Structure property relations in La(Mg{sub 1/2}Ti{sub 1/2})O{sub 3}-based solid solutions

Journal Article · Tue Feb 01 04:00:00 EST 2005 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.1834980· OSTI ID:20665089

Seabra, M P; Ferreira, V M; Zheng, H; Reaney, I M ^[1]

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1. Department of Ceramics and Glass Engineering, Centre for Research in Ceramics and Composite Materials (CICECO), University of Aveiro, 3810-193 Aveiro (Portugal)

Ceramics based on (1-x)La(Mg{sub 1/2}Ti{sub 1/2})O{sub 3} (LMT)-xATiO{sub 3} solid solutions, where A=Ca, Sr, and Ba, have been investigated to study the effect of average A-site ionic radius on structure and microwave dielectric properties. X-ray diffraction (XRD), transmission electron microscopy (TEM), and Raman spectroscopy were used to study the structural changes and planar defects and thereby interpret changes in microwave properties. 1:1 rocksalt ordering between Mg{sup 2+} and Ti{sup 4+} in LMT was destroyed for all samples in which x>0.1. XRD and TEM revealed that all (1-x)LMT-xCaTiO{sub 3} (LMTCT), x{<=}0.9, were distorted through a combination of antiphase and in-phase octahedral rotations (tilted). For (1-x)LMT-xSrTiO{sub 3} (LMTST) this combination is present until x=0.5, and for x>0.5 only antiphase tilting exists. For (1-x)LMT-xBaTiO{sub 3} (LMTBT), in-phase and antiphase octahedral distortions were only present for x{<=}0.3, x=0.5 was tilted in antiphase and x{>=}0.7 was untilted. The temperature coefficient of resonant frequency ({tau}{sub f}) varied linearly with relative permittivity ({epsilon}{sub r}) for LMTCT and LMTST but a discontinuity was observed for LMTBT at x{approx_equal}0.7, the composition at which octahedral rotations are no longer present at room temperature. Zero {tau}{sub f} was achieved at x{approx_equal}0.5 in all solid solution series. In general, the microwave dielectric quality factor (Qf{sub o}) decreased with increasing x to a minimum at x=0.5 for all solid solution series followed by an increase at x=0.7 despite {epsilon}{sub r} being higher for x=0.7 than for 0.5. Qf{sub o} then continued to decrease as x=1 was approached and {epsilon}{sub r} increased.

• OSTI ID: 20665089
• Journal Information: Journal of Applied Physics, Journal Name: Journal of Applied Physics Journal Issue: 3 Vol. 97; ISSN JAPIAU; ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
BARIUM COMPOUNDS
CALCIUM COMPOUNDS
CERAMICS
DIELECTRIC MATERIALS
LANTHANUM COMPOUNDS
MAGNESIUM COMPOUNDS
MAGNESIUM IONS
OXIDES
PERMITTIVITY
QUALITY FACTOR
RAMAN SPECTRA
RAMAN SPECTROSCOPY
SOLID SOLUTIONS
STRONTIUM COMPOUNDS
TEMPERATURE COEFFICIENT
TEMPERATURE RANGE 0273-0400 K
TITANIUM COMPOUNDS
TITANIUM IONS
TRANSMISSION ELECTRON MICROSCOPY
X-RAY DIFFRACTION