure, magnetic and piezoelectric properties of polycrystalline Bi1-xCaxFe1-x/2Nbx/2O3 system was performed by X-ray diffraction, Mössbauer spectroscopy, Vibrating Sample Magnetometry (VSM), and Piezoresponse Force Microscopy (PFM). It is shown that increasing niobium content induces a polar-to-nonpolar morphotropic boundary near the x=0.19. The piezoresponse is significantly enhanced near the morphotropic boundary. The piezoelectric properties of parent antiferromagnet BiFeO3 with a cycloidal spatially modulated spin structure and polar weak ferromagnet Bi0.82Ca0.18Fe0.91Nb0.09O3 are compared and analyzed.

Struktura krystaliczna oraz właściwości magnetyczne i piezoelektryczne polikryształu Bi1-xCaxFe1-x/2Nbx/2O3 zostały zbadane przy użyciu dyfrakcji rentgenowskie, spektroskopii Mosswbauera, magnetometrii z wibrującą próbką (VSM) oraz mikroskopii odpowiedzi elektrycznej (PFM). Wykazano, że rosnąca zawartość niobu wymusza powstanie granicy morfotropowej pomiędzy obszarem polarnym i nie polarnym w pobliżu x=19. Odpowiedź piezoelektryczna jest znacząco lepsza w pobliżu granicy morfotropowej. Zbadano i porównano właściwości piezoelektryczne macierzystego antyferromagnetyka BiFeO3 z cykloidalnym modulowanym przestrzennie momentem spinowym oraz słabego ferromagnetyka polarnego Bi0.82Ca0.18Fe0.91Nb0.09O3.