Power Loss Density Research Articles

Dispersion compensation design of high-density stacking RFSS absorbers for wideband applications

Abstract A dispersion compensation design absorber realized by high-density stacking resistive frequency selective surface (RFSS) is proposed for wideband applications. Firstly, the quantitative relationship between the equivalent impedance of RFSS and the permittivity of the effective media is constructed with the help of the transmission matrix method. The dispersion regulation of permittivity is achieved by changing the pattern and the square resistance of RFSS. In terms of absorber design, a uniform absorber with dispersion manipulation is developed as a precursor absorber. The uniform absorber has an absorption performance better than −8.5 dB above 2 GHz at normal incidence. The loss mechanism is analyzed in detail by electric field distribution and surface power loss density distribution, indicating that the uniform design cannot achieve thickness saving when extending to low frequency. Therefore, a dispersion compensation design absorber is proposed to extend −10 dB bandwidth to 1.64–28.8 GHz. Experiment results agree well with the simulation results, validating the analytic methods and design principles.

Multi-heterogeneous interfaces boost dielectric polarization in PBA-derived Co/MnO@NC ternary composites for electromagnetic wave absorption

The elaborate construction of multi-component composites has been deemed as a promising strategy to enhance dielectric polarization response capability in the preparation of highly efficient microwave absorbers. However, the rational design and integration of homogeneous composites with diverse components continues to pose a great challenge. Herein, we propose a straightforward self-assembly-carbonization strategy for fabricating Co/MnO@NC ternary composites derived from CoMn-Prussian Blue Analogous precursors, featuring enriched heterogeneous interfaces and balanced magneto-electric coupling synergy. The ternary composites effectively introduce diverse dissipation mechanisms, including interfacial polarization behavior originated from the constructed heterogeneous interfaces, dipole polarization relaxation triggered by atomic defects, and optimized magnetic loss ability from well-dispersed metallic Co species. Benefiting from these advantages, the Co/MnO@NC composites demonstrate superior electromagnetic wave absorption performances, with a minimum reflection loss value of −61.37 dB at the thickness of 3.5 mm and effective frequency absorption bandwidth of 6.32 GHz, covering the full Ku-band. Furthermore, power loss density and radar cross-section simulations validate that the Co/MnO@NC ternary composites possess exceptional microwave signal attenuation abilities, with a maximum radar cross-section reduction value of up to 27.98 dBm2 at 0°. Such outstanding absorption properties exceed those of most currently reported ternary composites and exhibit significant potential to replace conventional ferromagnetic-based absorbers. This work offers a straightforward strategy to fabricate ternary composites with excellent electromagnetic wave attenuation properties and sheds novel insights into the dissipation mechanisms.

Switching figure-of-merit, optimal design, and power loss limit of (ultra-) wide bandgap power devices: A perspective

Power semiconductor devices are utilized as solid-state switches in power electronics systems, and their overarching design target is to minimize the conduction and switching losses. However, the unipolar figure-of-merit (FOM) commonly used for power device optimization does not directly capture the switching loss. In this Perspective paper, we explore three interdependent open questions for unipolar power devices based on a variety of wide bandgap (WBG) and ultra-wide bandgap (UWBG) materials: (1) What is the appropriate switching FOM for device benchmarking and optimization? (2) What is the optimal drift layer design for the total loss minimization? (3) How does the device power loss compare between WBG and UWBG materials? This paper starts from an overview of switching FOMs proposed in the literature. We then dive into the drift region optimization in 1D vertical devices based on a hard-switching FOM. The punch-through design is found to be optimal for minimizing the hard-switching FOM, with reduced doping concentration and thickness compared to the conventional designs optimized for static FOM. Moreover, we analyze the minimal power loss density for target voltage and frequency, which provides an essential reference for developing device- and package-level thermal management. Overall, this paper underscores the importance of considering switching performance early in power device optimization and emphasizes the inevitable higher density of power loss in WBG and UWBG devices despite their superior performance. Knowledge gaps and research opportunities in the relevant field are also discussed.

Power Dissipation of Uniaxial Anisotropic/Interacting Polar Molecules with Linear Reaction Dynamics in an Alternating Electric Field.

The influence of anisotropic potential energy and interaction between polar molecules on power absorption in chemical reactions with linear reaction dynamics in a weak alternating electric field is studied theoretically according to the reaction-diffusion equation. The expression for transient power loss is derived using two methods, electrodynamic method and equivalent circuit method, based on the electric energy conservation equation. Numerical calculations are carried out, and the results show that both the anisotropic potential energy and the interaction between polar molecules have a strong impact on energy dissipation and storage. For the anisotropic potential energy, when the applied dimensionless anisotropy is equal to 1, the power loss density increases about 32% at a low reaction rate and 27% at a high reaction rate compared to the case without anisotropic potential energy. When the dimensionless anisotropy is equal to -1, the power loss is suppressed and is reduced about 27% and 24% at low and high reaction rates, respectively. On the other hand, for the interaction between polar molecules, the power loss density decreases about 10% and 30% with low and high interaction potential energies, respectively. In addition, if the reaction rate is relatively high, the power loss will quickly decrease due to the end of the reaction process.

Honeycomb network structure constructed by silver nanoparticles achieving negative permittivity at low percolation threshold

Continuous conductive network is associated with the percolation effect, yet the method of fabricating network structure at low content is still a challenge. Herein, this work proposed a “honeycomb” structure via hot pressing to realize weak negative permittivity at low percolation threshold. By polydopamine (PDA) self-polymerization and silver mirror reaction plating, Ag nanoparticles coated polystyrene (PS) microsphere (PS@PDA@Ag) was prepared. Through hot pressing, the microspheres were compressed into “honeycomb”. The percolation threshold was reduced because the thin silver layer oscillated at low frequency plasma. Besides, by controlling the slivering time, weak negative permittivity in the range of −139 to −95 was observed and the percolation threshold was merely 2.23 vol%. The ac conductivity increased by four orders of magnitude and the thermal conductivity enhanced 79.08 %. The electric field and power loss density were simulated by finite element method. More than 100 V/m of electric field mode and 3 × 1011 W/m3 of power loss density were presented, explaining the generation of negative permittivity and the enhancement of dielectric loss. This work presented a method of achieving weak negative dielectric via honeycomb structure, and provided a novel perspective for the development of metal-based metacomposites.

Realization of an ultra-thin absorber based on magnetic metamaterial working at L-band

In this paper, at the L-band, we design and verify an ultra-thin easy-realized absorber (LUTA) based on metasurface and magnetic material. The absorptivity achieves over 90% at 1–2.51 GHz (86.04% fractional bandwidth), covering the whole L-band (1–2 GHz) and the partial S-band (2–4 GHz). The total thickness of the LUTA is as low as 3.7 mm, corresponding to 0.012λ0 at the lowest operating frequency, which greatly breaks through the Rozanov limit. The excellent performance is achieved through analyzing the transmission line model of a basic absorber and then designing the metasurface layer with required impedance characteristics to make the impedance of the LUTA match with the air at the designed frequency band. The simulated absorption, power loss density, and the surface current distributions of the LUTA verify the design method, while the measured results demonstrate that the LUTA has the superiority of easy-fabrication, polarization independent, wide angle incidence, and high absorption at the whole L-band. The LUTA has great application potentials in the fields of L-band electromagnetic stealth and radar cross section reduction.

Durability and kinetic effects of CO2-rich oxidizing streams on LSCF-based solid oxide fuel cells

In the SOS–CO2 cycle, a novel hybrid cycle for blue power production, the solid oxide fuel cell's (SOFC) cathode is supplied with a CO2-rich oxidizing stream (e.g., 21 % O2 79 % CO2 vol.). The durability of state-of-the-art anode-supported SOFCs (25 cm2, SolydEra) with LSCF-GDC/LSC (La0.6Sr0.4Co0.2Fe0.8O3-δ-Gd0.1Ce0.9O3+δ/La0.6Sr0.4CoO3+δ) cathodes was tested at atmospheric pressure for 1090 h with 7 % humidified H2 and reformate, at 700 °C and 0.85 V. The SOFC performance was investigated with periodic I/V curves and electrochemical impedance spectroscopy (EIS) measurements. The results highlighted a 24 % power density loss when air was replaced with the O2/CO2 mixture (672 mW/cm2 in air vs. 508 mW/cm2 in O2/CO2 with humidified H2). A stable power output was observed, and complete reversibility was found when the air supply was restored. A distribution of relaxation times (DRT) analysis of the EIS spectra allowed to extract an anodic rate equation for the hydrogen oxidation reaction (HOR) and evaluate the frequency region affected by cathodic CO2. The kinetic effect of CO2 was also studied via EIS on symmetric button cells at varying O2 and CO2 amounts, and a power-law rate equation was derived. The results verify the feasibility of the SOS–CO2 cycle feed conditions at 700 °C and atmospheric pressure.

S-doped carbon anchoring PtCo intermetallic nanoparticles for efficient proton exchange membrane fuel cells based on molecularly engineered design

Enhanced ordered intermetallic compounds excel in catalyzing the oxygen reduction reaction (ORR). We introduce a novel synthesis strategy based on molecularly engineered to address challenges in high-temperature annealing. It involves the synthesis of carbon platforms with rich edge sites, which serve as effective anchoring points for nanoparticles. By utilizing sulfur anchoring, we synthesize ordered Pt–Co intermetallic with Pt-rich shells (o-PtCo@Pt) that exhibit remarkable ORR performance. Ordered arrangement of Pt–Co endows Pt-shell with compression stress and enhances the oxidation resistance of Pt/Co sites. O–PtCo@Pt exhibits high mass activity (MA, 0.53 A mgPt−1) and specific activity (SA, 1.17 mA cm−2). It exhibits remarkable as cathodic catalyst in proton exchange membrane fuel cells. It achieves power density of 1.14 W cm−2 at 2.0 A cm−2, with MA of 0.50 A mgPt−1 at 0.9 V. It maintains stability with only 8 % power density loss after 30,000 cycles, retaining MA of 0.35 A mgPt−1.

Tuning the Multilevel Hierarchical Microarchitecture of MXene/rGO‐Based Aerogels Through a Magnetic Field‐Guided Strategy Toward Stepwise Enhanced Electromagnetic Wave Dissipation

AbstractHierarchical microarchitecture engineering is a state‐of‐the‐art approach to designing aerogel electromagnetic (EM) wave absorbers, offering huge potential in improving EM energy dissipation. However, the intrinsic feedback mechanism regarding the specific influence of each microarchitecture parameter on EM properties is not comprehensively revealed, making it challenging to fully utilize the potential of aerogels to achieve superior EM wave absorption performance. Herein, a range of MXene/rGO‐based aerogels with multilevel hierarchical configurations are fabricated by a magnetic field‐guided strategy. Leveraging growth thermodynamics effects under a magnetic field and bridging effect between adjacent rGO units, three hierarchical microarchitecture models (lamellae ordering, interlayer spacing, and layer thickness) are constructed in aerogels. Remarkably, three models progressively improve reflection loss (RL), effective absorption bandwidth (EAB), and matching thickness by enhancing dielectric loss, decoupling attenuation‐impedance matching, and adjusting power loss density, respectively. Consequently, the MXene/rGO‐based aerogels exhibit stepwise enhancement in EM wave performance, achieving a superior RL of −64.6 dB and a broad EAB of 7.0 GHz at 1.8 mm thickness, surpassing alternative aerogels with other configurations. This work elucidates the effect of multilevel hierarchical microarchitecture on the synergistic multi‐effect dissipation mechanism of EM waves in aerogels, providing insights for designing advanced EM absorbers through diverse strategies.

Introducing a 12/10 Induction Switched Reluctance Machine (ISRM) for Electric Powertrains

The induction switched reluctance machine (ISRM) is a novel electric machine that integrates the switched reluctance machine (SRM) with rotor inductive conductors to enhance performance in electric vehicle (EV) powertrain applications. In this topology, the rotor conductors act as a magnetic shield, diverting magnetic flux and preventing magnetic field lines from penetrating the rotor body. By engineering this design, short magnetic flux paths are created in both the stator and rotor of the electric machine. Since its recent introduction, the ISRM represents an emerging technology in the early stages of development. Similar to conventional SRMs, the ISRM can take on various topologies with different stator and rotor pole numbers. Minimizing rotor copper loss is a critical consideration in the ISRM design process. This paper examines two distinct ISRM topologies (12/10 and 12/8), and their characteristics are analyzed using the finite element method. Simulation results, including power density, torque density, efficiency, and copper loss, are presented and compared. Finally, the optimal ISRM topology is proposed for hybrid electric powertrains.

Research and simulation of electromagnetic wave absorbing performance for lightweight cement-based materials containing expanded polystyrene with different particle sizes and carbon black

The electromagnetic wave (EMW) absorbing performance of cement-based materials incorporating expanded polystyrene (EPS) with varying particle sizes is comprehensively studied through a combination of experimental and simulation methods. The addition of conductive carbon black (CB) to the cement matrix significantly increases the conductivity and dielectric constant, thereby improving the loss capacity. The frequency shift behavior of single and three-layer absorbing materials adheres to the effective medium theory and interference cancellation principle. The enhancement in overall EM parameters leads to a shift of the reflection loss (RL) peak towards lower frequencies. For three-layer materials, an increase in the thickness of absorbent layer proves beneficial for enhancing absorption performance. Simulations can effectively model cement-based materials by employing uniform material settings, with the size of EPS particles serving as the primary variable. The simulation results reveal that an increase in EPS particle size, in both single-layer and multi-layer materials, causes a shift of the RL peak towards lower frequencies. Additionally, analysis of electric field mode distribution and EM power loss density distribution indicates that scattering at the curved EPS interface alters the propagation direction of EMWs, increasing opportunities for loss inside the cement-based material. Moreover, the three-layer absorbing material, with a density ranging from 850 to 900 kg/m3 and compressive strength exceeding 4 MPa, is suitable for EMW absorption in building envelope structures. In conclusion, an increase in EPS particle size and CB content leads to a low-frequency shift of the RL absorption peak. This discovery not only provides an empirical foundation for the development of absorption materials tailored to specific frequency bands but also offers an efficient approach for repurposing waste EPS of diverse sizes. Furthermore, the grading of EPS with different particle sizes has important practical significance for increasing the content of EPS and preparing lightweight cement-based materials.

In-situ synthesis of Co/Co3O4 nanoparticles decorated carbon nanofiber aerogels for lightweight electromagnetic wave absorption rubber composites with multiple loss effects

Carbon-based magnetic absorbents are widely used for electromagnetic wave absorption (EMWA) rubber composites due to the dual electromagnetic wave loss effects of dielectric loss and magnetic loss. Co/Co3O4 nanoparticles decorated carbon nanofiber aerogels (C/Co/Co3O4 aerogels) are prepared by carbonization of nanofiber network structure agarose/cobalt acetate. The in-situ synthetic C/Co/Co3O4 aerogels with carbon nanofiber network structure and controllable particle size of Co/Co3O4 nanoparticles that have the good conductivity and tunable magnetic property increasing both of the dielectric loss and magnetic loss capabilities, which can improve the EMWA performance. Lightweight EMWA rubber composites with 3.75 wt% C/Co/Co3O4 aerogels have the same density as that of silicone rubber (PDMS), the effective absorption band (EAB, frequency for reflection loss<−10 dB) of PDMS/Co-1.25 is aways above 3 GHz when the thickness is bigger than 2.5 mm, the max EAB is 4.24 GHz at the thickness of 2.74 mm. The radar cross section (RCS) reduction can achieve 14 dBm2 when the perfectly electrically conductive (PEC) is covered by a 4.5 mm thick PDMS/Co-1.25. The intensity distributions of electric field, magnetic field and power loss density of EMWA rubber composites are exhibited based on the electromagnetic parameters. The rubber composites based on C/Co/Co3O4 aerogels can be used as lightweight flexible EMWA materials.

Numerical solution-based algorithm assisted development of a continuous flow microwave reactor

Continuous flow microwave heating is a sustainable technology favored in the chemical and food processing sectors due to its short residence time and relatively low environmental footprint. To address the complexity of fluid dynamics and electromagnetic field interactions, nuanced evaluation methods beyond conventional reflection coefficient analysis are necessary to predict its efficiency and uniformity. In this study, a numerical solution-based algorithm is utilized to propose synchrony and cumulative index metrics for performance analysis. Although identical S-parameter systems demonstrate approximate electromagnetic power loss density in the fluid region, significant disparities in heating performance are observed, evidenced by outlet temperatures ranging between 108.10 °C and 147.09 °C, and covariances ranging from 0.07 to 0.46. The power loss density is corrected based on velocity to introduce the synchrony index, which is further calculated into the cumulative index. This approach provides accurate predictions of efficiency and uniformity, informing system designs that align with specific performance objectives. To achieve the best uniformity in simulated two-part systems, a combination of 63 % GIM system and 37 % EBH-2 system in terms of power input was found to be optimal. However, when considering temperature dependent dielectric properties, the optimal combination was adjusted to 60 % GIM system and 40 % EBH-4 system. The numerical solution-based algorithm facilitates optimization of complex continuous flow microwave systems, providing invaluable insights into the time–space electromagnetic response mechanism of fluids.

Challenges in Measurement of Low-Value ESL and ESR of High-Performance PFN Capacitors for Klystron Modulator

In the high voltage line type pulse modulators, Pulse Forming Network (PFN) capacitors are one of the important components. These capacitors operate at peak kilo ampere current range and at repetition rate in the range of a few hundred hertz. The performance of these capacitors is critical w.r.t. overall system performance, and they are required to operate at high power density and low losses with high reliability. The Equivalent Series Inductance (ESL) and Equivalent Series Resistance (ESR) are two critical parameters that affect the performance of these capacitors. PFN modulator demands a capacitor of very low ESL and ESR for reliable operation and generation of high-voltage pulses. Higher ESR value adversely affects the performance of the capacitor by raising its temperature and thus deteriorating its life. ESL value does not directly affect life, but it affects the quality of high voltage pulse. In RRCAT, the PFN capacitors purchased from Indian manufacturers were showing high-temperature rise and failures. Therefore, new capacitors were designed to have lower ESL and ESR values. Measurement of ESL and ESR is important to evaluate the performance of the capacitors. The low value of these parameters makes their measurement a challenging task and requires special techniques. For low values of ESL and ESR (less than 100 mΩ) measurement, a differential measurement technique was used in which modification and different layouts were explored to improve the repetitive accuracy of the measurements. The differential ESR and ESL measurement techniques with more emphasis on the low-value ESR measurement will be discussed in the paper.

A low-frequency ultrathin metamaterial absorber using magnetic material

In this paper, an ultra-thin metamaterial absorber (UMA) in the S-band is designed. The overall structure adopts a three-layer design. The top layer is a magnetic material, and the middle layer of the UMA is composed of a centrally symmetrical open square ring (four edges are opened) and a circular pattern placed at the center, which is etched on the FR4 dielectric substrate by printed circuit board technology. The absorptivity of the absorber is more than 90% in 1.73–4.04 GHz under normal incidence, and the fractional bandwidth is 80.1%. The total thickness of the absorber is about 3.4 mm, corresponding to 0.02 λL at the lowest operating frequency. Moreover, it also has good polarization insensitivity and wide-angle incident characteristics. The absorption mechanism of the UMA is analyzed from the aspects of power loss density and surface current. Finally, a sample was fabricated and measured. The measured results are in good agreement with the simulation results, which verifies the effectiveness of the design method.

Boron-alloyed porous network platinum nanospheres for efficient oxygen reduction in proton exchange membrane fuel cells

Alloying (or doping) non-metals with platinum (Pt) is an advanced solution for the development of high-performance Pt-based electrocatalysts for oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs). Herein, we report boron (B)-alloyed Pt nanospheres (B-PtNSs) with a porous network nanostructure by a combination strategy of confinement reduction and post-boronation. B-alloying can induce effective electronic/geometric structures, strong Pt-B coordination, and lowered d-band center to weaken the binding energy of oxygenated intermediates on the Pt surface. The H2-O2 PEMFC with such a B-PtNSs/C as the cathode catalyst can reach a maximum power density of 1.49 W cm−2, about 1.28 times higher than that of Pt/C. After 30,000 voltage cycles in the range of 0.6 ∼ 0.95 V, only a 14.1 % loss of initial peak power density can be observed, while that with Pt/C declines 45.7 %. Non-metals alloying with Pt-based nanostructures can enable high-performance ORR electrocatalysts for their practical application in PEMFCs.

Dilute Nanocomposites: Tuning Polymer Chain Local Nanostructures to Enhance Dielectric Responses.

Dielectric polymers possessing high energy and low losses are of great interest for electronic and electric devices and systems. Nanocomposites in which high dielectric constant (high-K) nanofillers at high loading (>10 vol%) are admixed with polymer matrix have been investigated for decades, aiming at enhancing the dielectric performance, but with limited success. In 2017, it is discovered that reducing nanofiller loading to less than 0.5 vol% in polymer matrix can lead to marked enhancement in dielectric performance. Here, we reviewed the discoveries and advances of this unconventional approach to enhance dielectric performance of polymers. Experimental studies uncover that nanofillers lead to interfaceschanges over distances larger than 100nm. Experimental and modeling results show that introducing free volume in polymers reduces the constraints of glass matrix on dipoles in polymers, leading to enhanced K without affecting breakdown. Moreover, low-K nanofillers at low-volume loading serve as deep traps for charges, lowering conduction losses and increasing breakdown strength. The dilute nanocomposites provide new avenues for designing dielectric polymers with high K, minimal losses, and robust breakdown fields, thus achieving high energy and power density and low loss for operation over a broad temperature regime.

Sulfur doped iron-nitrogen-hard carbon nanosheets as efficient and robust noble metal-free catalysts for oxygen reduction reaction in PEMFC

Transition metal-nitrogen-carbon (M-N-C) as a promising substitute for the conventional noble metal-based catalyst still suffers from low activity and durability for oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs). To tackle the issue, herein, a new type of sulfur-doped iron-nitrogen-hard carbon (S-Fe-N-HC) nanosheets with high activity and durability in acid media were developed by using a newly synthesized precursor of amide-based polymer with Fe ions based on copolymerizing two monomers of 2, 5-thiophene dicarboxylic acid (TDA) as S source and 1, 8-diaminonaphthalene (DAN) as N source via an amination reaction. The as-synthesized S-Fe-N-HC features highly dispersed atomic FeNx moieties embedded into rich thiophene-S doped hard carbon nanosheets filled with highly twisted graphite-like microcrystals, which is distinguished from the majority of M-N-C with soft or graphitic carbon structures. These unique characteristics endow S-Fe-N-HC with high ORR activity and outstanding durability in 0.5 M H2SO4. Its initial half-wave potential is 0.80 V and the corresponding loss is only 21 mV after 30,000 cycles. Meanwhile, its practical PEMFC performance is a maximum power output of 628.0 mW cm−2 and a slight power density loss is 83.0 mW cm−2 after 200-cycle practical operation. Additionally, theoretical calculation shows that the activity of FeNx moieties on ORR can be further enhanced by sulfur doping at meta-site near FeN4C. These results evidently demonstrate that the dual effect of hard carbon substrate and S doping derived from the precursor platform of amid-polymers can effectively enhance the activity and durability of Fe-N-C catalysts, providing a new guidance for developing advanced M-N-C catalysts for ORR.

A multi resonant wave-absorbing honeycomb sandwich structure with excellent electrical performance damage tolerance

Wave-absorbing honeycomb sandwich structure (HSS) is widely used in aviation equipment, playing an important role in the integration of load-bearing and stealth shielding. The high-intensity service of aviation equipment beyond design condition accelerates damage and complicates failure triggers. In this work, a decentralized construction strategy with multiple resonant absorption peaks is proposed to enhance the electrical performance damage tolerance (EDT) of wave-absorbing HSS in 4–18 GHz frequency band. The designed multi resonant absorption peaks for 30 mm thick wave-absorbing honeycomb with 1 mm thick SiO2 fiber reinforced epoxy resin (SiO2f/ER) composites as top and bottom panels occur in the vicinity of 5 GHz, 9 GHz, 13 GHz, and 17 GHz, respectively. When the panel damage area accounts for 72 % or the penetrating damage area accounts for 18 %, the effective absorption bandwidth (EAB) of proposed HSS covers 4–18 GHz, indicating excellent EDT. By analyzing the normalized impedance, Smith chart, as well as power loss density, the excellent EDT is attributed to the pinning effect at each resonant frequency point, which benefits both impedance matching and electromagnetic wave (EMW) attenuation.

Energy relaxation rate and power loss density in graphene on GaAs substrate due to piezoelectric surface acoustic phonons

Electron-piezoelectric phonon interaction provides a significant extrinsic channel for energy relaxation in a graphene sheet placed on a polar substrate. We report in this paper our analytical and numerical investigations on energy relaxation rate and power loss density in graphene sheet on a polar substrate considering the electron-piezoelectric phonon scattering channel in the Boltzmann transport approach. We overcome the earlier crude approximations made to achieve the reported analytical results and compare the obtained results for their compliance with the numerical findings for the graphene sheet on the GaAs substrate. The obtained analytical expression for energy relaxation rate is valid for all temperatures and electron energies. The analytical result for power loss density limits its validity for low electron densities [Formula: see text]. It is observed that the relaxation rate due to surface piezoelectric phonons in graphene on GaAs substrate is directly proportional to temperatures above [Formula: see text], below which temperature independence is seen. Also, it is observed that the relaxation rate is linearly dependent on electron energy, [Formula: see text] at low temperatures, and [Formula: see text] independent at high temperatures. Moreover, the relaxation rate is electron density-independent for all (low to high) temperatures. The seemingly odd (from earlier reported behavior) temperature-independent, linearly dependent [Formula: see text] and n independent relaxation rate behavior for low temperatures is attributed to the approximation used so far in the phononic statistical occupation factor in deriving the relaxation rate in the low-temperature Bloch-Gruneisen (BG) regime. In undoped graphene, we have found that the power loss behavior follows a crossover from [Formula: see text] to [Formula: see text] behavior while moving from low [Formula: see text] to high [Formula: see text] electron temperature. This behavior contradicts the study by Zhang et al. [Phys. Rev. B 87, 075443 (2013)] and M. Ansari [Physica E: Low Dimens. Syst. Nanostruct. 131, 114722 (2021)] which reported low-temperature BG behavior of [Formula: see text]. This behavior is again attributed to using BG regime approximation for statistical occupation factors. Our findings are in agreement with the experimental work by Chen et al. [Nature Nanotechnol. 3, 206 (2008)] and You et al. [Appl. Phys. Lett. 115, 043104 (2019)].