Enhanced stability of magnetoelectric gyrators under high power conditions Chung Ming Leung, Xin Zhuang, Min Gao, Xiao Tang, Junran Xu, Jiefang Li, Jitao Zhang, G. Srinivasan, and D. Viehland
Citation: Appl. Phys. Lett. 111, 182901 (2017); View online: https://doi.org/10.1063/1.5001287 View Table of Contents: http://aip.scitation.org/toc/apl/111/18 Published by the American Institute of Physics
Articles you may be interested in Moving towards the magnetoelectric graphene transistor Applied Physics Letters 111, 182402 (2017); 10.1063/1.4999643 Highly efficient solid state magnetoelectric gyrators Applied Physics Letters 111, 122904 (2017); 10.1063/1.4996242 Non-local electrical spin injection and detection in germanium at room temperature Applied Physics Letters 111, 182401 (2017); 10.1063/1.5003244 Insights into antiferroelectrics from first-order reversal curves Applied Physics Letters 111, 182902 (2017); 10.1063/1.5003612 Magnetic memory effect at room temperature in exchange coupled NiFe2O4-NiO nanogranular system Applied Physics Letters 111, 182406 (2017); 10.1063/1.4997518 Optically and electrically co-controlled resistance switching in complex oxide heterostructures Applied Physics Letters 111, 172901 (2017); 10.1063/1.4986864
APPLIED PHYSICS LETTERS 111, 182901 (2017)
Enhanced stability of magnetoelectric gyrators under high power conditions Chung Ming Leung,1,a) Xin Zhuang,1 Min Gao,1 Xiao Tang,1 Junran Xu,1 Jiefang Li,1 Jitao Zhang,2 G. Srinivasan,2 and D. Viehland1 1
Department of Materials Science and Engineering, Virginia Tech, Blacksburg, Virginia 24060, USA Physics Department, Oakland University, Rochester, Michigan 48309, USA
2
(Received 23 August 2017; accepted 14 October 2017; published online 31 October 2017) In this study, three different coil-based magnetoelectric (ME) gyrators of different geometries, including gyrators with high power output, have been designed and characterized. These included two magnetostrictive/piezoelectric/magnetostrictive (M-P-M) and one piezoelectric/magnetostrictive/piezoelectric (P-M-P) type ME gyrators, which consisted of nickel zinc ferrite (NZFO) and lead zirconate titanate (PZT) ceramic plates. Compared with M-P-M ME gyrators, the P-M-P ones exhibited a higher power efficiency (g) of 85% when operated at resonance under an optimal magnetic bias field (HBias) of 40 Oe at low power conditions. It retained a relatively high efficiency of g ¼ 79% under a high input power density of 2.87 W/cm3. A low reduction in the magnetomechanical coupling and mechanical quality (k33,m and Qm) factors of the NZFO ferrite layer in the ME gyrator explains the resilience of the P-M-P type structure with increasing power drive. The findings open the possibility of using ME gyrators in high power applications. Published by AIP Publishing. https://doi.org/10.1063/1.5001287 An important challenge in recent decades has been developing highly efficient power converters. Power conversion is an important technology that transforms electrical energy from one form to another, such as traditional step-up/down voltage-voltage and current-current conversions.1 In response to increasing requirements for small and portable devices, a number of small power converter devices have been developed ranging from electromagnetic to piezoelectric transformers and more recently I-V gyrators.1,2 The gyrator is an important passive electrical circuit element proposed by Tellegen in addition to the other four well-known elements (i.e., resistor, capacitor, inductor, and transformer).3 It offers a 2-port, 4-wire device with inductive and capacitance features, which is suitable for many power electronic device applications. However, selecting a material/device for passive power gyrators is not a simple task. Passive gyrators consisting of magnetoelectric (ME) composites were first reported by Zhai et al. who described the behavior of their current-voltage and voltage-current conversion features.4–6 However, they did not demonstrate the use of ME gyrators in power conversion. Recently, Leung et al. reported that ME gyrators were capable of high power conversion between two inductance/capacitance ports.7,8 Investigations revealed that the power conversion efficiency was based on a combination of stress/strain transfer properties between magnetostrictive and piezoelectric layers, enabling the possibility of power conversion by transferring power through the two ports of the ME laminates under low input power conditions. The power density level remained notable below that required for practical applications. Thus, a stable efficient ME gyrator working under high power drive conditions has remained a future target which needs to be achieved. In this paper, we report a tri-layer piezoelectric/magnetostrictive/piezoelectric (P-M-P) type coil-ME gyrator consisting of two Pb(Zr, Ti)O3 (PZT) piezoelectric ceramic a)
Author to whom correspondence should be addressed:
[email protected]
0003-6951/2017/111(18)/182901/4/$30.00
layers and one Ni0.8Zn0.2Fe2O4þ0.3 wt. % MnCO3 (NZFO) magnetostrictive ferrite plate wrapped by a copper coil, which achieved these requirements. Compared with previous reports of tri-layer magnetostrictive/piezoelectric/magnetostrictive (M-P-M) type NZFO/PZT/NZFO coil-ME gyrators, our proposed P-M-P gyrator provides a stable high power efficiency of 80% with the increasing high input power densities to the ME gyrator (PD-Gy) of up to 2.87 W/cm3. The improved high power performance is due to a lower decrease in the magnetomechanical coupling (k33) and mechanical quality (Qm) factors of the NZFO ferrite under a clamped mechanical stress applied by the two piezoelectric layers in the P-M-P ME structure. Figure 1(a) shows the core element of the proposed P-MP type coil-ME gyrator. For comparison, the structure of a previously reported M-P-M gyrator is also shown in Fig. 1(b). The core element of the P-M-P gyrator consisted of one Ni0.8Zn0.2Fe2O4þ0.3 wt. % MnCO3 (NZFO) magnetostrictive
FIG. 1. Schematic diagram of (a) the proposed P-M-P type coil-based ME gyrator and (b) M-P-M type coil-based ME gyrator.
111, 182901-1
Published by AIP Publishing.
182901-2
Leung et al.
Appl. Phys. Lett. 111, 182901 (2017)
ferrite layer sandwiched and bonded by two oppositely polarized hard Pb(Zr, Ti)O3 (PZT) piezoelectric ceramic plates using an adhesive epoxy. The Ni0.8Zn0.2Fe2O4þ0.3 wt. % MnCO3 (NZFO) magnetostrictive ferrite was synthesized by traditional ceramic techniques. All the constituent oxide powders (NiO, ZnO, Fe2O3, and MnCO3) were weighed and mixed with a solvent (Ethanol) in a ball mill for 24 h. After calcination, they were then pressed in a die under high pressure (20000 psi) and sintered at 1300 C for 5 h. The ferrite plate was cut to a length of 34 mm, a width of 5.5 mm, and a thickness of 1 mm, and the two PZT plates were cut with the same dimensions of width and thickness but had a different length of 20 mm. Electrical wires were connected to the upper and lower surfaces of the core element to provide a positive capacitance port, and an electrical wire was connected to the middle layer of the ME core by silver paint to provide a negative capacitance port, as shown in Fig. 1. For comparative purposes, a NZFO ferrite plate, a PZT ceramic plate, and two MP-M type coil-ME gyrators (M-P-M ME Gyrator I and M-PM ME Gyrator II) were prepared for testing. For the tests of k and Q factors, the ferrite layer was 34 mm in length, 5.5 mm in width, and 1 mm in thickness, and the PZT layer was 20 mm in length, 5.5 mm width, and 1 mm in thickness. The M-P-M gyrator I was constructed using two NZFO ferrites that were 28 mm in length, 5.5 mm in width, and 1 mm in thickness and one PZT ceramic plate that was 30 mm in length, 5.5 mm in width, and 0.5 mm in thickness, and the MP-M gyrator II was constructed using two NZFO ferrites that were 28 mm in length, 5.5 mm in width, and 0.5 mm in thickness and one PZT ceramic plate that was 30 mm in length, 5.5 mm in width, and 2.2 mm in thickness. For measurements, all samples were then placed in similar copper coils wound by 300 turns that were 34 mm in length. All characterizations and measurement of the ferrite and PZT plates and ME gyrators were performed at room temperature.7,8 The coupling coefficients (k33,m for magnetostrictive layers working in the 3-3 mode and k31,p for piezoelectric layers working in the 3-1 mode), mechanical quality factor (Qm), and power efficiencies (g) were measured using a dynamic signal analyzer (DSA) (SRS785).9 A swept sine wave input was provided by an ac power amplifier controlled by the signal output of the DSA. The signals from the samples were then measured simultaneously using the same DSA. The magnetic field bias (HBias) was produced by a water-cool electromagnet powered using a dc power amplifier. For high power drive testing, a digital mixed signal oscilloscope (Keysight MSOX3014T) was used to measure the power efficiency (g ¼ Pout/Pin) at the resonance frequency (fr). A 10 passive probe was applied when the voltage excessed 5 V. To analyze the relationship between the magnetomechanical coupling coefficients, mechanical quality factors, and power efficiency dependences at the input power level, three identical power density terms were defined: The input power density for magnetostrictive layers (PD-Ms), piezoelectric layers (PDPz), and ME gyrators (PD-Gy). The relationships between the power and volume were defined as follows: Pin ; PD-Ms ¼ VolMs
(1)
PD-Pz ¼
Pin ; VolPz
(2)
PD-Gy ¼
Pin ; VolGy
(3)
where Pin is the input power, VolMs is the volume of the magnetostrictive layer, VolPz is the volume of the piezoelectric layer, and VolGy is the total volume of the gyrator (the volume combination of magnetostrictive and piezoelectric layers). In power conversion measurements, the power density is defined as the output/transmitted power divided by the volume.13 However, in this paper, the input power density was used, which made it easier to characterize the piezoelectric and magnetostrictive layers. Figure 2(a) shows k33,m and Qm for the NZFO ferrite layer and M-P-M and P-M-P ME gyrators as a function of HBias. It can be seen that k33,m initially increases significantly with increasing HBias and reaches maximum values of 0.124 at an optimal HBias of 40 Oe for the NZFO ferrite layer, 0.112 under HBias ¼ 80 Oe for the M-P-M ME gyrator I, 0.067 under HBias ¼ 50 Oe for the M-P-M ME gyrator II, and 0.0767 under HBias ¼ 40 Oe for the P-M-P ME gyrator. All samples were tested under a PD-Ms 48 mW/cm3. Compared with the NZFO ferrite layer, both k33,m and Qm of the M-P-M and P-M-P gyrators were found to have lower values, which is due to the mechanical load produced by the piezoelectric ceramic plates. The dependence of k33,m, k31,p, and Qm of the
FIG. 2. (a) k33,m and Qm versus HBias for the NZFO ferrite layer and M-P-M and P-M-P ME gyrators. (b) k33,m and k31,p and Qm of the NZFO layer and M-P-M and P-M-P ME gyrators and the PZT layer as a function of PD-Ms/ PD-Pz at the optimal HBias.
182901-3
Leung et al.
NZFO ferrite and PZT layers and M-P-M and P-M-P ME gyrators operating at an optimal HBias was then measured as a function of PD-Ms/PD-PZ. The results are shown in Fig. 2(b). Both k33,m and Qm decreased with increasing PD-Ms for the NZFO ferrite layer and M-P-M and P-M-P gyrators. For the NZFO ferrite plate, there were reductions of -21% and -54% in k33,m and Qm factors, respectively; for the M-P-M ME gyrator I, reductions of -24% and -15.6% were found; for the M-P-M ME gyrator II, reductions of -28% and -12.7% were found; and for the P-M-P gyrator, smaller reductions of -21% and -4% were obtained. All measurements were performed in the PD-Ms/PD-Pz range of 0.048 to 2.14 W/cm3. For the PZT ceramic plates, no significant reduction in either k31,p or Qm factors was found, indicating good stability at high drive power levels. Because of the different mechanical load (clamping) conditions on the single (both) surface(s) of the ferrite layer(s), reinforcement benefits in the ferrite layers were achieved by one (or sandwich) piezoelectric layer when operated in a longitudinal tension and compressive resonance mode. The epoxy and piezoelectric layers distribute the loads with the ferrite layer in tension and thus mechanically stabilize the ferrite layer, preventing it from even buckling in compression.10 The sandwich structure thus imparts to the P-M-P type ME gyrator a low reduction rate in k33,m and Qm with increasing high power input drive. Next, the power efficiency (g) was measured as a function of the resistance load (RL) for the P-M-P ME gyrator and M-P-M ME gyrators I and II at their resonance frequencies (fr) under their optimal biases of HBias ¼ 40, 80, and 50 Oe, respectively (Fig. 3). The value of g initially increased with an increase in RL, reaching a maximum value between 500 and 1800 X. This determined the optimum efficiency values of g ¼ 85%, 82%, and 83% for the P-M-P ME gyrator and M-P-M ME gyrators I and II, respectively, which subsequently decreased slightly with a further increase in RL. It is known that the optimal value of the efficiency reaches a maximum when the resistance load is equal to 1/(xC0), which is called the matching load.11 This dependency of g on RL is similar to previous findings for Terfenol-D based ME gyrators.8 Figure 4 shows the efficiency g as a function of PD-Gy for the M-P-M and P-M-P gyrators while operating at their
FIG. 3. Power conversion efficiency (g) as a function of resistive load (RL) for M-P-M and P-M-P ME gyrators under optimal HBias.
Appl. Phys. Lett. 111, 182901 (2017)
FIG. 4. Maximum g of the M-P-M and P-M-P ME gyrators as a function of PD-Gy.
optimal HBias and RL. For the P-M-P gyrator, a relatively small decrease in g from about 85% to 79% was found with increasing PD-Gy up to 2.87 W/cm3, compared to a decrease from 82% to 63% for the M-P-M ME gyrator I and a decrease from 83% to 68% ME for gyrator II. The advantages of the P-M-P gyrator, relative to the M-P-M one, are due to lower reductions in k33,m and Qm of the NZFO ferrite layers for the P-M-P construction. The stable power efficiency allowed the P-M-P gyrator to maintain a higher power efficiency under increasing high power densities. The efficiency and power density of the ME gyrators are dependent on Qm, k33,m, and k31,p. Materials with a high mechanical quality factor and coupling coefficient are preferred in ME gyrator applications. Compared to other magnetostrictive materials (e.g., Terfenol-D), NZFO ferrite has relatively small coupling coefficients but significantly higher Qm values. The high Qm enhances its power efficiencies at low power conditions. Based on our findings for k33,m and Qm factors in Fig. 2, the relatively low rates of coefficient reduction for P-M-P type ME gyrators are due to the uniformity of the stress transmitted to it through the epoxy and the piezoelectric layers. This uniform stress also reduces the chance of failure of the NZFO layer. Figure 5 shows the efficiency g and resonance frequency fr as a function of the operational time under a continuous high power drive condition of PD-Gy ¼ 2.87 W/cm3 for 20 min. The results clearly show that the P-M-P gyrator has a stable
FIG. 5. Power efficiency stability and resonance frequency as a function of time for M-P-M and P-M-P ME gyrators when continuously operated under a power density of PD-Gy ¼ 2.87 W/cm3 for 20 min.
182901-4
Leung et al.
efficiency of g ¼ 79% under high drive. A small 200 Hz shift in fr was found for the P-M-P gyrator after continuous drive, compared with a 700 Hz shift for the M-P-M ME gyrator I and a 500 Hz shift for the M-P-M ME gyrator II. In piezoelectric transducers, a low frequency shift indicates a high stability performance for high power drive applications. This high stability performance will enable the ME gyrator to be used in high power conditioning applications and increase the power-to-volume ratio by reducing the size of the power supply units.12 In summary, a P-M-P type ME gyrator was fabricated by sandwiching a NZFO ferrite plate between two PZT ceramic ones. It was designed to enhance the stability of both the magnetomechanical coupling and mechanical quality (k33,m and Qm) factors. The results demonstrate that the P-M-P gyrator has a power efficiency that is very stable with increasing input drive up to power densities as high as PDGy ¼ 2.87 W/cm3 for 20 min. This stability in efficiency with power density was better than that for M-P-M gyrators. This work received the support of the DARPA (DSOMATRIX No. W911NF-15-1-0616). 1
N. Mohan and T. M. Undeland, Power Electronics: Converters, Applications, and Design (John Wiley & Sons, 2007). 2 E. Wells, “Comparing magnetic and piezoelectric transformer approaches in CCFL applications,” Analog Appl. J. Q1, 12–18 (2002), available at http://www.deyisupport.com/cfs-file.ashx/__key/telligent-evolutioncomponents-attachments/13-107-00-00-00-01-01-35/slyt125.pdf.
Appl. Phys. Lett. 111, 182901 (2017) 3
B. D. Tellegen, “The gyrator, a new electric network element,” Philips Res. Rep. 3(2), 81–101 (1948), available at https://www.nonstopsystems. com/radio/pdf-hell/article-tellegen-gyrator.pdf. 4 J. Zhai, J. Li, S. Dong, D. Viehland, and M. I. Bichurin, “A quasi (unidirectional) Tellegen gyrator,” J. Appl. Phys. 100(12), 124509 (2006). 5 J. Zhai, J. Gao, C. De Vreugd, J. Li, D. Viehland, A. V. Filippov, et al., “Magnetoelectric gyrator,” Eur. Phys. J. B 71(3), 383–385 (2009). 6 C. W. Nan, M. I. Bichurin, S. Dong, D. Viehland, and G. Srinivasan, “Multiferroic magnetoelectric composites: Historical perspective, status, and future directions,” J. Appl. Phys. 103(3), 031101 (2008). 7 C. M. Leung, X. Zhuang, J. Xu, G. Srinivasan, J. Li, and D. Viehland, “Power conversion efficiency and resistance tunability in coilmagnetoelectric gyrators,” Appl. Phys. Lett. 109(20), 202907 (2016). 8 C. M. Leung, X. Zhuang, J. Xu, J. Li, G. Srinivasan, and D. Viehland, “Importance of composite parameters in enhanced power conversion efficiency of Terfenol-D/PZT magnetoelectric gyrators,” Appl. Phys. Lett. 110(11), 112904 (2017). 9 X. X. Wang, X. G. Tang, and H. L. W. Chan, “Electromechanical and ferroelectric properties of (Bi 1=2 Na 1=2) TiO 3-(Bi 1=2 K 1=2) TiO 3BaTiO 3 lead-free piezoelectric ceramics,” Appl. Phys. Lett. 85(1), 91–93 (2004). 10 F. C. Campbell, Structural Composite Materials (ASM International, 2010). 11 S. Dong, J. F. Li, and D. Viehland, “Magnetoelectric coupling, efficiency, and voltage gain effect in piezoelectric-piezomagnetic laminate composites,” in Frontiers of Ferroelectricity (Springer, USA, 2006), pp. 97–106. 12 J. Hu, Y. Fuda, and T. Yoshida, “A study on the rectangular-bar-shaped multilayer piezoelectric transformer using length extensional vibration mode,” Jpn. J. Appl. Phys. 38(5S), 3208 (1999). 13 X. M. L opez-Fernandez, H. B. Ertan, and J. Turowski, Transformers: Analysis, Design, and Measurement (CRC Press, 2012).
