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The cubic pyrochlore Bi 1.5 MgNb 1.5 O 7 (BMN) thin films were deposited on Pt coated sapphire substrates by rf magnetron sputtering using different pressures. The effects of sputtering pressure on phase structure and dielectric properties of BMN thin films were investigated. The X-ray diffraction results revealed that all the BMN thin films deposited at different sputtering pressures showed a pure cubic pyrochlore phase, but the films sputtered at low pressure have a better crystalline than that sputtered at high pressure. The BMN thin films sputtered at 1 Pa exhibited good crystalline with a strong (222) preferred orientation and excellent dielectric properties, which have a dielectric constant of 80, dielectric loss of ~ 0.007, and dielectric tunability of ~ 38% at bias field of 1.25 MV/cm. The dielectric constant and tunability of BMN thin films were both decreased with increasing sputtering pressure. However, the dielectric loss showed a slightly change with the sputtering pressure. Furthermore, the leakage current density of BMN thin films increased with increasing sputtering pressure, which is suggested to be related with the increasing grain size and surface roughness of thin films sputtered at high pressure.

The cubic pyrochlore Bi 1.5 Mg N Nb 2.5 − N O 8.5 − 1.5 N (BMN) thin films with various compositions were deposited on Pt coated sapphire substrates by rf magnetron sputtering. Crystal structures of the BMN thin films by X-ray diffraction exhibited nearly pure cubic pyrochlore phase in a wide range of chemical substituents. The dielectric properties were systematically studied and discussed. The dielectric constant was found to increase with increasing Mg 2+ content, while the dielectric loss changed little with the Mg 2+ concentration and remained in a low level of ∼0.006. The BMN thin films with a composition of Bi 1.5 Mg 1.0 Nb 1.5 O 7 demonstrated a tunability of 20% at applied bias filed of 1.0 MV/cm. The insufficient Mg 2+ content decreased the tunability of the BMN thin films. However, the BMN thin films with excess Mg 2+ content also did not exhibit enhanced tunable performance. These results indicated that the appropriate Mg 2+ content and stoichiometric composition were of significance for improving the tunability of BMN thin films.

The Bi 1.5 MgNb 1.5 O 7 (BMN) thin films were prepared on Pt-coated sapphire substrates by rf magnetron sputter deposition. The as-deposited amorphous films were thermally treated for crystallization and formation of cubic pyrochlore structure. The effects of annealing treatment on microstructures and dielectric properties of BMN thin films have been investigated. X-ray diffraction detected cubic pyrochlore phases in the films annealed at 650 °C and above. The grain size and surface roughness of the films increased with annealing temperature. The as-deposited films and the films annealed up to 600 °C showed a low value of dielectric permittivity and high value of loss tangent. An abrupt increase in dielectric permittivity and a decrease in loss tangent appeared at 650 °C. The thin films annealed above 650 °C showed bias voltage dependence of the dielectric permittivity, and the tunability increased with annealing temperature. However, the leakage current density also increased at high annealing temperatures.

Bi1.5Zn1.0Nb1.5O7 (BZN)/Ba0.5Sr0.5TiO3 (BST) thin films were prepared on Pt/Ti-coated sapphire substrates by radio frequency magnetron sputtering. The specific relationship between the dielectric properties and the thickness ratio of the BZN thickness to the BST thickness was investigated. The presence of BZN films effectively reduced the dielectric loss of the thin films. The thickness-ratio-dependent dielectric constant and dielectric loss behaviors were in good accordance with the simulation results based on the series connection theory. The optimum thickness ratio was determined to be around 0.5, exhibiting a maximum commutation quality factor of about 16,000. The built-in electric field at the region near the BZN–BST interface may be responsible for the asymmetric characteristic of the electric-field-dependent dielectric properties of the BZN/BST thin films.

The Bi1.5MgNb1.5O7 (BMN) thin films were prepared on platinum coated sapphire by rf magnetron sputter deposition. Effects of substrate temperature, sputter pressure and O2/(O2 + Ar) mixing ratio on phase structures and dielectric properties of thin films were investigated. The results indicated that sufficiently high substrate temperature and low sputter pressure would facilitate the formation of cubic pyrochlore in BMN thin films. Meanwhile, the appropriate O2/(O2 + Ar) mixing ratio of sputter atmosphere was required. The deposited Bi1.5MgNb1.5O7 cubic pyrochlore thin films with (222) oriented texture exhibited large tunability of ~ 50% at a maximum applied bias field of 1.5 MV/cm, with low dielectric loss of ~ 0.007. The temperature and frequency dependent dielectric measurements indicated that no noticeable dielectric dispersion was detected in BMN cubic pyrochlore thin films.