P1F-4 Revisiting LGT Dielectric Constants and Temperature Coefficients Up to 120°C

Langatate (LGT) has been grown and characterized more intensively in the past decade and the reported acoustic wave properties of this relatively recent crystal have shown significant variations among different groups. Yet to be determined is how much of this dissimilarity is attributable to variations in the growth process or to different measurement techniques. For the dielectric permittivity, in particular, previously published values of epsiv
^S

₁₁
/epsiv
₀
differ from each other by as much as 33% while those of epsiv
^S

₃₃
/epsiv
₀
differ by up to 25% at room temperature. In this work, the dielectric constants of LGT are determined by measurements made from room temperature (25degC) up to 120degC. The permittivity was extracted from capacitance measurements using a precision LCR meter and computer controlled oven. LGT plates oriented along the X, Y, and Z crystalline axes were cut, ground, and polished to an optical finish at the University of Maine's Microwave Acoustic Lab facilities. The capacitor electrodes were deposited using an aerosol spray method chosen for ease of fabrication and to allow for multiple uses of each of the LGT sample. The measured relative dielectric constants reported in this work are: epsiv
^S

₁₁
/epsiv
₀
is 17.69 +/- 0.30 and epsiv
^S

₃₃
/epsiv
₀
is 70.73 +/- 1.24, which are 11.5% and 7.3% lower then an average of previously published values. The paper discusses the data provided and the associated uncertainties.