Medium permittivity bismuth zinc niobate thin film capacitors

Thin films were fabricated via metalorganic decomposition methods with three compositions: ${\mathrm{Bi}}_{\text{1.5}}{\mathrm{Zn}}_{\text{1.0}}{\mathrm{Nb}}_{\text{1.5}}{\mathrm{O}}_7,$ ${\mathrm{Bi}}_{\text{1.5}}{\mathrm{Zn}}_{\text{0.5}}{\mathrm{Nb}}_{\text{1.5}}{\mathrm{O}}_{\text{6.5}},$ and ${\mathrm{Bi}}_2{\mathrm{Zn}}_{\text{2/3}}{\mathrm{Nb}}_{\text{4/3}}{\mathrm{O}}_7.$ The ${\mathrm{Bi}}_{\text{1.5}}{\mathrm{Zn}}_{\text{0.5}}{\mathrm{Nb}}_{\text{1.5}}{\mathrm{O}}_{\text{6.5}}$ composition is a low temperature phase with the cubic pyrochlore structure. This phase may undergo a peritectoid decomposition at $\text{700\hspace{0.05em}°}\mathrm{C}$ to the high temperature phases of ${\mathrm{Bi}}_{\text{1.5}}{\mathrm{Zn}}_{\text{1.0}}{\mathrm{Nb}}_{\text{1.5}}{\mathrm{O}}_7$ and ${\mathrm{BiNbO}}_4.$ Both the ${\mathrm{Bi}}_{\text{1.5}}{\mathrm{Zn}}_{\text{1.0}}{\mathrm{Nb}}_{\text{1.5}}{\mathrm{O}}_7$ and ${\mathrm{Bi}}_{\text{1.5}}{\mathrm{Zn}}_{\text{0.5}}{\mathrm{Nb}}_{\text{1.5}}{\mathrm{O}}_{\text{6.5}}$ cubic pyrochlores show medium room temperature permittivities (150 and 180, respectively) with negative temperature coefficients of capacitance and a low temperature dielectric relaxation. Both ${\mathrm{Bi}}_{\text{1.5}}{\mathrm{Zn}}_{\text{1.0}}{\mathrm{Nb}}_{\text{1.5}}{\mathrm{O}}_7$ and ${\mathrm{Bi}}_{\text{1.5}}{\mathrm{Zn}}_{\text{0.5}}{\mathrm{Nb}}_{\text{1.5}}{\mathrm{O}}_{\text{6.5}}$ films showed substantial dielectric tunability with electric field $\text{(>30\%).}$ The field dependence of the dielectric permittivity of the zirconolite structured ${\mathrm{Bi}}_2{\mathrm{Zn}}_{\text{2/3}}{\mathrm{Nb}}_{\text{4/3}}{\mathrm{O}}_7$ thin films demonstrates an unusual field induced transition at high field $\text{∼2\hspace{0.17em}}\mathrm{MV/cm},$ with a maximum tunability of 20%. It is hypothesized that this is associated with field forced ordering of the Zn atoms between two closely spaced, partially occupied sites.